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NLG Users Repair Logs and Other Ramblings. Request your very own topic. Just ask any site staff. => Channelmaniac's Arcadecomponents' Old School Repair Logs => Topic started by: channelmaniac on May 07, 2014, 08:34:32 PM

Title: Midway Games
Post by: channelmaniac on May 07, 2014, 08:34:32 PM
Fixed: MK3 Ultimate
Symptom: Dead

Physical inspection of the board turned up a large (20 gauge!) wire patch on the EPROMs. Replaced that patch with a 30 gauge Kynar wire wrap wire patch. Found one other gouged trace that was broken in 2 places and gouged off the board by what appeared to have been a huge soldering iron. Board booted but had a ROM error. Replace ROM U132. Game played but had scratcy audio. Resoldered the audio output IC as it had been physically hit and the solder joints had cracked.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:34:44 PM
Fixed: NBA Jam
Symptom: Scratchpad RAM Error

Board would power up with a Scratchpad RAM Error for UJ7. Replaced the bad chip, a 44256 DRAM, with a socketed replacement. Board would then power up and run but would intermittantly give an error on Video RAM UA11.

Replaced the VRAM IC at UA11 - part # MT42C8128, a 256 x 8 SAM + 128K x 8 RAM dual port video RAM chip. Chip is hard to find but can be found on some old Sun Microsystems frame buffer (video) cards from the early 90s. (In this case a Weitek Power 9000 based card by Megatek)

Ran board through the built-in burn-in tests and played a couple of games.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:34:57 PM
Model: Ms. Pac Man
Symptom: Garbage on screen

Replaced the ROM at location 6H. It had 5 pins broken off of it and was half way out of the socket. Straightened the pins on the V-RAM addresser daughterboard and reinserted it. It had come loose in shipping. Replaced the zip tie holding the daughterboard in place.

The ROMs on Ms. Pac Man are 2532 and NOT 2732.

To retrofit a 2732 you must rewire 3 pins.

2532:
18: CE*
20: Vpp
21: A11

2732:
18: A11
20: CE*
21: Vpp

This can be done by stacking 2 sockets. make the wiring change between the 2 sockets so the EPROM fits in and it all fits into the board.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:35:07 PM
Model: Galaxian
Symptom: Large color stripes on screen

Board was missing the U and W ROMs. Burned replacement 2716 EPROMs to bring the CPU to life. Large color stripes would change periodically. The ROMs at J1 and L1 were bad. Burned replacement 2716 EPROMs and the board showed a perfect screen.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:35:20 PM
Model: Galaxian
Symptom: White screen

Game gave a full white screen and no video artifacts. CPU was rebooting itself and the data lines were in a repeating loop for signals. Replaced bad ROM at Z. Pin 13 was broken on the chip.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:35:29 PM
Model: Ms Pac Man
Symptom: Rebooting at random

Replaced the CPU socket and socket J1 for the ribbon cable on the daughterboard.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:35:40 PM
Model: Ms Pac Man
Symptom: Will not boot. Single glitching character on screen.

Ms. Pac Man will normally cycle through characters while doing a self test. This board was stuck on 1 character but was glitching that character continuously.

Replaced bad ROM at 6J and the board would try to boot but come up wtih garbage on screen.

Replaced a bad 2114 SRAM to finish the repair.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:35:49 PM
Model: Pac Man
Symptom: Garbage on screen. Screen is flipped. No audio.

Board had squished looking blobs for ghosts, text, and fruit. The maze looked as if it were Atari 2600 quality. Very blocky.

Replaced a 74LS174 at 1H to fix the garbage graphics. Pin 9 on it was dead. Replaced 74LS259 at 8K to fix the flipped screen problem. This chip also controls the 74LS273 at 2M for audio but now the speaker would output garbage noise. Replaced the 74S89 RAM IC at 2L to fix the sound problem.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:35:59 PM
Model: Pac Man
Symptom: Garbage on screen. Dead.

4 ROMs failed checksum. Burned new EPROMs for 5E, 5F, 6H, and 6J and tested the board.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:36:11 PM
Model: Pac Man
Symptom: Dead, Garbage on screen.

Fixed a bent pin on ROM 6F. Roms at 6E, 6H, 5E, and 5F were bad. Programmed new ROMs and tested board.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:36:20 PM
Model: Pac Man
Symptom: Colors wrong on maze

The PROMs at 7F and 4A were for a Pac Man Plus and not a Pac Man. Burned new PROMs and tested board.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:36:32 PM
Model: Pac Man
Symptom: Maze would disappear and ghosts would all be blue.

This one took awhile to track down. The maze would be there then disappear. Then it would be fuzzily fading out from top to bottom. Very odd symptoms. When the maze disappeared the ghosts would all be dark blue in color and the text describing their names would be the same shade of blue.

Found pin 1 on 5B / 5C, pin 3 & 5 on 5A, and pin 1 on 4D were floating. These pins are tied to +5v through a 1k ohm resistor. Replaced the 74LS194 at location 5C to fix the board. This chip was pulling too much current on pin 1.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:36:43 PM
Model: Pac Man
Symptom: Sparkling garbage in text and maze

The high speed RAM is used for moving graphics, not the maze. Since the moving characters were perfect the RAM was good. Traced it back to the character EPROM at 5E. EPROM tested good in a programmer but would not run at speed. Replaced the EPROM to fix the game.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:36:54 PM
Model: Pac Man
Symptom: Garbage on screen.

This was another board that had squished looking blobs for ghosts, text, and fruit as if it were Atari 2600 quality. Very blocky.

Checked the 74LS174 at 1H and it was stuck low. The chip was constanly in clear mode. Checked the circuit and found multple chips hooked to that line, labeled "P" on the schematic. Replaced the 74LS107 IC driving that line and played the game.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:37:03 PM
Model: Pac Man & Mrs. Pac Man
Tip: Burning new PROMs

When burning PROMs for this game, there are some chips that CAN be successfully substitued.

The 82S126 at 1M and 3M CAN be replaced by an 86S129 PROM.

The 82S126 is Open Collector outputs and the 129 is Tri-State.

I have not tried subbing out the 129 for the 126 at location 4A.

The 82S123 at location 7F is the video output PROM. It CANNOT be replaced by the 82S23. It will technically work but does not have enough current drive and the output is very low resulting in a VERY dim display on the monitor.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:37:12 PM
Model: Pac Man
Symptom: Dead. Horizontal lines through playfield, but not scores or level/men remaining area.

Replaced 3 ROMS with corroded off legs to fix the dead board problem. The lines looked like a failure in the high speed video memory. Every chip I checked the Data Out line with the logic probe resulted in the signal going nuts on the probe AND on the screen. The well calibrated finger to the bottom of each chip made the screen go nuts. Checked the Data In lines and they were OK. The Data Out connections went from the RAM chips to the 74LS75 IC at location 3D and were tied high by RM2. Touching either of these made the display go nuts.

Checked RM2 (5 pin SIP resistor network. 4 1k resistors with a common to pin 1) which was to tie the DO lines high. There was no connection between each resistor and pin 1. Replaced RM2 with one from a parts board to fix the video.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:37:21 PM
Model: Galaxian
Symptom: Bad RAM 2 error message on screen

This error message is related to the RAM at 3F or 3H. Replaced both RAM chips then the board came up with a Bad RAM 3 message. This indicates a bad RAM at 4FH or 5FH. Replaced the RAM at 5FH to fix that error. Board then came up with a Bad ROM message. Reseated the ROM daughtercard to fix that error.

Board then came up with horizontal lines across the screen. Burned a new character EPROM at 1H to fix the lines.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:37:29 PM
Model: Galaxian
Symptom: Bad RAM 1

This indicates a problem with the RAM at 7N or 7P. Replaced both RAM chips to fix the error. The game had horizontal lines across the screen. Replaced the ROMs at 1H and 1K to fix the lines.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:37:38 PM
Model: Galaga
Symptom: RAM 2L Error

This board was frustrating. RAM 2L bad. Replaced it. RAM 2H bad. Replaced it. RAM 2L bad... RAM 3L bad... RAM 3H bad...

Cleaned the pins on the custom IC at 1H on the video board to fix the error.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:37:48 PM
Model: Galaga
Symptom: No characters on screen

The player and enemies were both missing. Cleaned the pins on the custom chips on the video board.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:38:07 PM
Model: Galaga
Symptom: Cannot control Player 1. Enemies go in circles then disappear

This was odd. Game self tested fine and coined up. Player 1 controls were non responsive. Couldn't fire and couldn't move. When enemy ships came down the last one tried to peel away and would go in circles for about 10 seconds then disappear. Once it disappeared the next wave came and the last one repeated the circling and disappearing act.

Checked the ROMs on the CPU board. Found EPROM 3300 was for revision 2 of the Galaga software while the rest of the ROMs were for revision 1. Replaced the EPROM with one holding the correct code to fix the game.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:38:16 PM
Model: Galaga
Symptom: Random lockups

Board would lock up even during self test. Could tap on the board and cause it to lock up.

Replaced the 3 Z80 CPU sockets. The old TI sockets were making intermittent contact with the chips.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:38:30 PM
Game: Galaga
Symptom: Locks up after the initialization explosion sounds

The ROMs on this board were Namco instead of Midway with the exception of the ROM at 3M. Replaced it with one programmed with the Namco version of code.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:38:39 PM
Game: Galaga
Symptom: Faint digital artifacts instead of music.

Resistor pack RM2 was broken. Replaced resistor pack and artifacts were gone. Music was still missing.

The 74LS273 chip at 3B had inputs but no outputs. The clear line was being held high, which is correct. The clock line was cycling during explosions but when high when music was supposed to play. This line is controlled by the PROM at 5C.

Replaced the PROM and the music played as it should.

Read the PROM in the EPROM programmer (7611 which crossed to an 82S129) and it read good. The code didn't change when reading multiple times. Ran the code through ROMIDENT - It's a PAC MAN PROM chip for location 3M. Someone stuffed the wrong PROM on the board.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:38:48 PM
Model: Galaga
Symptom: Passes RAM tests then instead of explosion sound & crosshatch it dies

Replaced 3 CPU sockets. Board would then get to the point where it says RAM OK then the screen slowly paints white then the board resets.

Checked the EPROMs. Found 2 were for Galaga set 2, 2 were for the fast shoot hack, the ROM at 3J was bad, and the ROM at 3E was for Bosconian!

Replaced the ROMs and the board came right up.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:39:04 PM
Model: Galaga
Symptom: No sounds except explosions

Sound PROM at 5C was incorrect. It had a PROM for 1D in the socket.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:39:17 PM
Model: Galaga
Symptom: Reboots constantly

This is different than the bad CPU socket problem in that it wasn't stuck at RAM OK but rather as soon as the crosshatch then the text came on the screen it rebooted. The Reset line on CPU #2 and 3 came active for a VERY short period of time then the game reset.

Swapped out the CPU sockets. Subbed out the custom chips. Nothing. On a whim I turned off each DIP switch and found by playing with them that when DIP switch #3 at 6J was on it would cause the system to lock up when running or to constantly reset when booting.

Replaced the 74LS151 at 4K and the 74LS368 at 5A. Problem still there. Checked the EPROMs again. They were all checking good on the programmer. Swapped out the first 2 program EPROMs. Nothing. On a whim I burned a new set of Williams EPROMs (these were Namco) and swapped out all the EPROM.

Problem fixed.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:39:30 PM
Model: Galaga
Tip: Replacing PROMs

The PROMs used on the board are Harris 7611. These are 256 x 4 bit bipolar PROMs.

Other PROMs can be used to replace this one, including:

    5623
    6301
    7052
    74S287
    82S129
    93427
    AM27S21
    F93427PC
    63S141


I have tubes and tubes of Fairchild's 92446 - a 512 x 4 bit bipolar PROM. If you take the code for the 256 x 4 bit PROM and duplicate in the upper half of the PROM these can successfully be substituted for the smaller PROM.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:39:44 PM
Model: Galaga
Symptom: flickering garbage on screen.

Board had been worked on before by a ham fisted technician. Removed their soldering work at 2K, 2L and 2M. Cleaned up the bridged soldering mess under the socket at 2L, installed new sockets, and installed new chips.

Board now had a solid white screen with garbage characters on the top row. During the attract play when the boss ship captures the player's ship that part is visible on the screen under the garbage but the ray is mixed up.

Pin 19 on 2L was stuck high. The input, on pin 18, was missing because of a damaged platethru. Ran a wire jumper and played the game.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:39:56 PM
Model: Galaga
Symptom: Multiple graphics problems

Another "attempted repair" by a ham fisted technician. This board had flickering video, incorrect text, bad colors, double characters, and a lot of vertical lines through the screen.

Found a bad trace connecting Pin 1 of 4A. 4A drove address line A9 for 4 of the video RAM chips. Fixed the trace to cure the vertical lines problem.

Found a bad trace connecting pin 1 of 3D. Patched the trace to fix the double characters.

Tapped the board and found that if the EPROM at 4L was tapped the screen flickered and the text changed. Replaced the bad socket to fix the flickering and incorrect text problem.

Repaired a bad trace on the video output resistor ladder to fix the color problem.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:40:17 PM
Model: Galaga
Symptom: Multiple video problems

Another board from a ham fisted repair attempt.

Board had no video. Cleaned the pins on the custom chips at 00xx, 7xxx, and 02xx. Repaired bad pins on those chips and piggybacked an extra socket on the 00xx and 02xx chips to protect the fragile pins.

Board now has video but the video has blue lines through it. Replaced a broken SIP resistor pack at RM5 to fix the blue lines.

Board now has video but the layout is wrong. Ships are doubled, text and player ships stack vertically up the left side of the screen and the crosshatch has many tiny squares down the left side. Patched a trace between pin 11 of the 00xx and pin 21 of the 07xx chips.

Board now has video but colors are wrong. Replaced all the cut and resoldered resistors in the output ladder. Patched 3 damaged traces. Now the video looks great and I set a new personal high score.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:40:26 PM
Model: Galaga
Symptom: locks up

2 boards with the same symptoms... Passes RAM/ROM tests, makes the explosion sounds, then locks up randomly. When it freezes up the characters on the screen may or may not disappear. Most of the time the screen will then flip upside down. It might play for a minute or 3 then it will start doing strange things.

Symptoms:

    Starfield starts flickering fast
    Enemies wings move a LOT faster
    Enemies MOVE a lot faster


Tested the ROMs with the EPROM programmer and by substitution. Cleaned the custom chip legs and swapped out the 7xx, 6xx, and 51xx chips. Replaced the ROM sockets and CPU sockets on one of the board sets. The logic probe showed the CPU at 4E was halting. I noticed that when shorting the IRQ pin to D0 (15 to 16) on that CPU the board would run (strangely) and not lock up. Replaced the CPU on each board and played a couple of games.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:40:35 PM
Model: Pac Man
Symptom: Blocky graphics

Pac Man would coin up and play, but the grapics on the screen were nothing but large squares & blocks.

Replaced EPROMs at 5E and 5F.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:40:45 PM
Model: Pac Man
Symptom: Flickering garbage graphics. Game will not play blind

The VRAM Addresser (284) module was not in the socket correctly. Removed module and discovered that 2 pins were missing from the bottom. Replaced the socket on the bottom of the module, reinstalled it, and played a few games.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:40:55 PM
Model: Pac Man 11-in-1
Symptom: Dead. Burned power connector

Replaced the 4 power traces on the connector with copper circuit tape. Board would power up but was dead. The CPU and EPROM board added on as part of the 11-in-1 mod had bent pins on the bottom socket. Replaced the socket and played a few games to test the board.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:41:09 PM
Model: Pac Man
Symptom: Dead. Burnt edge connector. Black screen.

Repaired the burnt edge connector with copper circuit tape. Powered up the board to find it was dead.

Checked the reset line on the CPU. It was stuck high. Checked pin 9 of IC 9C and found the reset switch was working properly. The IC at 9C was not receiving the VBLANK signal on pin 2. Traced this back to the 74LS74 at 5M. Found the 16V, 32V, 64V and 128V clocks were missing. Further troubleshooting revealed that all of the V clock signals were missing.

Checked the IC at 3N and found the 16H and 64H signals were present on pins 11 and 12. Replaced the IC, no change. If pins 11 and 12 are shorted together, the game will boot but will have the screen divided into 9 identical small screens. checked the 74LS161 ICs at 3R and 3S. The IC at 3R had identical outputs on pins 11, 12, and 13 instead of divided clock signals. Replaced the IC at 3R and played a few games to test.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:41:25 PM
Model: Ms. Pac Man
Symptom: Dead. Had shipping damage due to insufficient packing and no zip ties on daughtboards.

Board arrived with shipping damage. Once damage was fixed, the board was still dead.

The VRAM Addresser and Z80 Sync Bus Controller modules were both floating around loose in the box. They weren't zip tied into place.

Removed the bent up socket on the bottom of the VRAM Addresser board and replaced it. Straightened the pins on the Z80 Sync Bus Controller board. Board symptoms: Dead.

Replaced bad CPU. Game would play but had no audio. Used the logic probe and found audio signals at the output of the sound section. Used the oscilloscope and verified audio was getting to the final amplifier IC's input pins. Replaced the bad audio amplifier IC and the filter cap on the 12v line.

It's uncommon to have a blown audio amplifier IC. If a Pac Man series or Galaxian series board is put into a Neo Geo multislot cabinet with a JAMMA adapter, the audio IC will get finger blistering hot and burn out. The multislot MVS boards are wired differently and this stresses the audio output IC.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:41:35 PM
Model: Galaxian
Symptom: Constant background tone when playing

Galaxian is supposed to have a varying tone in the background when playing. It gets faster and faster as the game is played. On this board it was only playing a single continuous tone.

The troubleshooting guide points to a problem with a 555 timer and the 2 GE6015 transistors. The 555 timer had already been replaced by the customer. Checked the 2 GE6015 transistors and they were good.

Checked C15, C16, R15, R16, R17, R18, R20, and R21. All checked good. Swapped the 555 timer chip since it was CMOS and the original part wasn't. No change. Checked the resistance from pins 2/6/7 of the 555 to +5v and ground. It read 1200 ohms to both power and ground. Swapped out the LM324 quad op-amp chip to repair the board. It connected to pins 2/6/7 of the 555 timer chip and had an internal short to power and ground on the input.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:41:44 PM
Model: Galaxian
Tip: Transistor cross reference

The Galaxian sound subsystem uses 2 GE6015 transistors to oscillate the background audio. These transistors are no longer made and are not in the NTE cross reference book.

They can be successfully replaced with the easy to find 2N3906 transistors.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:41:52 PM
Model: Mortal Kombat 4
Symptom: Board had multple RAM failures and no video sync

Replaced U74, a surface mount 74LS07 and replaced a burnt zero ohm resistor on the video ground to fix the video sync problem.

Resoldered U66, U32, U62, and U63 then resocketed U48 to fix the RAM issues and random reboot issues. Board can now be jostled briskly without rebooting.

Reset button was dead. It had liquid (rodent?) damage. Cleaned the board and replaced the switch.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:42:01 PM
Model: Pac Man Jr.
Symptom: Burnt edge connector.

Repaired connector traces with copper trace tape and tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:42:14 PM
Model: Galaga
Symptom: Dead. Stuck in reboot loop.

Removed a 68B09 CPU from socket 4H and installed the proper 51xx custom Namco chip. Replaced the 3 Z80 CPU sockets and the 6 ROM sockets. Board would still either be stuck in a reboot loop or act dead. When it acted dead the CPU was stuck in a reset loop. If the board was slightly flexed it would try to boot.

Replaced a bad socket on the 7xx chip. The VBLANK* signal was not getting to IC6A, pin 1, to keep the watchdog signal from resetting the CPU. Reset the DIP switches to factory settings and tested.

The board was now missing all text on the screen except the very top row, which was green instead of red. When playing game the flags showing the level were the wrong color and missing lines and the line showing the credits was missing.

This is handled by the EPROM at location 4L. It is fed by a 74LS273 at location 2L and 74LS86 at location 2N. These were good, the EPROM tested good by a programmer and by substitution. All the signals were correct on the custom chip at location 4H. The IC at 4H outputs the control signals for those images out pins 11 and 12 to pins 5 and 6 on IC 2N, a PROM. Checked the PROM and found that pin 9 was folded under the chip. This is the D3 output. Straightened the pin and tested the game.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:42:24 PM
Model: Galaga
Tip: Stuck in reboot

If the DIP switch for Video Freeze (6J, switch 5) is left on and the game restarted it will be stuck in a reboot loop until the switch is turned OFF. The effect is different than when you have bad CPU or ROM sockets on the CPU board where it shows RAM OK then reboots. In this case, it is showing ROM OK, RAM OK, and the rest of the normal text before suddenly rebooting.

If after replacing those CPU and ROM sockets (which should be done on ANY Galaga game that still have factory sockets) the board is still rebooting then check that switch. You'll save yourself headaches.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:42:40 PM
Model: Galaga
Symptom: Multiple problems. Board had been worked on before.

Board would boot but had no explosion sounds and would not accept inputs properly. Sprite graphics were missing every other vertical line and there were vertical blue noise 'tails' on the bottom of the screen.

CPU board: Replaced missing 00xx and 06xx ICs. They were in the box with the board but were not installed and had missing pins. Repaired broken pin 28 on custom IC 55xx to fix the input and sound problem.

Video board: The sprite problem would come & go with flexing the PC board. Replaced a bad socket and trace on pin 3 of 1C. Resoldered the SRAM socket on 2148 SRAM at 6B. The ground pin was not soldered properly. Resistory pack RM7 was bad and causing the blue vertical streaks.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:42:50 PM
Model: Galaga
Sympom: Dead. No video output.

Board was previously worked on and had problems on both the CPU board and Video board.

CPU board: Fixed one badly jumpered trace. Replaced a bad EPROM at 3K, the D1 and D2 lines were shorted internally. Replaced bad sockets on the CPU at 4M and the Namco custom chips at 4D, 2L, 2J, 2H, and 2E.

Video board: Cleaned board. The 6MHz clock signal was not getting to pin 1 on the 02XX IC at location 4H. Replaced bad sockets on Namco custom chips at 1N, 1L, 1H, and 4H. Fixed a broken leg on the 07XX chip at 1N and cleaned the legs on the custom ICs at 1N, 1L, 1H, and 4H. Cleaned the legs on the SRAM IC at 1K to finish the repair.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:43:00 PM
Model: Ms. Pac Man
Symptom: Dead

Removed the daughterboard and powered up the system without it to isolate problems. Some of the normal startup RAM tests are occurring but when it is supposed to switch to another area of RAM it reboots. Rebooting is NOT being kicked off by the watchdog timer.

Found that when the board was flexed it would boot normally. Found a cut on the trace coming from pin 3 of the 74LS367 buffer chip at 6R. This was the AB10 signal line feeding the 74LS139 2 to 4 selector that controlled the CS* (Chip Select) line on the 2114 SRAM ICs. Repaired the trace and the board would play as a Pac Man game with corrupt characters, normal since the Ms. Pac Man ROMs were in 5E/5F.

Replaced a broken 40 pin connector on the daughter board ribbon cable, reassembled the game and tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:43:09 PM
Model: Galaxian
Symptom: No Sync

Replaced a bad 74LS08 at location 6H and tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:43:18 PM
Model: Pac Man
Symptom: Dead

Board had attempted repairs already done.

There were a few pins on the machine pin sockets from the attempted repairs that weren't fully soldered in. Once that was done the symptoms looked like bad RAM. If the board was flexed it would give different bad RAM symptoms - All zeros, colored text/graphics, and even booted once.

Broke out the pscilloscope on this one... the upper data bits were horribly garbled. Replaced the 6 2114 SRAM sockets and tested. Board died during extended testing. The Reset* line died. Without the proper reset pulse at power on the Z80A CPU will never start.

Replaced a 74LS161 at location 9C to fix the reset circuit.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:43:27 PM
Model: Cruis'n USA
Symptom: Dead

Board was paired with a Cruis'n World and someone tried to troubleshoot by swapping parts.

Sorted out the ROMs with an EPROM programmer and eplaced 1 missing program ROM. Swapped the correct PALs back on the board and tested the game.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:43:37 PM
Model: Pac Man
Symptom: Garbled sound.

This board had been worked on before. There were many patches on this board and the IC at 1N had many traces and pads pulled. It also had many of its holes DRILLED out.

Removed a short between pin 5 and 11 on the 7489 RAM at 2L to fix a portion of the sound.

Removed short between pin 8 of 1N and R4. Patched open trace between pin 9 of 1N and R4. Now the sound disappeared. This was because one of the inputs on the digital switch was shorted directly to the resistor on the output.

Patched open trace between pin 7 of 1N and ground. Noticed that 1N was incorrect. Replaced the 4006 at 1N with a proper 4066 IC and redid many patches on the board then played a few games to test the board.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:43:49 PM
Model: Galaga
Symtpom: No sound and graphics problems

Installed a renew kit (new 24/28/40/42 pin sockets... resistor packs did not need replacing), cleaned all chip legs, and reinstalled the chips into their new sockets. Tested game. Game now works, with sound, but has a strange graphic anomaly: The player and enemy ships are all tilted to 45 degrees, player explosions are divided into four pieces, and enemy explosions are numbers 20 over 31. If the enemies are tilted to the left the numbers are upside down and if they are tilted to the right the numbers are right side up.

Checked the Graphics ROMs on the video board. Pins 1 and 2 were stuck low with very rapid racing pulses. Checked the 74LS153 at 1B and found it had normal inputs but bad outputs. Replaced the IC and tested the game.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:44:00 PM
Model: Galaga
Symptom: Missing some blue on motion graphics and random blue streaks on board

This was a very tough one to track down. The board worked fine until an extended burn-in was done. Swapped out the motion RAM (8 x 2147), the resistor packs that hold the data lines high, 1 PAL, and a couple other 74xx chips. Replaced the 74LS298 at location 5B to fix the missing blue. This chip multiplexes the 8 data output lines from the motion RAM into 4 for mixing with the text graphics and later with the starfield.

The random blue streaks was just as tough to track down. Checked the 74LS365 chips at 5A and 6A, swapped out 2 of the replacement Video RAM chips, and checked the 74LS157 at 4A. (Yes, 4A. It says 5A on the schematic, but there's a 74LS365 at that board location. The schematic has an error.) Traced the problem back to pin 10 on the 74LS20 at location 3A which feeds the LS157. Pin 10 is the 6MHz* clock. Swapped the 07xx IC to no change. Replaced the 74LS368 IC at location 3N to finish the repair.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:44:10 PM
Model: Ms Pac Man
Symptom: Hacked and missing parts

Board was missing the Z80 Sync Bus Controller and Z80 CPU. Replaced missing parts and the board worked, but had an odd problem with the text on the top and bottom lines of the screen.

The text was cut down the middle and repeated on the right side of the screen. "1UP   HIGH" was repeated on the left side and right side of the screen. The remaining text for HIGH SCORE and 2UP was missing. Same thing with "CREDIT 0" on the bottom.

Pin 4 of the middle 74LS157 was supposed to connect to pin 2 of the middle 74LS257 on both sides of the connector that plugs into the main board. Removed a blob of solder that was an attempted repair and soldered in a jumper to finish the repair.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:44:19 PM
Model: Pac Man
Symptom: Random reboots

Cleaned the Z80 Sync Bus controller chip's pins. This was the old custom chip version with tarnished legs, and not the daughterboard. Replaced the bad CPU socket and ROM 5E sockets to finish the repair.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:44:29 PM
Model: Pac Man
Symptom: Dead hacked board.

Board was poorly hacked and had jumper wires that were not soldered on one end.

Removed the 8 EPROMs for the Ms Pac Man bootleg hack, removed several jumper wires, fixed 5 cut traces, and installed freshly programmed Pac Man ROMs in rows 5 and 6. Tested game.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:44:38 PM
Model: Ms Pac Man
Symptom: Garbage on screen

Board was reported as dead with garbage on screen, but booted fine on the bench. If the ribbon cable to the daughter board was bumped, the board would reset. Replaced bad 40 pin socket on the daughter board and tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:44:48 PM
Model: Ms Pac Man
Symptom: Dead: Garbage on screen, random audio tones

Board had a hacked ribbon cable that had at one time burned a wire. Also, a chip on the Z80 Sync Bus Controller had been replaced.

Checked the daughter boards. The VRAM Addresser had a bent pin 13. Straightened pin and reinserted the module. Checked the Z80 Sync Bus Controller and found that pin 14 had burned. Cleaned pin 14 and replaced both the Sync Bus Controller socket and the CPU socket.

The game would now run, but the moving characters were doubled - all the ghosts were blobs with 4 eyes and Ms Pac was made with 2 upper halves. Replaced 2 noisy 74161 and 1 noisy 74LS10 that had garbled signals on some pins. This cleaned up the signals, but didn't fix the issue. Replaced a bad 74LS157 driving the Character ROM address lines to finish the repair.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:45:01 PM
Model: Galaga
Symptoms: Graphics corruption

Replaced every tall, flat style resistor pack and tested. These packs are sources of a lot of problems on Galaga boards.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:45:15 PM
Model: Galaga
Symptom: Dead. Garbage on screen.

Installed all new 24/28/40/42 pin sockets. Cleaned the custom chips. Board would run but would die when hot. Replaced CPU at 4M to finish the repair.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:45:25 PM
Model: Ms. Pac Man
Symptom: Constant reboot. Trash on screen

Board would go through the normal boot cycle but would reboot before it would finish. There were random vertical lines on the screen. Replaced bad 74LS245 at 4H. Board would still reboot, but garbage was gone. A close look showed an error message flashing just before reboot. Replaced bad 2114 at 4P to finish the repair.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:45:34 PM
Model: Galaga
Symptom: No coin inputs and faint garbage lines on screen during self test

Replaced bad resistor pack at location RM10 to fix coin inputs. Replaced EPROM sockets and 42 pin socket on the CPU board. Replaced all 24/28 pin sockets on the video board. Tested. Replaced bad PROM at location 2N to fix the faint line issue and retested board.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:45:44 PM
Model: Galaga
Symptom: RAM 0L error

Replaced all resistor packs and 24/28 pin sockets on the video board. Cleaned legs on the custom chips. Board then fired up with a 2L error and random garbage on screen. Garbage would change when pins 1-7 were checked on the SRAM with a logic probe. Replaced bad 04XX chip and tested. Replaced all 24/28/40/42 pin sockets and all of the resistor packs on the CPU board. Tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:45:52 PM
Model: Pac Man
Symptom: Dead

Board was part of a group of 7 boards sent in for repair. It would not try to boot and was stuck in watch dog. Replaced CPU socket then board would try to boot but fail. Checked the ROMs and found Pac Man Plus ROMs on the board. Reprogrammed the 4 program ROMs and 2 character ROMs and tested. Board had Pac Man PROMs so the colors were OK.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:46:05 PM
Model: Pac Man
Symptom: Dead

Board was part of a group of 7 boards sent in for repair. It would not try to boot and was stuck in watch dog. Checked the ROMs and found a rotted pin on 6E and a mixed set of bootleg ROMs for the remaining 3 on row 6. Replaced the bad ROM and reprogrammed the other 3 program ROMs and tested. Board had a Pac Man Plus PROMs at 7E which caused the board to output incorrect colors. Replaced the PROM and tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:46:15 PM
Model: Ms Pac Man (boot)
Symptom: Dead

It was an original Pac Man board, but hacked with 2 extra ROMs to run as Ms. Pac Man. Board would boot, but was stuck in reset with nothing showing on screen. Four of the 8 data lines were dead on the Z80 Sync Bus Controller. Replaced bad (non-original) socket on the Z80 Sync Bus Controller. Board would boot to text garbage on screen. Fixed 1 broken trace between the Z80 Sync Bus Controller and the CPU. Board would then boot, get to the Memory OK screen, then reboot continuously. Repaired a broken trace for A11 between ROM 6J and 6K. Board then booted and ran, but the background maze would randomly disappear. Cleaned the pins on the ROM at 5E to finish the repair.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:46:44 PM
Model: Ms Pac Man (boot)
Symptom: No sound. Graphics issues.

It was an original Pac Man board, but hacked/converted with 2 extra ROMs to run as Ms. Pac Man. Board had no sound and displayed flashing garbage for the pink ghost. Also the pink ghost was 1/4" lower than the other ghosts. Replaced a bad RAM at 3F to fix the graphic corruption. The display looked normal but the ghosts were moving in a jerking manner and the display would disappear after a minute of being on. Replaced a bad RAM at 3H to fix the movement of the ghosts and replaced a bad 74LS157 at 5A to fix the disappearing display. Replaced a bad 74LS273 at 2M and the sound was partially restored. Instead of no sound, it made popping noises where sounds were supposed to be. Replaced a bad PROM at 3M to finish the sound repair. Repaired a burnt edge connector and tested the game. Found horizontal lines through ghosts & Ms. Pac Man. Replaced bad socket at 5F and re-tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:46:55 PM
Model: Ms Pac Man
Symptom: Dead

Board had some shipping damage and when on the bench was not stuck in watchdog. Straightened many bent pins on the Z80 Sync Bus Controller Module and the VRAM Addresser Module. Checked the 74LS161 chips at 2R/2S and 3R/3S. The chips at 2R/2S had no outputs. Replacing 2R/2S had no effect. Replaced 2P to no effect. Replacing the 74LS74 at 5M fixed the game. The outputs on 5M were there, but incorrect, causing the 74LS161 chips to not work. Installed missing zip ties to hold the 2 modules in place before returning to customer.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:47:04 PM
Model: Ms. Pac Man
Symptom: Dead - garbage on screen

Board had a strange hack with a 74LS257 on it. The wires for the 257 were not all attached to the board. Removed the hack, cleaned the insides of the legs on the mask ROMs and fixed 2 bent pins on the VRAM Addresser module. Fixed 6 burnt power supply fingers on the edge connector and installed an edge connector trace for the missing player 1 start connection. Replaced missing zip ties on the 2 daughter cards and tested board.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:47:12 PM
Model: Galaga
Symptom: White screen. Dead.

Board had been worked on before. Installed a renew kit (new 24/28/40/42 pin sockets & all resistor packs) on the CPU board and found that 2 of the 08xx chips on the CPU board had pins bent under them. Repaired the pins as they will snap off when straightened, cleaned all the custom chips and tested. Game now worked but had no starfield and had blue lines on the screen.

Installed the renew kit on the video board, replaced the starfield generator, cleaned the pins on the custom chips and tested. Replaced the 2147 at 6L to fix the blue line issue and re-tested board.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:47:22 PM
Model: NFL Blitz 99
Symptom: Dead Short

Replaced 2 shorted tantalum capacitors on the -5v line and tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:47:32 PM
Model: NFL Blitz 99
Symptom: Will not work in Standard Res mode

Tested the DIP switches and found that U8 Switch 2 was stuck open. Replaced the surface mount DIP switch with one from a parts board and tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:47:41 PM
Model: NFL Blitz 99
Symptom: Buzzing sounds from speakers, won't enter test mode

Board was VERY dirty. Cleaned board and replaced both sets of DIP switches. Audio issue was very odd. The hard drive, video, and any other operation could be heard through the speakers. The noise could be seen as ripple on the +5, -5, and +12v lines and No audio from the game was present. Pulled the D/A converter with no change. Pulled the audio op-amp and noise disappeared. Replaced the op-amp and reinstalled the D/A converter then tested.

The bad op-amp was overdriving the audio output IC and causing the loud noise. The overdriving also caused large current pull from the power supply which showed as ripple on the outputs and as noise through the speakers.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:47:49 PM
Model: Galaxian
Symptom: Distorted characters/text and text wrapping around right side of screen

All address and data lines were present but not proper on the character ROMs. Shorting A1/A2 together made the garbled blocks look more like text. Checked the 74LS273 at location 2M and found output pin 9 was dead and pin 6 was strobing. Replaced the IC and tested the game.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:47:57 PM
Model: Pac Man
Symptom: high pitched beeps and blips instead of normal sounds

The beeps and blips occurred at the same time and cadence as the normal sounds. Replaced the 74LS273 and checked the PROMs by both checksum and substitution. Replaced the 2 bi-polar RAMs. No change. Compared signals to a working board and found all the enable lines were correct. Replaced the 74LS283 at 1K to fix.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:48:05 PM
Model: Galaga
Symptom: Reboots, crashes

Installed renew kit and replaced 1 cracked 1K resistor. Tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:48:23 PM
Model: Galaxian
Symptom: Dead. Garbage on screen.

Reseated the ROMs. Address lines were stuck high. Data lines were dead. CPU stuck in watchdog reset. Replaced bad Z80 CPU and tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:48:32 PM
Model: Ms Pac Man
Symptom: Dead. Garbage on screen.

Reseated the Z80 Sync Bus Controller. It was in the socket incorrectly and off by 1 set of pins. Audio had a repetitive whump whump whump type sound like a helicopter. Replaced C51, a 330uf @ 16v cap to fix the audio. Tested game.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:48:42 PM
Model: Mortal Kombat II
Symptom: Garbage on screen

Board failed video RAM tests. Reseated UB21, replaced bad battery holder, and tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:48:54 PM
Model: Mortal Kombat II
Symptom: Game will not start

Board passes self tests and coins up. When P1 or P2 start button is pressed the game immediately shows "game over" on screen. Reflowed surface mount memory access controller chip at UE13 and tested board.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:49:04 PM
Model: Ms Pac Man
Symptom: Dead. Garbage on screen.

Board was stuck in reset. Replaced bad 74LS74 at 5M. Board now had garbage on screen and intermittent reset. Cleaned the legs on the program ROMs and replaced the ROM at 6J as it had 2 broken legs. Board then had multiple vertical images and would not reset consistently. Replaced bad 74LS161 at locations 2S and 3S. Board played but would reset when jostled. Replaced the socket on the daughter board and both ends of the ribbon cable to finish the repair. Tested board.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:49:13 PM
Model: Ms Pac Man
Symptom: Stuck in loop

Board was stuck trying to boot. It would occasionally flash the number "1" on the screen. Replaced the SRAM at 4R. Board then would try to go through self tests and would reboot half way through them. Replaced the SRAM IC at 4L. Tested game.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:49:24 PM
Model: Ms Pac Man
Symptom: Dead. Garbage on screen.

When the daughter board was removed and the Z80 placed on the main board, the game played as Pac Man with a garbled Ms. Pac. (which is normal!) Checked the ROMs on the daughter board and replaced both U5 and U7. Tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:49:33 PM
Model: Galaxian
Symptom: Dead

Board had damage from a previous attempted repair.

Board would try to boot but just make beep/blip noises and repeating garbage on the screen. Cleaned the legs on all the ROMs. ROM W on the daughter board had a broken leg. Patched the bad leg and replaced a bad ROM U on the daughter board. Chip at 9B had a pulled trace that needed patching. Patched the trace then replaced a bad 74LS367 chip at 8D. Board would THEN try to boot but had a RAM Error. Replaced a bad RAM chip at 5F. Board then booted but had color stripes on the screen and no stars. Replaced bad ROM at 1H to finish. Tested game.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:49:42 PM
Model: Ms Pac Man
Symptom: Garbage on screen. Plays

Board had flickering garbage on screen but played normally. Isolated problem to the VRAM Addresser. Pins were good. Removed a wire shorting 2 pins from the top of the board and replaced a bad 74LS257 IC to finish the repair.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:49:52 PM
Model: Ms Pac Man
Symptom: Dead. Garbage on screen.

Board had physical damage to the ribbon cable. Removed Z80 CPU from the daughter board and installed it on the main board. Game played but with the expected graphic issues. Assembled a new ribbon cable, installed it, and tested the game.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:50:00 PM
Model: Pac Man
Symptom: Characters only move around bottom right quarter of the screen

Board had a 6-Pac mod installed.

Cleaned the edge connector and reinstalled the 6-Pac ROM card to fix rebooting issue. Replaced bipolar RAM at 3F to fix character issue. Tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:50:12 PM
Model: Ms Pac Man
Symptom: Dead

Board had a short on the +5v line and an attempted repair had been made.

Replaced the regulator current pass transistor/heatsink assembly to fix short. Replaced the CPU, CPU socket, 1 ROM socket, and the ribbon cable. Tested board.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:50:23 PM
Model: Ms Pac Man
Symptom: Dead

Jumpered 6 bad traces on a previously replaced socket and replaced the ribbon cable. Tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:50:32 PM
Model: Pac Man
Symptom: Garbled video

Board was modified with the 4-in-1 game single ROM mod and an NVRAM adapter for saving high scores.

The NVRAM adapter doesn't fit well with ceramic cased RAM chips under it. Stacked 18 pin sockets under the adapter and tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:50:42 PM
Model: Ms Pac Man
Symptom: Dead

Board would not boot. Voltage was sitting at 4.17 volts and the board started smelling hot. Removed the backwards installed Z80 Sync Bus Controller module and board would then come up at proper 5.0 volts. Replaced all 8 TTL ICs on the module, reinstalled it, and tested the game. Replaced the missing zip ties to hold the modules in place and replaced burnt traces on the edge connector with copper trace tape. Retested game.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:50:50 PM
Model: Ms Pac Man
Symptom: 4 small screens of garbage on monitor

Replaced bad 74LS161 at location 3R. Tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:51:01 PM
Model: Bosconian
Symptom: White screen

Replaced all of the 24/28/40/42 pin sockets on the board. Replaced bad PROM on the video board to fix white screen issue. Board worked but had intermittent graphics issues and no music. Replaced a PROM on the CPU board to fix music issue. Replaced 3 bad 74LS367 chips buffering the CPU board to the video board and 1 74LS138 on the CPU board which fixed the intermittent graphics issue but then the board had issues with text showing up as multicolored and with every other column being flipped. Replaced 3 more 74LS367 chips buffering the CPU board to the video board.

Each one of the bad LS367 were Fujitsu brand and had broken die connections as the graphic corruption symptoms would come and go if the chips were tapped. Replaced the remaining 2 Fujitsu 74LS367 chips for good measure and did a final test on the board.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:51:10 PM
Model: Pac Man
Symptom: Graphic Corruption on maze. Sparkles on screen during attract mode.

Replaced bad character ROM at location 5E and tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:51:19 PM
Model: Pac Man
Symptom: Nothing on screen

Board would occasionally flash "Memory OK" on the screen but other wise was blank.

Replaced 2 bad program ROMs and tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:51:30 PM
Model: Galaga
Symptom: Dead. Nothing on screen

Board had been previously worked on. All but one of the 24/28/40/42 pin sockets were replaced. Checked for bad solder joints and shorted solder joints. Found none.

Game had no clock signals. Crystal was oscillating but the clock was missing. Replaced bad 74LS368 at 5a. Clock signal was now making it to the divider but not out. Replaced bad 74107 at 5B. Board would power up but not run. If the board was reset manually it would boot and work. Replaced C44 and the power on reset circut was now working. Board would run but had no music. Replaced bad PROM at 1D. Tested. Replaced the socket on 6M to finish replacing all the sockets on the board. Installed all new resistor packs to replace the old ones that go intermittent and retested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:51:42 PM
Model: Galaga
Symptom: Dead. Garbage on screen.

Board had been previously worked on. New 24/28 pin sockets and resistor packs had been installed.

CPU board tested good by substitution. Board was not attempting to boot at all. Checked the 2k x 8bit SRAM IC, the main CPU's memory, for missing signals. Jumpered a bad trace going to pin 1 from a replaced resistor pack. Tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:51:51 PM
Model: Galaga
Symptom: No music or sound effects

The explosion sounds worked. Checked the digital parts of the sound circuitry and found that the /DO1 through 4 lines on the 7489 at 2A were stuck high. Replaced the bipolar RAM chip and tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:52:01 PM
Model: Pac Man
Symptom: Game plays but has flickering garbage through screen.

Pin 15 was broken off the VRAM Addresser module. Replaced the adapter socket on the bottom of the module and tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:52:11 PM
Model: Pac Man (96-in-1 kit installed)
Symptom: Dead

96-in-1 kit was tested by the seller of the kit and sent back to the board owner with a new ribbon cable, but board would still not work.

Checked the 2114 RAM chips and both daughter boards. Did a check of the bottom of the board for trace damage and found a solder smear between pin 3 of 6S and two traces next to it. Used liquid flux and a hot iron to remove the short. Tested board.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:52:21 PM
Model: Ms Pac Man
Symptom: Dead

Board had attempted repair damage.

Board was stuck in reset. Replaced bad IC at 5M to fix reset problem. Replaced the 4 factory PROMs with broken legs with 4 programmed EPROMs. Fixed a broken pin on the Z80 Sync Bus Controller module. Tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:52:34 PM
Model: Ms Pac Man
Symptom: Dead

Board had attempted repair damage.

Replaced the 4 factory PROMs with broken pins with 4 programmed EPROMs. Replaced 8 bad 2114 DRAMs and their sockets. Tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:52:45 PM
Model: Pac Man Plus
Symptom: Dead

Board had attempted repair damage.

Repaired gouged trace. The CPU module was bad. Installed a Z80 CPU, 4 program EPROMs, 2 character EPROMs, Color PROM, Video Output PROM, and a Ms Pac Man daughter board to convert game to Ms Pac Man at customer's request.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:52:59 PM
Model: NBA Hangtime
Symptom: RAM Errors

Board had physical damage. Straightened bent pins on U32 and removed 2 solder smears from the bottom of the board to fix RAM errors. Reprogrammed U112 to fix a ROM error. Tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:53:31 PM
Model: Ultimate Mortal Kombat 3
Symptom: RAM Errors

Board had physical damage.

Replaced a bent pin on the PLCC socket for U45. Tested board. Reprogrammed U3, U113, and U132 to fix ROM errors. Tested board.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:53:47 PM
Model: Galaga
Symptom: Parts board rebuild

Board had been worked on before and put into a box of parts boards by another tech. Two of the customs on the video board were in wrong sockets, one ROM was in the wrong socket, and the 06XX and 16K SRAM chips were missing.

Installed renew kit - all new sockets & resistor packs. Cleaned custom chip legs. Installed missing ICs. Repaired pins on the 02XX and the 07XX chips on the video board. Board would boot but would fail randomly on start up on different RAM chips. Replaced a bad 74LS138 at 1E on the video board to fix a random memory error on boot. Tested board.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:53:57 PM
Model: Galaga
Symptom: Parts board rebuild

Board had been worked on before and put into a box of parts boards by another tech. Four resistor packs were replaced with the wrong type and a 5th had been replaced with the bad, flat style of resistor pack that should not be used on these boards.

Installed renew kit - all new sockets & replaced all old style resistor packs. Cleaned custom chip legs. Repaired pins on 2x 08XX, 51XX, and the 54XX chips on the CPU board. Board would boot but would fail with a 4L RAM error. Replaced a bad 08XX IC on the CPU board and tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:54:07 PM
Model: Galaga
Symptom: Parts board rebuild

Board had been worked on before and put into a box of parts boards by another tech. Three caps had been replaced incorrectly.

Installed renew kit - all new sockets & replaced all old style resistor packs. Cleaned custom chip legs. Repaired 2 pins on one 08XX IC and replaced 3 incorrect caps - 2 radial and 1 axial that was physically too big. Removed tape from the edge connector and cleaned the residue. Tested board
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:54:20 PM
Model: Mortal Kombat 4, Revision 2
Symptom: Burnt components next to JAMMA edge conector

Replaced a bad 0 ohm surface mount resistor in the Video Ground circuit. Replaced a bad surface mount cap in the Sync Output and Blue Output circuits. Replaced a bad 33 ohm resistor in the Blue Output circuit. Board powered up but had no sync. Replaced a bad surface mount 7407 IC in the Sync Output circuit and tested the board.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:54:29 PM
Model: Mortal Kombat III
Symptom: Dead

Jumpered 1 burnt trace where a coil used to be. Replaced a surface mount coil at L54 in the power circuit for a 74ABT244. Reflowed the DMA Controller at U33 and the Orbit chip at U32. Board booted with WWF instead of MKIII. Replaced all ROMs and the security chip. Tested. Board had graphics corruption. Replaced chip at U45 and retested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:54:40 PM
Model: MKII
Symptom: Reboots at random

Reflowed the surface mount DMA Controller IC. Tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:54:49 PM
Model: WWF Wrestlemania
Symptom: Random reboots and garbage on screen

Reflowed the DMA Controller IC and fixed bent pins on a custom PLCC. Replaced bad U125. Cleaned battery contacts and tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:55:00 PM
Model: UMK3
Symptom: Lines under players. Fails self tests showing all Graphics ROMs bad.

Resoldered the CPU and 3 RAMs to fix lines under player issue. Address lines A0-A6 on the Graphics ROMs were not being actrivated during self test. Replaced a bad 74F373 and tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:55:09 PM
Model: Mortal Kombat 4
Symptom: No video sync

Replaced a dead SMT 74LS07 and a fried zero ohm SMT resistor in the video ground circuit. Tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:55:19 PM
Model: Mortal Kombat 4
Symptom: No video output

Replaced 3 fried 33 ohm SMT resistors to fix the video output. Replaced a dead SMT 74LS07, a 1K SMT resistor, and a fried zero ohm SMT resistor in the video ground circuit to fix the sync issue. Tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:55:28 PM
Model: NBA Max Hangtime
Symptom: Missing U36. No sound in game. 10 bongs during self test.

Replaced missing U36. Board would then boot but showed a ROM error. Reprogrammed U132 ROM. Board would boot but fail sound tests with 10 bongs. Replaced cracked SMT coil in the sound circuit. Tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:55:37 PM
Model: WWF Wrestlemania
Symptom: Bad U14 during self tests

Replaced IC U14. Tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:55:47 PM
Model: Ms Pac Man
Symptom: Dead

Cleaned the tarnished legs on 3 mask ROMs and corroded legs on 1 EPROM. Tested
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:55:57 PM
Model: Ms Pac Man
Symptom: Dead. Missing ribbon cable.

Board was part of a bulk buy and had a bootleg Ms Pac daughter board and no ROMs on row 6. Board was also poorly converted to run on DC power.

Removed several jumper wires and repaired a burnt pin on the edge connector. Installed ribbon cable and tested. Fixed broken pin on the sync buss controller chip. Board would still not boot. Replaced bad CPU and successfully tested.

Installed ROMs on row 6 and replaced the bootleg daughter board with an original. Since the bootleg board required no ROMs on row 6, kept that board as a troubleshooting tool for fixing Pac/Ms Pac/Pac Plus boardsets to quickly rule out ROM issues.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:56:09 PM
Model: Ms Pac Man
Symptom: Dead

Board would boot if tapped "just right". Replaced sockets on the 74LS259 at 8K, the CPU, and the Z80 Sync Buss Controller. Board booted and worked, but had very thin horizontal lines bridging some text. Replaced the PROM at 4A and tested.

Replaced a bad 2200uf cap and an incorrect 330uf cap where someone used a radial instead of axial. Tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:56:18 PM
Model: Pac Man
Symptom: Dead

Fixed bent pin 20 on CPU, replaced bad socket on Z80 Sync Buss Controller, and patched one bad trace. Tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:56:27 PM
Model: Pac Man
Symptom: Dead

Replaced bad socket on Z80 Sync Buss Controller and replaced the Ms Pac ROMs on row 5 with Pac Man ROMs. Tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:56:38 PM
Model: Ms Pac Man
Symptom: Dead

Replaced bad socket on ROM at 6E and the socket for the Z80 Sync Buss Controller. Replaced missing socket on the pins of the Z80 Sync Buss Controller card. Board would boot but had glitches in background graphics and missing characters. Replaced bad socket on the ROM at 5F to fix glitching and replaced a bad 74LS20 at 3E to fix the missing characters. Tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:56:49 PM
Model: Pac Man
Symptom: Dead

Replaced bad CPU, ROM 6E, and fixed a broken pin on the EPROM in 6J. Jumpered a cut trace on 8C pin 11 to undo a mod someone had performed on the board. Replaced bad Mask ROMs at 5E and 5F. Board played but had horizontal lines across screen. Replaced bad RAM at 1C and tested. Repaired burnt edge connector and restested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:56:57 PM
Model: Pac Man
Symptom: Dead

CPU was dead. Checked /RESET and it was missing. Replaced bad 74LS161 at 9C. Board would try to boot but fail and the data bus would lock. Replaced bad 74LS245 at 4H. Tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:57:06 PM
Model: Galaga
Symptom: Dead

Board had attempted repair damage. Board was part of a pile of parts boards to be resurrected and had already had the 40, 42, and 28 pin sockets replaced on the CPU board.

Cleaned the excess solder from the edge connector. The audio amp chip had severe heat damage. Replaced 4 incorrect radial capacitors with proper axial types. Removed solder short from the only correct axial type installed (C20) that grounded out the output of the audio amp chip. Removed the heat damaged audio amp chip, rebuilt missing ground trace with copper foil tape, installed replacement amp, and jumpered 2 missing signal traces to it.

Removed solder shorts from the 06xx and one of the 08xx chips. Boardset was still dead. Examined the custom ICs on the CPU board and discovered the 06xx was missing the ground pin. Replaced the damaged socket on the 06xx and attached a pin from a donor chip. Tested. Boardset still had no video but would now play blind.

Examined the video board. The 05XX chip had 5 broken pins. Replaced the old style resistor packs on the video board and replaced all the 24/28 pin sockets. Cleaned the legs on the customs. Replaced a wire patch on the 07XX chip with a leg from a donor chip. Repaired the 5 damaged pins on the 05XX custom chip with legs off a donor chip. Tested board.

NOTE: The PROM at 5N outputs the video. The enable line (pin 15) for it is controlled by the 05XX. The missing power pin caused the 05XX to be dead and not enable video output.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:57:19 PM
Model: Ms Pac Man
Symptom: Dead

Cleaned corroded pins on U6/U7 ROMs and replaced the ribbon cable socket on the daughter board. Game would try to boot and crash. Replaced the Z80 Sync Buss controller and the VRAM Addresser sockets. Board booted but immediately started a game and move to the left. The screen would shift colors to all white and the eyes for the ghosts would not line up with the character sprites. Noticed that if the data bus pins were probed with the logic probe that Ms Pac would move on the screen according to the DB pin that was probed corresponding to the 74LS367 outputs for the control inputs, but the controls themselves were non-responsive.

Replaced 74LS138 at 7J to fix input problem. It wasn't toggling the /IN0 and /IN1 enable lines on the 74LS367 chips buffering the inputs. Replaced the PROM at 4A to fix the colors shifting. Replaced the color RAM at 2A to fix the problems with the eyes on the ghosts and horizontal lines on the screen.

Repaired a burnt trace on the edge connector, replaced a physically damaged resistor at R5, and retested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:57:28 PM
Model: Ms Pac Man
Symptom: Dead

Replaced 4 corroded ROMs and sockets on row 6. Board had scrolling garbage on screen. Replaced bad 74LS161 chips at 2S, 3R, 1E and 2E. Replaced bad CPU and ribbon cable. Board booted but had no sound. Replaced sound PROM at 1M and tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:57:38 PM
Model: Ms Pac Man
Symptom: No characters on screen. No sound.

Board had been modified for a single ROM hack.

Characters were missing on screen. Chips in the motion RAM circuit checked good. The text at the top of the screen for Player 1, High Score and Player 2 were doubled. The "free play" text and the player scores were missing. Replaced bad 74LS157 in the center of the VRAM addresser to restore characters and fix the text issues. Pin 12 was stuck.

Replaced IC 3L to fix missing sound problem. Board would boot and play, but had sparkles in ghosts and player sprites. Replaced bad ROM at 5F and tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:57:47 PM
Model: Ms Pac Man
Symptom: Garbage on screen

Board played but had corrupt graphics. Replaced shorted 74LS194 at 5B and 5C and a shorted 74LS157 at 5A. Tested
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:57:56 PM
Model: Ms Pac Man
Symptom: Randomly dies with black screen

Could replicate issue by tapping or thumping board. Replaced single wipe socket at 3R with a double wipe and cleaned the tarnished pins on the 74LS161 IC. Tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:58:05 PM
Model: Ms Pac Man
Symptom: Dead. Attempted repair damage

Board had a ham fisted repair attempt done with 3 sockets and multiple pulled traces on the ROMs on row 6.

Trimmed back the traces pulled from the board, installed 3 sockets, and patched 13 damaged traces. Installed two ROMs supplied with the board, programmed a replacement for the missing ROM at 6J, and installed it. Board would try to boot but fail. Replaced 4 bad RAMs and tested. Board would run but would reboot by itself. Replaced bad ribbon cable between the board and the daughterboard and retested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:58:16 PM
Model: Pac Man
Symptom: Dead. Attempted repair damage

Board had a very badly done chip replacement attempt. IC 8E was removed, a machine pin socket installed, and a new IC in the socket, but the pads were badly damaged. IC 4A was missing

Board had very rusted ROM chips on rows 5 and 6. Replaced the ROMs with programmed 2532 EPROMs and installed a bipolar PROM at IC 4A. Board would attempt to boot but had garbage on screen. Data bus signal DB4 was malformed.  Replaced bad bipolar RAM at 3H. Board would attempt to boot further, but still would not. Replaced the 74LS245 at 4H which cleaned up the data bus signals but it still would not boot fully.

Tested the 2114 RAM and replaced 1 bad one. Removed the poorly installed 74LS367 at 8E and the board would boot further but the screen was still scrambled. Replaced bad NVC284 IC with a V-RAM Addresser daughter board to unscramble the screen. Found a solder short on data bus signal DB2 on the poorly installed IC at 8E. Removed the solder short and the game would then boot, but had incorrect ghost names, no sound, ghosts with wrong colors, and ghosts that moved poorly.

Replaced the 74LS75 at 3D to fix the colors. Replaced the bipolar RAM at 3F to fix the ghost movements. Replaced the bipolar RAMs at 2K and 2L to restore the sound. Removed the poorly installed socket at 8E and found the trace for the control signal for IC 8D was broken and shorted to pin 2 of 8E. Removed the short, soldered the IC at 8E directly to the board, and patched the control signal trace for IC 8D to fix the incorrect ghost names.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:58:26 PM
Model: Ms Pac Man
Symptom: Dead. Missing parts. Attempted repair damage

Pads were damaged on the ROM sockets on row 6 and there was one shorted solder connection between pins 1 and 2 of the ROM at 6E. Removed the 4 non-original sockets on row 6 to discover many damaged traces. Trimmed the traces that were sticking up off the board, installed new sockets, and patched 8 traces. Replaced a bad 74LS259 at 8K, installed a missing Sync Bus Controller, V-RAM Addresser, and ROMs on row 6. Replaced the hardened ribbon cable to the daughterboard, and tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:58:36 PM
Model: Ms Pac Man
Symptom: Crashing/Rebooting

Board would crash and reboot when using the Ms Pac Man daughter card, but would play fine as Pac Man. Daughter card and ribbon cable tested fine on another board. When using the logic probe with a finger touching the tip (adding extra capacitance) and probing address line A8 input on pin 6 of the 74LS367 at 6R, the game would boot an run perfectly as Ms Pac Man. Replaced bad ROM at location 6H and tested.

The ROM passes self tests, would run fine without the Ms Pac daughter board added in, but had a bad gate on the input pin for address line A8 which caused problems when running at speed with the extra length of ribbon cable and the added chips on the daughter board.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:58:45 PM
Model: Galaxian
Symptom: RAM Error

Replaced bad RAM at 4F. Board would play, but the player's missile was represented by a stripe crossing the whole screen and during game play the game lost partial colors and would look like it had a yellow hue. Enemy shells were missing from screen. Found the /MLD and /SLD signals were incorrect and HBLANK was missing. Replaced bad 74LS74 at 3D and tested game. Replaced all electrolytic caps except the 2 large filters and retested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:58:56 PM
Model: Ms Pac
Symptom: No sync

Replaced bad 74LS161 at 2S. Repaired damaged edge connector power connection with copper tape. Tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:59:04 PM
Model: Ms Pac Man
Symptom: Dead. Garbage on screen

Cleaned and reseated RAM at 4N. Board would play but had stripes through characters. Cleaned and reseated ROM at 5F. Tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:59:15 PM
Model: Super Pac Man
Symptom: Static on audio output. Amplifier chip gets very hot.

Recapped the board and static was still present. At loud volumes the audio would have a repetitive thump thump sound. Replaced 2 missing capacitors on the audio amplifier's output to fix the amplifier chip's self oscillation problem. Tested board.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:59:23 PM
Model: Pac Man
Symptom: Dead

Reinstalled CPU with the correct orientation to pin 1. Cleaned the MASK ROMs and the NVC285 custom IC legs. Set the dip switches, installed zip ties on the VRAM Addresser card, and tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:59:32 PM
Model: Ms Pac Man
Symptom: Constantly reboots

Board was stuck in watchdog. Replaced bad 74LS138 and board would still reboot, but was rebooting because of a data bus problem instead of a watchdog reset. Data Bus line DB5 wasn't working correctly. Replaced 2 shorted capacitors on the control inputs and 1 shorted capacitor next to the ROM sockets on row 6. Replaced 1 bad 7489 bipolar RAM on the board and 2 74LS374 and 1 74LS244 on the Sync Bus Controller board to finish the repair.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:59:41 PM
Model: Pac Man
Symptom: Dead

Board had no reset signal. Replaced bad 74LS74 at 5M and a 74LS161 at 9C. Tested
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 08:59:50 PM
Model: Pac Man
Symptom: All 5s on the screen

Replaced all 6 RAM sockets at customer request. Replaced bad ROM at 6E. Tested. Board played but had odd pitches to the music. Replaced bad PROM at 1M and tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 09:00:05 PM
Model: Pac Man
Symptom: No vertical sync

Replaced bad 74LS161 at 2S. Tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 09:01:23 PM
Model: Galaga
Symptom: Missing colors on output. Board had terrible attempted repair damage.

CPU board was a converted Bosconian and had the extra chips cut off and pins left behind. It also had been repaired in the past with all 24/28/40/42 pin sockets replaced. Cleaned up the extra pins from the cut chips and checked the board.

The interconnect cable had a burned wire from a previous short circuit and was replaced.

Video board had all the 2147 RAMs removed with many lifted pads. 2148 RAMs were installed and 3 74xx logic chips were replaced and they were all socketed using 8 pin sockets. (!?!?!?!) Cleaned up the poor solder from where the 2147s were pulled. Removed the 8 pin sockets, cleaned up the solder pads, and installed correct sockets. Installed a missing 470uf capacitor and replaced the 74LS365 at 6A. Patched a bad trace on pin 1 of the 2148 and replaced a bad PROM to fix the color issues. Replaced the 24 and 28 pin sockets, old style resistor packs, installed 2 missing PCB standoffs, and tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 09:01:40 PM
Model: Bosconian
Symptom: Crashes upon starting a game. Board had massive attempted repair damage to the CPU board.

Board had multple incorrect resistor packs: ten pin packs instead of nine, 6 pin packs in stead of 5 and the extra legs cut off and floating above the board. One 2200 ohm resistor pack had a bad section and a 1k ohm resistor soldered across its pins on the bottom side of the board(!?!?!?). Replaced the remaining, old style resistor packs. Replaced 2 never replaced ROM sockets, 3 never replaced CPU sockets, and 1 incorrect (cut down 48 pin) 42 pin socket on the CPU board. Reseated one of the 8xx chips that had a bent pin and fixed a couple of bad traces that were damaged when someone previously removed one of the 8xx chips (affecting a data line on the 3rd CPU) and one of the resistor packs by the edge connector.

Replaced the 24/28 pin sockets and all the old style resistor packs on the video board. Tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 09:01:50 PM
Model: Pac Man
Symptom: Dead

Board had previous work done to it. The 74LS74 and 74LS368 ICs were poorly repaired for broken pins.

Replaced the 74LS74 at 8C and 74LS368 8B and their sockets. Replaced the 74LS161 at 3S. Replaced the socket for the VRAM Addresser and replaced the broken socket on the bottom of the daughter board. Replaced the 4 corroded mask ROMs with EPROMs. Tested. Zip tied the 2 daughter boards to the main board. Re-tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 09:01:58 PM
Model: Super Pac Man
Symptom: Missing sound

Replaced missing cap at C26. Sound worked but was distorted. Replaced bad 15xx custom IC at 3N. Tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 09:02:08 PM
Model: Super Pac Man
Symptom: RAM Error 1

Replaced bad RAM on video board and 2 bad RAMs on the CPU board. Tested. Audio was garbled. Replaced bad PROM at 3M and retested.

NOTE: Super Pac Man will stop when it finds a RAM error. Replace the bad RAM and continue to reboot/repair until all RAM errors are gone. ROM tests will probably act the same way.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 09:02:24 PM
Model: Bosconian
Symptom: Dead

Replaced all 24/28/40/42 pin sockets and old style resistor packs on CPU and Video board. Replaced missing SRAM on CPU board. Recapped audio section. Tested. Board had graphic corruption on text and graphics. Replaced bad PROM at 7H and tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 09:02:35 PM
Model: Galaga
Symptom: Crashes/reboots

Replaced all 24/28/40/42 pin sockets on the CPU and video boards. Replaced all the old style resistor packs on the CPU board and video board. Repaired broken pins on the 54XX chip and the 04XX chip. Tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 09:02:49 PM
Model: Galaga
Symptom: Dead. Garbage on screen

Replaced all 24/28/40/42 pin sockets on the CPU and video boards. Replaced all the old style resistor packs on the video board. Installed new interconnect cable and replaced a bad 74LS245 on the video board. Repaired 2 broken traces on the video board. Tested. Recapped the audio section and replaced the 2 470uf power filter caps. Retested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 09:02:58 PM
Model: Galaga
Symptom: Missing player/text graphics

Fixed 3 broken pins on the 54xx, 1 ea. on 2 of the 8xx chips. 1 trace on the 51xx chip where the socket was replaced by 2 old single wipe cut down sockets. The CPU sockets were dual wipe and OK. Replaced the 28 and 42 pin sockets and all the old style resistor packs. It booted with a ROM 03 error. Pulled the ROM at 3L out of the socket and fixed a bent pin. Replaced the 24 pin sockets to finish the CPU board.

Replaced the 24/28 pin sockets and the old style resistor packs on the video board. Fixed a broken pin on the 00xx and 05xx chips. Fixed a bad trace on the 1K resistor pack. Tested the boardset and found the sound for the player ship being captured by the enemy was incorrect. Replaced mismatched sound ROM at 3E and retested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 09:03:06 PM
Model: Pac Man
Symptom: Graphic Corruption

Socket on 5F was previously replaced.

Found 3 damaged traces on 5F. Jumpered traces and tested. Graphics were better but still slightly corrupt. Removed socket from 5F, removed damaged trace causing short, and reinstalled socket. Tested. Sound was corrupt. Replaced bad 74LS86 at 4F and retested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 09:03:21 PM
Model: Pac Man
Symptom: Dead

Fixed 3 broken solder joints on the Sync Buss Controller board. Game would boot the Six Pac mod, but had graphic corruption. Replaced bad CPU and retested. The upper address lines were not working correctly and bank switching was failing.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 09:03:30 PM
Model: Mortal Kombat
Symptom: Low audio

Cleaned under a leaky 220uf cap on the audio board, recapped the audio board, and tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 09:03:38 PM
Model: Mortal Kombat
Symptom: Crackling and low audio

Cleaned under the leaking 100uf and 220uf caps on the audio board, recapped the audio board, and tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 09:03:50 PM
Model: Mortal Kombat
Symptom: Low audio until board warms up

Cleaned under the leaking 220uf cap on the audio board, recapped the audio board, and tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 09:03:58 PM
Model: Mortal Kombat
Symptom: Low and crackling audio

Cleaned under 3 220uf, 1 2200uf, and 5 100uf caps that were leaking on the audio board. Recapped the audio board and tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 09:04:07 PM
Model: Pac Man
Symptom: Burnt edge connector

Repaired the edge connector with copper tape and tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 09:04:16 PM
Model: Ms Pac Man
Symptom: Burnt edge connector

Repaired edge connector with copper trace tape. Tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 09:04:26 PM
Model: Ms. Pac Man
Symptom: Dead

Replaced missing Z80 Sync Buss Controller module and the 28 pin socket in mounts to. Replaced a bad 74LS283 in the sound circuit. Tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 09:04:36 PM
Model: Carnevil
Symptom: No sync.

Replaced bad 7407 IC and tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 09:04:47 PM
Model: Rampage World Tour
Symptom: Random errors that change with board flexing

Reflowed U1, U13, U24, U25, U32, U33, U36, U37, U38, U39, U65, and U66. Tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 09:05:01 PM
Model: NBA Hangtime
Symptom: Bad background noise in audio

Replaced bad TL092 OpAmp at U92. Tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 09:05:10 PM
Model: Galaga
Symptom: Freezes, randomly coins up by itself.

Board has had repair attempts before. All the 2147 RAMs were pulled and 2x 2148 RAMs installed by another tech.

Replaced all the 24, 28, 40, and 42 pin sockets. Replaced all the old style resistor packs. Found a 2.2K pack that had a broken pin causing the freezes and a 5 pin 1K pack with 2 broken pins causing color issues that the previous tech replaced the RAM for. Recapped the board. Repaired bad pin on the 52xx causing the coinup issues. Repaired a bad pin on the 04XX chip. Tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 09:05:22 PM
Model: Galaga
Symptom: Freezes and resets on its own

Board had been worked on in the past by another tech.

Replaced the 24, 28, and 40 pin sockets on the CPU board. The resistor packs were of the proper type and the remaining sockets were machine pin and did not need replacing. Found all of the 24 pin sockets on the EPROMs were incorrectly installed, standing off the board about 1/16", and two of them had pins that had broken off under the socket causing the bad behavior. Tested board.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 09:05:41 PM
Model: Rampage World Tour
Symptom: Graphical Corruption during game

Board had stripes and bleeding colors throughout playfield and outside of the playfield around the screen borders.

Replaced U32, U10, U11, U14, U15, U38, and U75. Tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 09:05:49 PM
Model: Mortal Kombat 4
Symptom: No sync, burned component.

Rebuilt burnt traces and pads, replaced a burnt 0 ohm resistor in the video ground circuit, and replaced a missing surface mount capacitor. Tested board. Replaced bad surface mount 7407 IC to fix missing sync. Retested to find sync fixed but some buttons not working. Cleaned JAMMA edge connector and tested board again.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 09:06:39 PM
Model: Mortal Kombat
Symptom: Will not play a game

Will run through attract mode and coin up. When starting a game it immediately goes to Game Over and ends.

Reflowed the custom DMA controller IC at UE13. Tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2014, 09:09:38 PM
Model: Ms Pac Man
Symptom: Dead

Replaced bad CPU socket and cleaned corroded pins on the CPU. Board would play but had graphical corruption and missing player/ghosts. Patched a bad trace on the VRAM Addresser module to fix graphical corruption. The missing player/ghosts issue was much harder to track down. Replaced a bad IC at 5N. Pin 4 input was bad and the output signal of the gate on pin 6 was only the input from pin 5.

Zip tied the daughterboards in place and ran extended burn in tests on the boardset.
Title: Re: Midway Games
Post by: channelmaniac on July 01, 2014, 09:39:07 PM
Model: Galaga
Symptom: "Please rebuild"

Missing ribbon cable and had attempted repairs done to it.

Replaced all the 24/28/40/42 pin sockets. Inspected the work done to the boards and reflowed all the previously replaced resistor packs and capacitors to fix cold solder joints. Checked all the previously replaced ICs and fixed solder shorts on a 74LS245 on the video board. Patched a damaged trace to a previously replaced DIP switch.

Replaced missing ribbon cable and a broken standoff. Tested.
Title: Re: Midway Games
Post by: channelmaniac on July 27, 2014, 12:18:40 PM
Model: Galaxian
Symptom: Reboots at random

Cleaned the legs of the mask ROMs and replaced bad ROM at location Y on the daughterboard. Tested.
Title: Re: Midway Games
Post by: channelmaniac on August 02, 2014, 10:07:08 PM
Model: Galaga
Symptom: Stuck in reboot loop

If board would boot it would coin up at random. Replaced bad 06XX custom chip on CPU board and tested.
Title: Re: Midway Games
Post by: channelmaniac on August 04, 2014, 08:18:53 PM
Model: Galaga
Symptom: Dead. Reportedly smoked on power up.

CPU board had attempted repair damage and corrosion damage from some type of spray cleaner. The video board was mismatched to the CPU boardset and was an older board. The 8XX chip at 2J as installed at 2L and a 07XX chip was installed at 2J. The board was missing the 06XX chip. Corrosion damaged DIP switches would not make contact when set to on.

One of the tantalum capacitors for dampening the audio amp chip had burned up. Replaced both tantalum caps, cleaned the top board of solvent, replaced all the 24/28/40/42 pin sockets on the CPU board and video board. Patched a damage trace missed by previous tech. Replaced all the old style resistor packs on the video board and the corroded ones on the CPU board. Replaced corrosion damaged ribbon cable.

Board would not boot. Erased and reprogrammed the corrupt EPROMS at 3N, 3M, 3L, and 3K. Board would attempt to boot but had memory errors. Replaced all 6 2114 RAMs and the 74SL245 ICs at 2F and 2H along with the 6116 SRAM on the video board as all the RAM tested bad in the BK 560A. Replaced bad 74LS138 at 1E on the video board.

Now board would boot but had corrupt graphics. Replaced bad 74LS161 at 5E on the video board to fix the graphics issue. Board suddenly was stuck in a reboot loop. Replaced bad Fujitsu 74LS367 ICs at 1E, 1F, 1H, 1J, 1K, and 1L on the CPU board. Board would now boot but had no audio. Recapped the board and replaced bad MB3730 audio amp chip.

Board now had audio but audio was playing 2x normal speed and board would crash when testing the NMI line on the CPU at 4E. Replaced bad 74LS393 at 6A and retested. Replaced open DIP switches at 6J and 6K on the video board, installed new standoffs, and burned board in for a few hours.
Title: Re: Midway Games
Post by: channelmaniac on August 12, 2014, 05:54:20 PM
Model: Mortal Kombat 4
Symptom: No sound or sync

Replaced bad 7407 IC to fix sync. Replaced blown AD1851 DAC and TL084 Op Amp to fix audio issue. Reprogrammed the IC10/IC11 ROMs as one was for Rev 3.0 and the other 2.1.
Title: Re: Midway Games
Post by: channelmaniac on August 16, 2014, 12:38:04 PM
Model: Ms. Pac Man
Symptom: Hum in audio

Board had attempted repair damage.

Board arrived dead due to improper packing. Replaced damaged ribbon cable, straightened bent pins on the Z80 Sync Bus Controller card and reinstalled it. Replaced bad rectifier diodes, replaced 3 backwards capacitors in the audio section, replaced 3 other axial caps, and tested.

Board lost vertical sync while on the bench. Replaced bad 74LS161 at 2S to fix a missing 64V signal. Ran extended burn-in tests.
Title: Re: Midway Games
Post by: channelmaniac on August 23, 2014, 08:50:40 AM
Model: Pac Man
Symptom: Moving characters are corrupted

Moving characters on screen were in the wrong position, moving incorrectly, and would come and go on screen. Replaced cracked 1K resistor pack and tested.
Title: Re: Midway Games
Post by: channelmaniac on September 01, 2014, 03:01:55 PM
Model: Galaga
Symptom: ROM Error and Graphics Issues

Installed new resistor packs and 24/28/40/42 pin sockets. Cleaned the custom ICs. Replaced broken PC board standoff and tested.
Title: Re: Midway Games
Post by: channelmaniac on September 13, 2014, 07:16:51 PM
Model: Galaga
Symptom: Garbage on screen

Board had rebuilding attempts made.

Removed 2 EPROMs, the 3 08xx chips, and the 06xx chips, cleaned solder splashes from under the sockets, then replaced them. Removed and reinstalled a backwards resistor pack on the video board. Resoldered all the 24/28/40 pin sockets. Replaced a broken 42 pin socket.

Board booted and worked, but had tinny sound. Recapped board and retested.
Title: Re: Midway Games
Post by: channelmaniac on September 13, 2014, 07:44:34 PM
Model: Pac Man
Symptom: No sound. Only clicks.

Replaced bad 74LS174 at location 1L. Tested.
Title: Re: Midway Games
Post by: channelmaniac on September 20, 2014, 03:07:50 PM
Model: Galaga
Symtpom: Dead. Garbage on screen

Replaced all the 24/28/40/42 pin sockets. Cleaned the pins on the customs and repaired a pin on one 08xx. Replaced the electrolytic caps on the boardset and tested.
Title: Re: Midway Games
Post by: channelmaniac on September 20, 2014, 06:57:44 PM
Model: Galaga
Symptom: Dead, garbage on screen

Board had previous repairs. CPU board was populated with 24/28/40/42 pin machine pin sockets already.

Cleaned copious amounts of hot glue off of the CPU board and recapped it. Replaced the 1000 ohm and 2200 ohm resistor packs on the video board. Cleaned all the hot glue off the Video board and installed new 24/28 pin sockets on it. Replaced 2 broken .1uf ceramic capacitors and replaced the old 470uf electrolytic capacitor. Cleaned the custom ICs, replaced the 00xx and 07xx ICs as they had multiple broken legs when pulled from their old sockets.

Tested board.
Title: Re: Midway Games
Post by: channelmaniac on September 20, 2014, 10:03:12 PM
Model: Galaga
Symptom: Corrupt Graphics

Board played but the characters were split in two with every other vertical line of the characters separated by about 1/2 of a screen. Replaced bad 74LS161 at 5D. Tested.
Title: Re: Midway Games
Post by: channelmaniac on September 22, 2014, 09:07:44 PM
Model: Galaga
Symptom: Garbage on screen

Recapped the boardset and replaced all the 24/28/40/42 pin sockets. Replaced the old style resistor packs on the CPU and video boards, cleaned the custom ICs, and tested.
Title: Re: Midway Games
Post by: channelmaniac on October 03, 2014, 07:40:43 PM
Model: Galaga
Symptom: Crashes and reboots

Replaced the 2200 and 1000 ohm resistor packs on the video board with epoxy encapsulated types. Replaced all 24, 28, 40, and 42 pin sockets with dual wipe sockets. Cleaned pins on the custom ICs and recapped board. Tested.
Title: Re: Midway Games
Post by: channelmaniac on October 19, 2014, 03:26:34 PM
Model: Galaga
Symptom: Colors wrong and starfield too fast

CPU board was already rebuilt. Replaced 24/28 pin sockets and old style resistor packs on the video board. Cleaned the custom ICs and tested. Starfield problem was now gone, but the color RAM stayed the same. Replaced RAM at 6K to fix color issue.
Title: Re: Midway Games
Post by: channelmaniac on October 19, 2014, 06:23:53 PM
Model: Galaga
Symptom: RAM Error

Board had attempted repair damage.

Replaced all the 24/28/40/42 pin sockets and old style resistor packs on the CPU board and video board. Replaced the 6 RAM sockets to fix the RAM error. Replaced a bad PROM at 1D on CPU board to fix incorrect sound effects.

Title: Re: Midway Games
Post by: channelmaniac on October 22, 2014, 09:36:23 PM
Model: Ms. Pac Man
Symptom: Dead. Garbage on screen.

Ribbon cable was physically damaged and had wire extensions soldered to the bottom of the board. Removed the extensions, replaced the ribbon cable, and tested.
Title: Re: Midway Games
Post by: channelmaniac on November 28, 2014, 10:22:22 PM
Model: Mortal Kombat II
Symptom: Will not play game

Coin up and try to play the game and it will only display "Game Over" and go back to attract mode.

Reflowed custom DMA Controller IC at UE13 and tested.
Title: Re: Midway Games
Post by: channelmaniac on November 28, 2014, 10:24:09 PM
Model: Mortal Kombat II
Symptom: ROM Error on sound board

Board failed diagnostics with 2 bong sounds indicating a bad ROM. ROM checksum was good. Patched gouged trace next to IC U24 and tested.
Title: Re: Midway Games
Post by: channelmaniac on December 01, 2014, 10:20:57 PM
Model: Pac Man
Symptom: Dead. Colored stripes on an unstable screen.

Replaced broken socket attached to the Sync Buss Controller daughterboard. Replaced the single wipe socket on the game board with a double wipe socket. Board would boot but had the aforementioned issues.

6MHz clock signal from the 74LS368 was unstable and causing strange symptoms including horizontal colored stripes across screen, screen jittering, and random rebooting. If the logic probe was placed on pin 11 of the 74LS161 at 2E the screen would become more stable. Replaced 74LS161 at 2E and the color RAM at 2D. Removed short under the IC at 2E between pin 9 and the 6MHz clock signal. Tested. Replaced Pac Plus PROMs at 4A and 7F with Pac Man PROMs. Installed zip ties on the 2 daughterboards and retested.
Title: Re: Midway Games
Post by: channelmaniac on December 03, 2014, 07:07:50 PM
Model: Pac Man
Symptom: Will not boot into game. Board had a speed-up puck installed.

Removed puck. Resoldered cut leg on 8C, replaced bad ROM at 6F, and tested.
Title: Re: Midway Games
Post by: channelmaniac on December 03, 2014, 09:32:57 PM
Model: Ms. Pac Man
Symptom: Dead. Missing ROM and daughterboard cable.

Repaired multiple burnt edge connector contacts. Replaced missing cable and missing ROM at 6F. Board would not boot. Replaced bad IC sockets at 6E, 6F, 6H, and 6J. Removed multiple solder smear shorts from bottom of board. Board would play but had bad sound. Replaced PROM at 1M and tested.
Title: Re: Midway Games
Post by: channelmaniac on December 04, 2014, 09:39:11 PM
Model: Pac Man
Symptom: Dead. One ROM socket missing from the board.

Removed the individual pins from the missing socket and installed a new one. Erased the "Ms. Pac Man II" EPROMs and reprogrammed them with Pac Man at customer's request. Tested.
Title: Re: Midway Games
Post by: channelmaniac on December 30, 2014, 06:13:05 PM
Model: Mortal Kombat II
Symptom: Dead

Fixed bent pins on the ROM sockets on the bottom of the board. Fixed a bent power pin on UJ12 (Program ROM) and tested.
Title: Re: Midway Games
Post by: channelmaniac on January 04, 2015, 05:34:31 PM
Model: Mortal Kombat 2
Symptom: Dead

Replaced missing filter choke coil in +5v line and tested.
Title: Re: Midway Games
Post by: channelmaniac on January 04, 2015, 05:36:51 PM
Model: Mortal Kombat II
Symptom: Graphic corruption and reboot loop.

Board was a 4Mb ROM version and was missing daughterboard. Converted board to the single 8Mb revision using chips from a parts board and tested.

This conversion involves moving 4 jumpers between the program ROMs and graphics ROMs to activate address line A19, replacing the graphics ROMs, and replacing one PAL.
Title: Re: Midway Games
Post by: channelmaniac on January 04, 2015, 05:37:58 PM
Model: NBA Hangtime
Symptom: Dead

Replaced corroded battery holder and installed battery. Tested.

The boards in this series (including MK3/UMK3 and Rampage World Tour) require a good backup battery or they will appear to be dead.
Title: Re: Midway Games
Post by: channelmaniac on January 04, 2015, 05:39:56 PM
Model: Mortal Kombat 3
Symptom: Graphics corruption and ROM errors.

Board had physical damage.

Replaced several smashed SMT components: 1 capacitor, 1 coil, 1 74ABT244, and 1 74F244 IC. Patched one gouged trace on the bottom of the board. Programmed a replacement ROM for missing U129 and a replacement ROM for a bad U116. Tested.
Title: Re: Midway Games
Post by: channelmaniac on January 08, 2015, 03:36:11 PM
Model: NFL Blitz
Symptom: No video

Board would play blind and was sending a proper sync signal to the monitor.

Replaced three open surface mount resistors in the video output circuit and tested.
Title: Re: Midway Games
Post by: channelmaniac on February 07, 2015, 07:07:46 PM
Model: Ms Pac Man
Symptom: Random reboots and bad sound

Replaced the 2200uf cap in the audio circuit that had very high ESR readings. Replaced ribbon cable and 2 40-pin sockets on the daughterboard to fix reboot issues. Tested.
Title: Re: Midway Games
Post by: channelmaniac on April 07, 2015, 08:01:59 PM
Model: NBA Hangtime
Symptom: Every ROM bad on board. Missing sounds.

Resoldered the custom DMA Controller IC and tested.
Title: Re: Midway Games
Post by: channelmaniac on July 28, 2015, 04:37:13 PM
Model: Pac Man
Symptom: Dead

Replaced bad CPU and tested. Installed missing zip ties on daughterboards and tested.
Title: Re: Midway Games
Post by: channelmaniac on July 28, 2015, 04:37:55 PM
Model: Ms. Pac Man
Symptom: Dead

Replaced bad CPU and tested. Installed missing zip ties on daughterboards and retested.
Title: Re: Midway Games
Post by: channelmaniac on July 29, 2015, 08:38:13 PM
Model: Ms. Pac Man
Symptom: Dead. Stuck in reset. Extremely faint image on screen.

Replaced Sync Buss Controller IC socket and CPU socket. Interrupts and data lines were all going crazy. Broke out the Fluke 9010a and notice that three of the Program ROMs read properly. Cleaned the pins on the ROM at 6E and then it read properly. Board failed all RAM tests. The RAM reads would return random data at times and the control signals to the RAMs weren't quite right.

Replaced 74LS161 at 3R and the board booted. The 1H, 2H, and 4H signals were not dividing properly which threw off the control signal timing to the 2114 RAMs. Replaced the video output PROM at 7F with the proper PROM to restore video output. Someone had put a sound PROM from location 3M into that socket and its open collector outputs (not to mention different programming) wouldn't work properly in that circuit.
Title: Re: Midway Games
Post by: channelmaniac on August 01, 2015, 04:10:32 PM
Model: Galaga
Symptom: Dead.

Board had attempted repairs.

Replaced all the 24/28/40/42 pin sockets and old style resistor packs on the CPU board and video board. Replaced the 07xx and 00xx customs on the video board as they had multiple missing legs.

Tested and burned board in for several hours
Title: Re: Midway Games
Post by: channelmaniac on August 13, 2015, 07:57:09 PM
Model: Ms Pac Man
Symptom: Dead. Stuck in reboot with garbled characters on screen.

Board had attempted repairs done to it.

Looked board over and saw where the IC at 3H was replaced poorly. Fixed a solder short on one of the data lines and replaced the socket of 5F to fix the garbled characters. Board was still stuck in watchdog reboot.

Broke out the Fluke 9010A and the Z80 pod and discovered the ROM checks failed with random checksums. Cleaned the pins on the ROMs and they still but had steady, incorrect checksums. Fixed broken trace for data line D6 between the CPU and the Z80 Sync Buss Controller module. Tested board.

Replaced radial caps at C2, C5, and C29 with proper axial caps and retested.

The moral here is if you're repairing a board and it gets worse while you are repairing it then STOP and check your work. If the person who previously worked on this board had done this they would've seen the whisker short on the 7489 chip they replaced. Fixing that would've been easier than them replacing the CPU, Z80 Sync Buss Controller, and VRAM Addresser sockets with machine pin socket strips. When they did that they damaged a trace on the data buss further damaging the board.
Title: Re: Midway Games
Post by: channelmaniac on August 13, 2015, 07:59:27 PM
Model: Pac Man
Symptom: Missing parts.

Replaced missing power regulator transistor, voltage regulator IC, and volume control pot. Installed missing Sync Buss Controller and VRAM Addresser modules. Tested. Board was stuck in reboot. Replaced bad Sync Buss Controller socket and retested successfully but sound was garbled. Replaced bad PROM at 1M then repaired 2 burned edge connector traces with copper tape and retested.
Title: Re: Midway Games
Post by: channelmaniac on August 13, 2015, 09:09:55 PM
Model: Ms Pac Man
Symptom: Reboots and has garbled text/graphics.

Board would work fine without the Ms. Pac daughterboard installed but would be stuck with crashing and restarting upon installation of the daughterboard. Tested with a known good daughterboard and cable. Tested with a known good set of Z80 Sync Buss Controller and VRAM Addresser board and it would still crash at the attract screen and restart or would get stuck in a loop with a single "1" on the screen.

Replaced bad socket at 5F to fix the garbled text/graphics issue. Tested board with a known good set of ROMs. Board passed self tests but my BK 560A identified a bad 2114 RAM at 4K. Replaced the RAM and the crash/reboot still existed. Replaced the 74LS367 ICs at 6R and 6S thinking that maybe they had flaky inputs and that the extra buss length from the ribbon cable was causing the problem. It did not fix the issue.

The system would boot if the daughter card was installed but the 3 ROMs on it removed. It would also boot with a Two Bits Ms. Pac upgrade card at the end of the cable and with a 6-Pac upgrade board installed. Checked the 74LS42 at 7N and found that if pin 2 was probed the board would jump out of the stuck on "1" screen and start to reboot. Replaced the 74LS42 and the board immediately sprang to life.
Title: Re: Midway Games
Post by: channelmaniac on August 30, 2015, 04:00:30 PM
Model: Rampage World Tour
Symptom: Missing colors. Fails self test.

Replaced 5 missing SMT caps and 2 missing SMT coils to fix color issues. Replaced bad ROM and tested.
Title: Re: Midway Games
Post by: channelmaniac on August 31, 2015, 06:59:38 PM
Model: Mortal Kombat II
Symtpom: Dead. Lines on screen.

Reflowed custom DMA controller IC at UE13 and replaced dead battery. Set Free Play mode and tested. Board worked but the sound output was sputtery for the first minute. Recapped audio board and retested.
Title: Re: Midway Games
Post by: channelmaniac on October 18, 2015, 06:43:29 PM
Model: Galaxian
Symptom: Stuck in boot loop

If you watch it carefully it will flash "BAD ROM" on the screen between reboots.

Used a Fluke 9010A and ran checksums on the ROMs. Replaced bad ROM at 7U and retested.

Board was repaired as part of a "repair party" at the shop using one of the participants' Fluke 9010A in a hands-on walk-through of using it to repair a board. :)
Title: Re: Midway Games
Post by: channelmaniac on November 14, 2015, 12:00:26 AM
Model: Mortal Kombat II
Symptom: Dead.

Board had attempted repairs done to it.

Replaced CPU and Custom IC PLCC sockets, reflowed the custom DMA chip, and tested. Board booted with ROM errors. Installed missing ROM daughter board and retested only to find 2 ROMs not working on the daughterboard. Repaired a bad trace on the main board to fix the issue and tested.
Title: Re: Midway Games
Post by: channelmaniac on December 24, 2015, 09:13:10 AM
Model: Ms Pac Man
Symptom: Dead

Board was missing parts.

Board would not power up and had a short on the 5v line. Replaced shorted zener diode in the power supply to fix missing 5v. Installed missing CPU, Z80 Sync Buss Controller, VRAM Addresser, and 74LS161 at location 1E. Repaired power traces on the board's edge connector with copper trace tape. Tested board.

Board would now play but had distorted ghosts on the attract screen and the board would play Pac Man with a Ms Pac character that looked as if she was "walking on her lips." This was a ROM mismatch. The ROMs at 5E/5F were Ms. Pac character ROMs.

Pulled the ROMs and installed a customer supplied Super ABC 16-in-1 kit at their request. Retested board.
Title: Re: Midway Games
Post by: channelmaniac on January 11, 2016, 12:41:04 AM
Model: Pac Man w/6-Pac kit installed
Symptom: Garbage on screen and sometimes doesn't boot.

Reseated the ROM daughter board at 5E to fix the lines and garbage on screen. Cleaned the edge connector next to the CPU socket where the 6-Pac kit was plugged in. Tested.
Title: Re: Midway Games
Post by: channelmaniac on January 18, 2016, 09:48:29 PM
Model: Ms Pac Man
Symptom: Garbage on screen. Edge connector was heat damaged.

Repaired the edge connector with copper trace tape and tested. Board was not booting. Pushed down on the ROMs and noticed that when the ROM at 6J was pushed down it would boot. Removed the Mask ROM at 6J and noticed that pin 24 was broken. Replaced the Mask ROM with an EPROM and tested.
Title: Re: Midway Games
Post by: channelmaniac on January 20, 2016, 09:47:36 PM
Model: Ms. Pac Man
Symptom: Dead. Flashing garbage on screen.

Part of the garbage was the number 2. Replaced bad ROM at 6H and a hacked 2732 EPROM at 6F and tested. Board would play but was playing Ms. Pac Attack instead of Ms. Pac Man. Replaced a ROM at U6 on the daughterboard with one running original code. Tested.
Title: Re: Midway Games
Post by: channelmaniac on January 20, 2016, 09:49:21 PM
Model: Pac Man
Symptom: Dead. Nothing on screen.

Booted the board a couple of times and it showed vertically rolling garbage on the screen - it was missing some of the vertical clocking signals. Replaced a dead 74LS161 in the clock divider circuit at 2R and tested. Board was standard speed Pac Man. Replaced the ROM at 6F with the speed-up hack per customer request and retested.
Title: Re: Midway Games
Post by: channelmaniac on February 09, 2016, 07:16:57 PM
Model: Mortal Kombat 4
Symptom: Random problems

Board would play dead and not boot. When it would boot it would suffer random failures and reboots and sometimes a scrambled screen.

Board's failure was the result of a problem in the security chip circuit. The clock crystal would randomly stop and start oscillating. Reflowed cracked solder on the surface mount capacitors and 4MHz clock crystal. Power cycled board multiple times over several hours and ran it through 128 cycles of built-in burn-in tests.
Title: Re: Midway Games
Post by: channelmaniac on March 06, 2016, 03:40:07 PM
Model: Driving Force (Modified Galaxian board)
Symptom: Dead

Board was missing a jumper wire (and it was a terrible game) so the board was de-converted back to Galaxian. Removed all the kynar jumpers then pulled the ROM daughterboard and replaced it with a Galaxian one. Removed the stacked PROMs at 6L and replaced them with the proper PROM from a salvage board. Removed the stacked EPROMs at 1H and 1K and replaced the one at 1H with a mask ROM from a salvage board and 1K with a freshly programmed 2716 EPROM.

Board would boot but had no starfield, no color, no missiles, and both the ship and enemies were stuck in place on the screen. Resoldered cut pin 15 on the IC at 2B and cut pin 10 of 5E and tested. Replaced 2 bad 10,000uf capacitors in the power supply section and retested.

Goodbye Driving Force, hello Galaxian!
Title: Re: Midway Games
Post by: channelmaniac on March 18, 2016, 10:24:27 PM
Model: Pac Man
Symptom: Dead

Board had been modified with a single ROM conversion.

Removed conversion and patched a cut trace. Replaced the 2200uf radial capacitor someone installed with the proper axial type. Installed a 6-Pac kit on the board and tested.
Title: Re: Midway Games
Post by: channelmaniac on March 18, 2016, 10:26:01 PM
Model: Ms. Pac Man
Symptom: Dead

Replaced a bad CPU socket on the daughterboard. Game played but had garbled sound and the sprites moved incorrectly. Replaced a bad 7489 chip to fix the sprite movement and another 7489 in the sound circuitry. Repaired a burned power connection on the board edge connector and tested.
Title: Re: Midway Games
Post by: channelmaniac on March 18, 2016, 10:26:43 PM
Model: Ms. Pac Man
Symptom: Dead

Replaced 3 missing ROMs on row 6, repaired a burned edge connector, and tested.
Title: Re: Midway Games
Post by: channelmaniac on March 18, 2016, 10:36:22 PM
Model: Ms. Pac Man
Symptom: Dead

Replaced a bad ROM, 1 2114 RAM, and replaced the ribbon cable to the daughterboard. Repaired multiple burned traces on the edge connector. Tested.
Title: Re: Midway Games
Post by: channelmaniac on April 12, 2016, 09:46:34 PM
Model: Ms Pac Man
Symptom: Dead, blows fuses.

Replaced backwards 2200uf @ 25v capacitor in the sound section. Board ran but had no sound. Replaced audio amplifier chip and tested.
Title: Re: Midway Games
Post by: channelmaniac on April 16, 2016, 11:38:15 PM
Model: Ultimate Mortal Kombat 3
Symptom: Dead

Replaced a shorted U25 and tested. Graphics ROM 132 failed tests and had its quartz window shattered. Replaced the ROM and retested game.
Title: Re: Midway Games
Post by: channelmaniac on April 17, 2016, 09:04:19 PM
Model: Mortal Kombat 4
Symptom: Dead.

All four LEDs on the board were stuck on. Tested all the crystal oscillators and looked the board over for physical damage. Patched 7 cut traces between the RAM chips on the left edge of the board and tested. Dead. Checked the program ROMs and found one corrupted. Replaced both with revision 3 code and tested. The board booted and reported one bad sound ROM. Programmed a replacement ROM and played the game.
Title: Re: Midway Games
Post by: channelmaniac on April 19, 2016, 08:44:54 PM
Model: Mortal Kombat
Symptom: U99 Failed during self test

Board had liquid spill problems.

Cleaned board then replaced a bad socket on U115 and cleaned its pins. Checked traces under and replaced chips with corroded pins at U80, U81, U82, and U85. Patched a bad trace on pin 17 between U96 and U97 to fix the U99 failure during self test. Board would not save any data to battery backed SRAM. Patched bad trace between pin 20 of U49 and pin 12 of U39. Board played but was missing speech. Recapped audio board and tested.
Title: Re: Midway Games
Post by: channelmaniac on April 20, 2016, 10:38:41 PM
Model: Super Pac Man
Symptom: Dead

Replaced bad 74LS368 at 4A and the 16XX and its socket at 4B to fix the garbled clock signal. Board would boot but was stuck at the RAM/ROM OK screen but would periodically glitch and flip upside down. Replaced a broken resistor pack at RM1 which left a DIP switch bank floating. Board would boot and play but the colors for the motion characters were wrong. Pin 12 on the 74LS298 on the video board at 4L was stuck high. Replaced the resistor pack and tested.
Title: Re: Midway Games
Post by: channelmaniac on June 03, 2016, 08:13:04 PM
Model: Bosconian
Symptom: Stuck on RAM OK

Board had attempted repair damage and 3 jumper wires on the CPU board.

Removed the 3 jumper wires and replaced all of the 24, 28, 40, and 42 pin sockets and the unencapsulated resistor packs. Patched the 4 damaged traces under one of the EPROMs on the CPU board (previous repair tech missed one!), replaced a missing board standoff, and tested.
Title: Re: Midway Games
Post by: channelmaniac on June 03, 2016, 08:20:07 PM
Model: Bosconian
Symptom: Shows QAM 4 on the screen

Board had attempted repairs done. A previous tech replaced the socket on the 51xx IC and pulled a trace, but jumpered it under the sockets with blue Kynar wire. The two 6116 SRAMs on the video board had been resocketed, but this did not fix the RAM error.

A data bus line was shorted to ground through 48 ohm resistance. Traced it back to a bad 74LS368 on the CPU board. Replaced it and tested the game. Replaced all the 24, 28, 40, and 42 pin sockets and the unencapsulated resistor packs. Retested game and noticed a thump in the audio. Recapped the audio section and retested successfully.
Title: Re: Midway Games
Post by: channelmaniac on June 25, 2016, 03:16:41 PM
Model: Ms Pac Man
Symptom: Refresh board.

Board had leaking capacitors and a burned edge connector. Recapped board (2 x 10kuf, 1 x 2200uf, 2 x 470uf, 1 x 330uf, and 1 x 10uf axial electrolytic capacitors) and repaired the edge connector with copper trace  tape.
Title: Re: Midway Games
Post by: channelmaniac on July 03, 2016, 07:11:24 PM
Model: Mortal Kombat
Symptom: Static in audio

Recapped the audio board and tested
Title: Re: Midway Games
Post by: channelmaniac on July 03, 2016, 07:12:46 PM
Model: Mortal Kombat
Symptom: Dead. Stuck in reset.

Straightened several shorted pins on the EPROMs, checked the Program ROMs, and replaced a bad PLS153 logic chip at U40. Game played but had static in the audio. Recapped the audio board and retested.
Title: Re: Midway Games
Post by: channelmaniac on July 09, 2016, 08:35:49 AM
Model: Blitz 2000 Gold
Symptom: RAM Errors

Board had physical damage and was missing one RAM by the CPU.

This was a strange repair. The CPU RAM showed good, even though one was physically missing. Replaced missing RAM and jumpered 2 traces from a missing solder pad to the RAM. Board still showed video RAM errors. Reflowed lifted pins on the TMU video chip and tested.
Title: Re: Midway Games
Post by: channelmaniac on July 18, 2016, 09:20:11 PM
Model: Blitz 99
Symptom: Random video RAM errors, hangs on sound system tests, and random lockups/reboots

Replaced bad sound ROM to fix sound system issues. Reflowed U85 system controller IC to addresses lockup/reboot issues, and tested.
Title: Re: Midway Games
Post by: channelmaniac on July 18, 2016, 09:21:42 PM
Model: Ms. Pac Man
Symptom: Incorrect colors

Cleaned pins on PROM at 7F and tested. Recapped the board and replaced a broken monolithic cap at C34 on IC 4H. Tested.
Title: Re: Midway Games
Post by: channelmaniac on September 05, 2016, 03:30:25 PM
Model: Ms. Pac Man
Symptom: Dead

Someone had soldered up the contacts on the edge connector.

Removed excess solder from the edge connector and fixed several bad contacts with copper trace tape. Replaced bad ROMs at 6E and 6J and two bad 10,000uf capacitors in the power supply section. Tested.
Title: Re: Midway Games
Post by: channelmaniac on September 06, 2016, 10:41:16 AM
Model: Ms Pac Man
Symptom: Burned edge connector

Repaired the edge connector power and ground traces on the side next to the big heatsink with copper trace tape. Tested.
Title: Re: Midway Games
Post by: channelmaniac on September 16, 2016, 07:43:03 PM
Model: Cruis'N World
Symptom: Dead. Colored garbage on screen.

Reflowed custom DMA controller to restore life to game. Replaced bad 7407 IC in video output to restore missing video sync. Tested.
Title: Re: Midway Games
Post by: channelmaniac on October 16, 2016, 09:03:48 PM
Model: Ms Pac Man
Symptom: Dead. "P" on screen. Board had attempted repairs done.

Removed solder short from between a RAM data line and +5v on the VRAM Addresser socket
Title: Re: Midway Games
Post by: channelmaniac on October 16, 2016, 09:06:42 PM
Model: Super Pac Man
Symptom: I/O 1 error

Reseated the I/O chip at 4F on the board and tested.
Title: Re: Midway Games
Post by: channelmaniac on November 16, 2016, 07:14:03 PM
Model: Ms Pac Man
Symptom: Random crashes and reboots

Replaced hardened ribbon cable and bad Z80A CPU on daughter board. Tested.
Title: Re: Midway Games
Post by: channelmaniac on November 16, 2016, 07:15:37 PM
Model: Ms Pac Man
Symptom: Dead. Nothing on screen

Note: Board had been hacked to a 1 ROM version with no daughter board

Replaced missing Sync Bus Controller and dead PROM at 4A to restore video. Fixed damaged edge connector with copper trace tape and tested.
Title: Re: Midway Games
Post by: channelmaniac on December 19, 2016, 10:48:29 PM
Model: Mortal Kombat 4
Symptom: Dead

Replaced custom logic chip at U48 and tested.
Title: Re: Midway Games
Post by: channelmaniac on December 21, 2016, 08:25:33 PM
Mortal Kombat 4
Symptom: No blue or green on screen

Replaced a bad LT1260CS analog amplifier IC in the video output section and tested.
Title: Re: Midway Games
Post by: channelmaniac on January 20, 2017, 04:21:14 PM
Model: Jr. Pac Man (DC Conversion)
Symptom: Loses sound as it warms up

Sound would go sputtery after 1 to 2 minutes of playing. It was a digital failure and not an analog. Narrowed down the problem to the PROM at 5S using component cooler and replaced the prom with a freshly programmed 82S129 and tested.
Title: Re: Midway Games
Post by: channelmaniac on January 20, 2017, 10:07:08 PM
Model: Jr Pac Man (Field Kit)
Symptom: Missing colors, jerky movement of ghosts, missing music notes, bad sound effects

Replaced bad PROM at 9F with a freshly programmed 82S129 to fix the video issue. Replaced incorrect 330uf, 2200uf, and 14.7uf radial caps in the sound section with the proper axial ones, patched damaged traces on the 2200uf one, and replaced the physically broken volume control. Replaced the 7489 bipolar RAMs at 2H and 2J to fix the ghost movements. Checked the 7489 bipolar RAMs 7R and 7S by substitution and the 2 sound PROMs to no effect on the audio issues. Checked the 74xx logic in the sound section and found that when pin 1 of the 74LS157 at 6S and the 74LS158 at 6R were touched with the logic probe pin the game would go into a reboot loop. Replaced a bad 74LS163 at 2R to fix that issue. No dead gates were found so the sound section ICs were checked with an HP 10529a logic comparator. Replaced a bad 74LS283 at 6N that had a racing output on pin 10 to fix both sound issues and tested the game.
Title: Re: Midway Games
Post by: channelmaniac on January 27, 2017, 08:58:24 PM
Model: Rally-X
Symptom: Dead.

Replaced bad board interconnect cable and a missing standoff. Tested. Board was missing text during intro and yellow graphics during the game. Replaced a bad PROM at location 8P on the video board and retested successfully.
Title: Re: Midway Games
Post by: channelmaniac on February 11, 2017, 01:39:25 PM
Model: Ms Pac Man
Symptom: Dead

Replaced corroded pins on the bottom of the Z80 Sync Bus Controller, the socket that the controller fits into, and repaired cracked solder joins on the controller module. Replaced dead Z80A CPU and tested game without the daughterboard successfully but not with it. Replaced bad cable and cleaned corroded pins on a ROM on the daughterboard and restested successfully. Game played but ghosts and Pac were squares. Cleaned corroded ground pin on a character ROM and retested successfully.
Title: Re: Midway Games
Post by: channelmaniac on April 01, 2017, 09:26:48 PM
Model: Jr. Pac Man
Symptom: Static noise in audio and corrupt graphics

Replaced a bad 74LS139 at 4E and tested. Its outputs were racing.
Title: Re: Midway Games
Post by: channelmaniac on April 09, 2017, 07:04:00 PM
Model: Space Invaders
Symptom: White screen and hum in speaker.

Cleaned corroded ROM legs. Board would play but had lines across the rows of moving characters. Replaced a bad 74151 IC on the daughterboard and tested.
Title: Re: Midway Games
Post by: channelmaniac on April 09, 2017, 09:36:44 PM
Model: Space Invaders
Symptom: Intermittent Audio

Replaced 5 LM3900 ICs and the LM377 audio amp chip. Game died during testing. Replaced bad 8080A CPU that would fail after getting hot. Retested.
Title: Re: Midway Games
Post by: channelmaniac on April 22, 2017, 07:28:41 PM
Model: Space Invaders
Symptom: Garbage on screen

Removed the CPU and the board booted up to garbage instead of stripes, indicating a RAM issue. Replaced a 74157 driving the upper address lines on the RAMs and tested using the SI Test ROM. The board passed memory tests and most sound tests. The "extra" sound was a solid tone. Replaced a bad 556 timer IC and retested successfully.
Title: Re: Midway Games
Post by: channelmaniac on May 10, 2017, 08:11:40 PM
Model: Revolution X
Symptom: Will not save calibration or settings

Pin 20 of the SRAM IC had no signal. Traced it back to a corroded trace under a 74F138 IC. Patched the bad trace from Pin 20 of the SRAM IC to Pin 12 of the IC at U3. Tested.
Title: Re: Midway Games
Post by: channelmaniac on July 03, 2017, 03:00:36 PM
Model: Space Invaders Deluxe
Symptom: Dead

Board had no clock. Replaced 74160 at C7. Board booted but had no video. Replaced bad 10uf axial cap in the video output section and then had garbage on screen. Replaced 74174 with dead outputs at D7 and board was still dead, but had proper lines on the screen. Replaced bad RAM with a shorted output at H15 and tested. Board was making a very high pitched sound instead of the saucer sound. Replaced damage 28 pin socket on the sound IC and a shorted .1uf mylar cap next to it. Tested.
Title: Re: Midway Games
Post by: channelmaniac on July 09, 2017, 06:17:02 PM
Model: Space Invaders
Symptom: Dead. Short circuit on board.

Replaced shorted 22uf tantalum capacitor and tested. No audio. Replaced bad LM3900 next to the volume control. Tested.
Title: Re: Midway Games
Post by: channelmaniac on July 09, 2017, 06:19:34 PM
Model: Space Invaders Deluxe
Symptom: Dead

Replaced 2 x 9316B (74161) chips to fix the main board. Data line D2 was stuck low on the daughterboard with resistance of 22 ohms to ground. Replaced a shorted 74174 on the data shifter daughter card and the resistance raised to 326 ohms. Replaced another shorted 74174 on the daughterboard and tested the boardset.
Title: Re: Midway Games
Post by: channelmaniac on August 11, 2017, 09:58:28 PM
Model: M-4 Tank
Symptom: Dead

Replaced 8 bad orange ROM sockets and one bad orange CPU socket. Replaced the 8 bad 82S2708 OTP ROMs with 4 x 2716 EPROMs and reset the jumpers for memory type and address decoding. Replaced 4 old 10uf capacitors. Board would boot but had garbage on the screen. Replaced one bad 74174 and a bad 25S10 IC on the daughterboard. Replaced 4 LM3900 comparators to fix sound issues. Tested.
Title: Re: Midway Games
Post by: channelmaniac on August 26, 2017, 08:52:14 PM
Model: Pac Man (4-in-1 + High Score save hack)
Symtpom: Dead

Board had poor attempted repairs to the edge connector that caused it to not power up.

Repaired edge connector and booted game to see graphic corruption. Address line A2 was dead on the graphic ROMs on row 5. Patched damaged trace and tested.
Title: Re: Midway Games
Post by: channelmaniac on August 26, 2017, 10:15:30 PM
Model: Ms. Pac Man
Symptom: Dead

Repaired edge connector and replaced a bad ribbon cable connecting the daughter board. Tested.
Title: Re: Midway Games
Post by: channelmaniac on October 09, 2017, 03:49:16 PM
Model: Ms Pac Man
Symptom: Graphic corruption. Must get edge connector 'just right' to power on.

Jumpered gouged trace and repaired edge connector with copper trace tape. Tested.
Title: Re: Midway Games
Post by: channelmaniac on October 09, 2017, 03:52:07 PM
Model: Pac Man
Symptom: Graphic corruption, boxes on screen.

Replaced bad ROM at 5E. Board played but scoring at the top was corrupt. Replaced bad 74LS257 on the VRAM Addresser then repaired damaged edge connector with copper trace tape. Tested.
Title: Re: Midway Games
Post by: channelmaniac on October 21, 2017, 08:47:11 PM
Model: NBA Jam
Symptom: 2 ROMs fail self test

Jumpered 2 corroded traces and tested. Recapped audio board as these commonly have cap issues and retested.
Title: Re: Midway Games
Post by: channelmaniac on January 14, 2018, 04:08:14 PM
Model: Jr. Pac Man

Complaint of : "Garbage on screen. Rusted chips."

Turned off DIP 8 (freeze) and tested. Lines in some graphics, sound and motion graphics issues. The rusted chips were the 7489 bipolar 64-bit RAMs. Replaced all 4 and tested the board.
Title: Re: Midway Games
Post by: channelmaniac on January 31, 2018, 09:45:05 PM
Model: Mortal Kombat
Symptom: No audio

Board had attempted repairs done.

Found 1 damaged plated thru hole on U29 and 2 on U32. Patched the traces with Kynar wire and tested. Board had audio but it crackled and the audio amp chip would oscillate at high volume. Cleaned the board to fix the oscillation issue. Tracked the crackling back to the OKI audio chip and replaced it. Board had clear audio but the sound samples were corrupt sounding. Replaced bad sockets on U12 and U13 and cleaned the corroded pins on the sample ROMs to fix the sound samples. Tested.
Title: Re: Midway Games
Post by: channelmaniac on March 03, 2018, 09:56:56 AM
Model: Rampage World Tour
Symptom: Graphic corruption

The game played, but had graphic corruption on the screen. It was the kind where the dots on the screen would change randomly which indicated an open data line somewhere. When this happens you can use a 'well calibrated finger' to run across the various chip legs until the screen goes crazy. Found a missing signal on a pin of the Orbit chip where the trace went under the chip. Jumpered the broken trace with 30ga Kynar and tested.
Title: Re: Midway Games
Post by: channelmaniac on March 10, 2018, 09:37:02 PM
Model: Bosconian
Symptom: Dead. Parts boards.

Lone video board was missing 2 RAMs, 1 resistor, 1 PROM, and 1 03xx custom IC. Replaced missing parts, replaced the 24/28/42 pin sockets, and replaced the 10 pin resistor packs cobbled on the board with the proper 9 pin ones.

Took at Bosconian to Galaga conversion CPU board and de-converted it. Added the 50xx custom, 6116 SRAM, and 74LS245 ICs. Replaced all the 24/28/40/42 pin single wipe sockets with new dual wipe ones. Replaced all the old style resistor packs and replaced a missing 08xx custom IC. Tested with a known good Galaga video board. Replaced the Galaga ROMs with Bosconian ROMs and tested it with the video board.

Replaced the radial capacitors someone cobbled on the CPU board with proper axial caps and retested.
Title: Re: Midway Games
Post by: channelmaniac on April 06, 2018, 09:10:13 PM
Model: Mortal Kombat 4
Symptom: No sync

Board had a burned component on it.

Replaced a burned 0 ohm SMT resistor in the video ground circuit then replaced a 1000 ohm SMT resistor and a surface mount 7407 in the sync drive circuit. Tested.
Title: Re: Midway Games
Post by: channelmaniac on May 22, 2018, 03:00:29 PM
Model: Space Invaders
Symptom: Dead. Does nothing.

This was a horrible board to repair with failure upon failure to troubleshoot. Most of it was done with a logic probe then test ROMs, then an HP Logic Comparator to find the last dead gate.

Board blew fuse in my Kurz Kasch.

Replaced shorted tantalum capacitor in the audio amp circuit.

Blew fuse again

Replaced 2 shorted 1A diodes on the A board on the Kurz Kasch and replaced the fuse again. Excessive current draw killed the diodes.

ICs replaced:
C6 - 7442 - restored clock.
A5 - 7474 - restored divided clocks
A7 - 7404 - restored divided clocks
E7 - 74161 - restored divided clocks to RAM address lines
C4 - 74166 - restored video output
A6 - 7455 - restored video sync

Now that there's video, move on to why RAM looks bad and the CPU isn't running.

What looked like a couple of bad RAMs tested good in another board...

E4/D4 - 7404 - stuck outputs causing RAM read issues.
A1/C3/D7 - 74174 multiple stuck outputs
E3 - 7474 - Fixed stuck int causing CPU to never start
E2 - 7442 - Racing outputs causing ROMs to never read properly

Now it would boot the test ROM and pass tests but wouldn't boot the game ROMs. Tried a different test ROM and it failed the shifter test.

D6 - 7402 - Stuck output causing data to shifters to not be read back by CPU

ROM H - Wrong type for board... some odd mask ROM dated 1975
ROM F - Dead outputs.

Replaced the ROMs and tested successfully.
Title: Re: Midway Games
Post by: channelmaniac on May 22, 2018, 03:15:47 PM
Tip: Midway 8080 L board ROM replacement

When replacing mask ROMs or EPROMs on a Midway 8080 series board you have some options

1. Re-strap the board. In other words, change the jumpers to change what type of ROMs you are using. This is good if you're replacing all of the tri-voltage ROMs (2708 or TMS2716) or 9316B mask ROM.

This can be difficult as there are many different revisions of the board. I know from revision F and earlier the ROM selects go to different pins. Also, I've seen three different revisions of the board where the strapping points are different. Extreme care must be taken to not apply +12v and -5v to a standard EPROM or 9316 mask ROM so double check everything if you're doing the strapping on your own.

2. Replace a single ROM. If you want to replace 1 tri-voltage ROM, well, you either better be able to program a replacements (I can...) or go back to option 1. For 9316B you can either replace it with a 2732 with the image stacked in the ROM (0-7FF and again from 800-FFF) or with a 2716 EPROM that has been modified.

The 2716 requires pin 21 to be tied high and on the 9316B it is tied low. To modify the 2716 EPROM, program it first, then bend pin 21 out parallel with the chip body and cut it short. Take a piece of Kynar wire and jumper from pin 21 to pin 24 (+5v) to tie the PGM pin to +5v. Now it can be plugged into the socket to take the place of a bad 9316B without having to restrap the board.
Title: Re: Midway Games
Post by: channelmaniac on June 02, 2018, 10:26:17 PM
Model: Bosconian
Symptom: "Parts board"

Board came in missing a lot of ICs.

Replaced all 24, 28, 40, and 42 pin sockets and 3 of the old style resistor packs. Replaced 7 missing program ROMs, 2 missing 8xx customs, 1 missing 6xx custom, 1 7xx custom with bad leg rot, 1 missing 5xx custom, Installed 3 missing resistor packs, 1 missing 74LS368, and a missing video PAL. Installed 3 missing sound ROMs, replaced a video ROM with bad leg rot, installed a missing audio amp chip, and a missing coin counter driver transistor, installed 4 correct standoffs, and replaced the ribbon cable to finish the board and tested successfully.
Title: Re: Midway Games
Post by: channelmaniac on June 02, 2018, 11:25:25 PM
Model: Bosconian
Symptom: Dead

Replaced all the 24, 28, 40, and 42 pin sockets, then replaced all the old style, unencapsulated resistor packs. Replaced 5 bad mask ROMs with leg rot. Replaced 2 8xx customs and 1 7xx custom with leg rot. Replaced two broken standoffs. Boardset would boot then crash at RAM OK. Replaced bad CPU 2 and re-tested. Board ran but hand sparkling text on the left side of the screen. Replaced a bad 3xx custom at 4N on the video board and retested successfully.
Title: Re: Midway Games
Post by: channelmaniac on June 03, 2018, 08:22:04 PM
Model: Bosconian
Symptom: Dead

Replaced the 24, 28, 40, and 42 pin sockets on the board. Tested.
Title: Re: Midway Games
Post by: channelmaniac on June 06, 2018, 09:09:07 PM
Model: Galaga
Symptom: RAM Error 2L

Replaced bad 2114 RAM and tested.
Title: Re: Midway Games
Post by: channelmaniac on July 01, 2018, 07:08:37 PM
Model: Space Invaders
Symptom: Dead

Replaced 2 shorted Tantalum caps, 1 missing cap, and one physically broken cap. Board would then power up but had garbage on the screen and was stuck in watchdog. Replaced 2 x 74161 in the reset circuit on the upright board to fix stuck in reset issue. Board was still powering up with garbage. Replaced a bad 74174 and 74153 and board would boot the test ROM but fail every single RAM chip. Replaced bad 74157 and board would boot but was missing all sounds. Replaced the LM3900 at L2-3 and the saucer sound and bass notes were the only sounds working. Replaced all remaining (6!) LM3900 chips to restore all sound effects. Tested.
Title: Re: Midway Games
Post by: channelmaniac on July 21, 2018, 11:19:02 PM
Model: NBA Jam
Symptom: No Audio

Recapped the audio board and tested.
Title: Re: Midway Games
Post by: channelmaniac on July 21, 2018, 11:21:34 PM
Model: Mortal Kombat II
Symptom: No Audio

Board had bad corrosion damage on the ROMs and their sockets.

Removed all 8 of the ROM sockets and all 6 ROMs from the sound board. Cleaned the board, recapped it, installed 6 new sockets, and cleaned the ROM legs. Replaced ROMs at U5 and U7 which had some missing legs and tested. Nothing, yet the heatsink was warm. Replaced the MB3731 audio amp IC and successfully tested the game.
Title: Re: Midway Games
Post by: channelmaniac on August 06, 2018, 09:53:55 PM
Model: Space Invaders
Symptom: Dead

Board arrived with the clock crystal bent over and one leg pulled out of the board. Carefully straightened the pins on the crystal and reinserted it into the board and it showed flickering garbage on the screen. Replaced a bad 74LS157 at F7 to fix a racing address line issue. Changed the ROM strapping to convert the board from using TMS2716 EPROMs to 2732s. Replaced bad RAMs at G12 and H12 because of missing outputs and RAMs at G13 and H13 because of distorted output signals. The board would then boot a diagnostic ROM. Replaced bad RAMs at G8, G10, H11, G14, H14, and H15. Inserted freshly programmed 2732 EPROMs then tested board successfully. Socketed the remaining 6 original RAMs at the customer's request and burned the board in for a few hours.
Title: Re: Midway Games
Post by: channelmaniac on August 11, 2018, 06:41:29 PM
Model: Space Invaders
Symptom: Dead

Replaced shorted capacitor in the audio amplifier circuit and tested.
Title: Re: Midway Games
Post by: channelmaniac on August 11, 2018, 09:32:45 PM
Model: Space Invaders
Symptom: Dead, attempted repair damage.

Board had attempted repair damage where someone tried to replace the audio amplifier IC.

Jumpered a broken trace between pin 9 and pin 6 of the LM377 audio amplifier IC, replaced the 10uf tantalum cap next to it, and powered up the boardset to find no video output. Board had all the right signals on the 74166 and the 74LS55. Replaced the 10uf capacitor in the video output circuit and the video was restored, but the game was stuck with lines on the screen. Replaced the 8080A CPU and the game would play, but had no audio. Replaced bad LM3900 at L2-L3 and audio was restored but was intermittent. Replaced C44 and retested. Intermittent audio. Inspected the board and found a cracked solder joint on C45 and resoldered it to restore the audio output.

Board had audio but was just a loud hum. Replaced the 7417 at F5 to restore the thump thump sounds and fix the stuck hum. Board had no other sounds. Replaced all the LM3900 ICs which fixed some sounds. The invader hit sound was chirpy, the missile sound was high pitched, and the explosion sounds were missing. Resoldered a cracked solder joint on C18 to fix the saucer sound and replaced a bad 4006 IC at N5 to fix the explosion and missile sounds.
Title: Re: Midway Games
Post by: channelmaniac on August 12, 2018, 02:31:24 PM
Model: Space Invaders
Symptom: Dead, no video

Clocks were missing. Replaced a dead 9310 in the clock circuit and tested. No video, but had clocks. All address lines and clock decoders were working, but all 16 RAMs had no outputs. Pulled one RAM and it tested good in a NeoLoch tester. Checked and found the WE line for the RAM stuck low. The Intel clock driver chip for the CPU had 2 dead outputs. Checked the inputs and found 2 dead ones. Replaced a bad 74157 to restore the missing signals, reinstalled the RAM that was pulled, and tested the game.
Title: Re: Midway Games
Post by: channelmaniac on September 22, 2018, 10:46:28 AM
Model: Mortal Kombat II
Symptom: Graphics corruption

Reflowed the custom DMA chip at UE13 and tested.
Title: Re: Midway Games
Post by: channelmaniac on December 27, 2018, 09:01:32 PM
Model: Ms. Pac Man
Symptom: Dead. Garbage on screen

Garbage did not always show upon power on. Replaced the 74LS368 clock generator IC and tested. Board was stuck on garbage, but clock was now stable. Replaced bad Z80A CPU and tested.
Title: Re: Midway Games
Post by: channelmaniac on December 27, 2018, 09:03:13 PM
Model: Ms. Pac Man
Symptom: Stuck in boot loop

Board sometimes flashed 'BAD' <something> but was doing it so fast it couldn't be read. Cleaned the inside surface of the program ROM legs and tested. Still in boot loop. Removed the RAM and tested it off board in a BK 460A IC tester and found one bad IC. Reinstalled the RAM and replaced the bad one then tested the game.
Title: Re: Midway Games
Post by: channelmaniac on March 05, 2019, 09:23:06 PM
Model: Mortal Kombat II
Symptom: Static in audio

Owner had replaced all the radial caps, but not the axial. Replaced 11x 10uf @ 25v axial capacitors and tested.

Note: The blue Phillips axial caps used do tend to dry out and cause static.

Hand delivered this to the site and noticed the game had a horrific hum when the board was installed. Had the owner replace the power supply to finish fixing his game.
Title: Re: Midway Games
Post by: channelmaniac on March 31, 2019, 08:46:17 PM
Model: Space Invaders
Symptom: Dead, Garbage on screen

CPU was stuck in reset. The /RESET line was shorted to ground. Replaced a dead 7404 at F3, 74161 at E2, 74161 at D2, 7442 at E3, 74175 at B5, 74174 at C5, 74174 at E5, and 74174 at E4. Basically every chip on the /RESET line, except one 74174 at C5 was shorted between the /RESET input and ground. The 74161 chips were dead on pin 10 and the 7442 at E3 was connected to pin 10 on those 74161. Looks like a voltage spike came through the Power Supply Reset line to the board.

Board would now play but was missing the Saucer Hit and the Invader Hit sounds. Replaced bad LM3900 chips at M4, M5, K4, and K5 to restore sound.
Title: Re: Midway Games
Post by: channelmaniac on April 02, 2019, 07:27:46 PM
Model: Space Invaders
Symptom: Dead

Note: Unit had a single ROM mod kit installed. The board had that kit and another IC floating around on top of the board.

Straightened the pins on the ROM socket, placed the plastic cap back on top of it, and reinserted the ROM mod board. Straightened the pins on the smaller floating IC and reinserted it back into its socket. Replaced an improper (wire wrap!) RAM socket, one bad RAM, and tested. The Invader Hit sound was distorted. Replaced 2 LM3900s and it was still distorted. Found a lead on a mylar capacitor that was not soldered properly to the board - a 40 year old factory soldering error. Resoldered the capacitor and successfully tested the game.
Title: Re: Midway Games
Post by: channelmaniac on April 06, 2019, 11:46:25 AM
Model: Space Invaders
Symptom: "RAM 4 Error, not the RAM"

All four ROMs were shorted to ground on D3 and D4 of the data bus. This took out a 74153. Replaced the 153 and still had the error. A 74174 between the RAM data bus and the bad 74153 on the Program Data Bus and an output racing. Replaced it to clear the RAM error. Replaced all 4 Program ROM and tested. Board was missing the Invader Hit sound and the Missile shot sound. Replaced 4 LM3900 ICs to fix the sounds and tested.
Title: Re: Midway Games
Post by: channelmaniac on April 07, 2019, 12:55:52 PM
Model: Space Invaders
Symptom: Dead. Garbage on screen.

Replaced 74S04 in the clock circuit and resoldered the crystal socket and capacitor to fix intermittent clock issues. Replaced 74LS08 at F2 that had 2 bad outputs to restore game to operation. Replaced 3 LM3900 ICs to fix the missing sounds. Tested.
Title: Re: Midway Games
Post by: channelmaniac on April 08, 2019, 09:50:13 PM
Model: Ms. Pac Man
Symptom: Dead

Replaced broken ribbon cable and tested. Player 1 controls would not work during game and would coin up the game in attract mode. Replaced bad 74LS367 at 8E and tested.
Title: Re: Midway Games
Post by: channelmaniac on April 08, 2019, 09:51:15 PM
Model: Ms. Pac Man
Symptom: No audio

Recapped the audio section and replaced a bad audio amplifier chip. Audio worked but was fuzzy sounding and had a repeating thump to it. Replaced missing capacitor at C50 and tested.
Title: Re: Midway Games
Post by: channelmaniac on April 08, 2019, 09:58:17 PM
Model: Ms. Pac Man
Symptom: Intermittent sprite issues

Board had previous repair damage where at tech used sandpaper on the top and bottom side where 2 chips were removed and replaced. Pulled off 2 ICs - 74LS74 at 3N and a 74LS377 at 4B and inspected previous repairs. Replaced the sockets and reinstalled the ICs.

The board problem was that it would go from having sprites to having a whole row of the same sprite to static on the screen instead of the sprites when bumped, tapped, or flexed. Traced it back to the /HBLANK signal (horizontal blanking) as it went into the AND gate at 5N. Touching that input made the screen change. Replaced the 74LS08 at 5N and tested.

The 74LS74 at 3N that the previous tech replaced was the source of the /HBLANK signal. They were on the right track, but missed the bad gate.
Title: Re: Midway Games
Post by: channelmaniac on April 09, 2019, 09:23:18 PM
Model: Space Invaders Deluxe
Symptom: Dead, garbled screen

With the H ROM pulled, instead of vertical lines on the screen, the lines were horizontal. This is indicative of a CPU area issue on the boardset.

Replaced bad CPU. Replaced 2 bad 74LS08 on the address lines of the CPU. The READY line was not working properly so the 7474 driving it was replaced. Checked the address lines and data in/out of the RAMs and they were OK. Replaced a bad 8216 data bus latch on the lower CPU data lines - 2 of the 4 lines on it were stuck low.

Game would now boot and play but was missing all of the LM3900 based sounds. Replaced all LM3900s and the sounds returned, but the invader hit and missile sounds were very short in duration and the UFO hit sound was garbled. Replaced 4 bad Tantalum capacitors in the sound section to fix the short sounds and the garbled sound issue. Tested.
Title: Re: Midway Games
Post by: channelmaniac on April 13, 2019, 06:17:18 PM
Model: Pac Man
Symptom: Dead

Replaced 6 bad 2114 RAMs. Board would boot but had no sound. Replaced LM1877 amp and 3 capacitors in the audio circuit. Board had audio but it was just beeps and blips. Replaced a bad 7489 bipolar RAM and tested.
Title: Re: Midway Games
Post by: channelmaniac on April 13, 2019, 06:18:47 PM
Model: Pac Man
Symptom: Solid red screen and thumping noise

Replaced bad 2125 RAM. Screen was now solid white. Replaced bad 74LS158 in the video output section to fix video. Replaced 3 electrolytic caps and C50 in the audio circuit to fix the thumping. Tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2019, 09:26:00 PM
Model: Clowns
Symptom: Dead

Replaced bad 74LS08 address line buffer and CPU socket. Replaced 3 bad LM3900 and a bad LM377 amplifier in the audio section. Tested with inconsistent results. Replaced 2 corroded sockets and the bank of DIP switches and retested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2019, 09:26:32 PM
Model: Ms Pac Man
Symptom: Split screens

Replaced bad 74LS161 clock divider chip and tested.
Title: Re: Midway Games
Post by: channelmaniac on May 07, 2019, 09:27:05 PM
Model: Ms Pac Man
Symptom: Stuck in Reset

Replaced bad 74LS161 and 74LS02 in the reset circuit and tested.
Title: Re: Midway Games
Post by: channelmaniac on May 11, 2019, 11:23:42 PM
Model: Pac Man
Symptom: Tearing screen, won't boot

Replaced 74LS161 at 3R to fix the tearing screen. Replaced 74LS161 at 9C to fix stuck reset line and get game to boot. Replaced broken resistor pack at RM5 to fix missing sound. Tested.
Title: Re: Midway Games
Post by: channelmaniac on May 11, 2019, 11:24:43 PM
Model: Ms Pac
Symptom: Dead

Replaced 3 large wire jumpers with Kynar wire and bridged 2 broken traces between the CPU and ROMs. Reinserted a backwards RAM chip and tested. Luckily the RAM was not damaged.
Title: Re: Midway Games
Post by: channelmaniac on May 11, 2019, 11:28:20 PM
Model: Ms Pac Man
Symptom: Distorted blue screen and intermittent boot

Replaced 74LS161 at 3R to fix distortion. Replaced bad PROM at 7F to fix blue screen issue. Tested. Replaced bad socket at 4K to fix boot issue. Tested. Board output the wrong colors on the screen - they looked like pastels. Removed short from pin 9 of the PROM at 4A and retested. Replace bad 74LS86 at 4F as the output did not follow the input and was causing the PROM at 3M to output data at the wrong time. Tested.
Title: Re: Midway Games
Post by: channelmaniac on May 12, 2019, 04:34:18 PM
Model: Ms. Pac Man
Symptom: Dead

Previous tech replaced the CPU and Sync Buss Controller sockets.

Looked over the board and discovered the tech didn't finish soldering all the pins on the CPU socket. Finished soldering the CPU chip and checked continuity to see what the tech messed up. Jumpered a bad trace on Data line D1 from the Sync Buss Controller to the CPU and from the CPU to the edge connector.. Game would boot from a ROM attached to the edge connector, but not from row 6. Replaced bad 74LS42 decoder IC driving the chip enables and tested. Game played but had dots on the screen. Reprogrammed the character ROM at 5E as it had suffered from bit rot. Patched a burned trace to the edge connector and tested game.
Title: Re: Midway Games
Post by: channelmaniac on May 15, 2019, 06:19:54 PM
Model: Space Invaders Deluxe
Symptom: Dead

Replaced 74161 and 7442 (address decoder) ICs, 4 ROM sockets, and the CPU socket. Board would boot but would crash immediately and reboot. Installed a missing ROM at D1 and tested. Board played but was missing the explosion sound. Replaced a bad LM3900 at K3-4 and tested.
Title: Re: Midway Games
Post by: channelmaniac on June 02, 2019, 03:05:49 PM
Model: Midway 8080 Motherboard
Symptom: Dead

Replaced missing 74LS00 at BX and tested
Title: Re: Midway Games
Post by: channelmaniac on June 02, 2019, 03:07:51 PM
Model: Midway 8080 Motherboard
Symptom: Dead

Replaced bad 74LS00 at B6 and 4 bad LS08 at H3, G3, F3, and F2. Tested.
Title: Re: Midway Games
Post by: channelmaniac on June 02, 2019, 03:09:54 PM
Model: Midway 8080 Motherboard
Symptom: Dead

Replaced 74166 at C4 and 4 10uf capacitors. Replaced 2 74LS 08 at H3 and F2. Replaced 7442 at E2 and tested.
Title: Re: Midway Games
Post by: channelmaniac on June 02, 2019, 03:11:05 PM
Model: Midway 8080 Motherboard
Symptom: Dead

Replaced dead CPU. Replaced bad 74LS157 at F4. Tested.
Title: Re: Midway Games
Post by: channelmaniac on June 02, 2019, 03:15:35 PM
Model: Midway 8080 Motherboard
Symptom: Dead

Replaced dead 74LS174 at A3, C3, and D7. Replaced corroded blue CPU socket with a standard dual wipe. Looked at memory outputs and getting strange results. Replaced chattering 74LS04 at D4 and E4. Address lines were still not quite correct. Replaced bad 74LS161 at D5 to fix. The data bus was still locked on a bit to the CPU and a bit to the RAM - Replaced the 8216 bus latches at B3 and D3 to fix. Tested and burned in board.
Title: Re: Midway Games
Post by: channelmaniac on December 25, 2019, 10:44:12 PM
Model: Pac Man
Symptom: Random reboots

Board was true to the description and would randomly reboot. Cleaned dirty CPU pins and tested. Nope. Fixed cracked solder joints on the Z80 Sync Buss Controller. Nope. Checked the 161/163 clock dividers, sync buss daughterboard, VRAM Addresser daughterboard, and program ROMs by substitution - nope. Dug deeper into the CPU circuit and checked the /NMI, /IRQ, and /RESET lines. All were good and it wasn't a watchdog reset. Checked the CPU clock and found it was very distorted sounding on the logic probe. Replaced the 74LS368 in the clock circuit and successfully tested the game.
Title: Re: Midway Games
Post by: channelmaniac on December 27, 2019, 04:07:14 PM
Model: Ms Pac Man
Symptom: Burnt edge connector

Repaired edge connector. Game would not boot. Repaired broken leg on ROM at 6H. Game would boot but there were no moving sprites on the screen. Replaced bad 74LS161 at 1E and tested.
Title: Re: Midway Games
Post by: channelmaniac on December 27, 2019, 04:08:52 PM
Model: Ms Pac Man
Symptom: Flashing 1 on screen. Remove operator hack.

Removed the operator hack and installed a replacement 74LS74 and socket at 8C as it was modified for the hack. Replaced missing ROM at 6F to fix the flashing 1 error. Tested.
Title: Re: Midway Games
Post by: channelmaniac on December 27, 2019, 04:22:30 PM
Model: Pac Man
Symptom: Stuck in boot loop

Pulled ROMs and used an external 6-in-1 ROM to test. Board booted the menu but was missing characters. Replaced bad RAM at 4P and tested. Reinstalled ROMs on Row 6 and tested.
Title: Re: Midway Games
Post by: channelmaniac on March 08, 2020, 07:13:01 PM
Model: Pac Man
Symptom: No Sync

Replaced bad 74LS161 at location 2R and tested. Pin 15 of 2R (Carry) was stuck low causing the LS161 at 2S to have no output.
Title: Re: Midway Games
Post by: channelmaniac on April 09, 2020, 10:45:59 PM
Model: Rally-X
Symptom: Dead

It had the orange socket for the Sync Bus Controller IC and the IC had weak legs. Tap it and the game would try to boot. Pulled it and two legs bent over, barely hanging on. Soldered it to a machine pin socket to save it then reinserted it back into the socket.

Board would then try to boot but had corrupt graphics on the screen and would reboot if you tapped the mask ROMs on the CPU board. Replaced all the mask ROMs with 2532 EPROMs.

Game was now stable but had corrupt text and border graphics. Found the 2532 on the video board had pin 18 (/CE) stuck high. Traced it back to a broken connection on pin 44 (5th from the end on the middle connector) of the wire harness. Replaced the broken connector and tested.

Title: Re: Midway Games
Post by: channelmaniac on April 27, 2020, 10:55:31 PM
Model: Midway Y-Unit
Info: Pinout for custom U99 IC

Had a board to repair that was a major ordeal... and while working on it I had to figure out why U99 was showing as bad, when it was not. Pinned out the IC based on the schematic, a multimeter for power/ground pins, and trace following. Hope you find it helpful.
Title: Re: Midway Games
Post by: channelmaniac on April 28, 2020, 10:45:31 PM
Model: Trog
Symptom: Dead

Board had some very strange repair work done using enamel coated magnet wire covered in silicone caulk.

Board was stuck in watchdog. Found pin 17 of one 4464 DRAM shorted to +5v. Tracked it down to a bypass capacitor lead pushed against the board and shorting to the trace. Fixed that. The board would boot to a U99 error, no voice/DAC sound, corrupt graphics, and bad colors. Traced out connections, they were all good. Tracked down the U99 error and part of the graphic corruption to an issue that would come and go when the board was flexed. Narrowed it down to a small area under the silicone.

Removed all the silicone and magnet wires. Straightened up multiple bent chip legs and installed much shorter Kynar wire jumpers to fix the U99 error. Replaced a corroded CPU socket then removed extraneous video RAM from the sockets on the board to fix the color issues. Replaced the axial caps and 4 1458 Op Amps to restore all sounds. Tested.
Title: Re: Midway Games
Post by: channelmaniac on May 22, 2020, 09:31:06 AM
Model: Space Invaders
Symptom: Dead. Flickering screen

Cleaned tarnished pins on a socketed 74160 in the clocking circuit to fix the flickering. Fixed a bent pin on ROM E causing the ground pin to not make contact. Tested.
Title: Re: Midway Games
Post by: channelmaniac on June 04, 2020, 06:40:44 PM
Model: Ms Pac Man
Symptom: Dead

Replaced shorted Sprite RAM at 2A and 2B, bad 74LS161 clock dividers at 3R and 3S and bad 74LS368 clock driver IC at 8B. Tested. Board would not boot. Replaced bad 74LS139 on the Sync Bus Controller and tested.
Title: Re: Midway Games
Post by: channelmaniac on June 07, 2020, 06:38:15 PM
Model: Mortal Kombat 3
Symptom: ROM errors, garbage on screen.

Cleaned multiple corroded ROM legs. Repaired a rusted off leg on one EPROM. Reprogrammed 3 ROMs to resolve their errors. Repaired 2 gouged traces to finish the ROM error repairs. Patched a corroded trace to fix the graphic corruption issues. Replaced bad TL084 op-amp in the audio output circuitry to restore sound.
Title: Re: Midway Games
Post by: channelmaniac on June 07, 2020, 06:39:20 PM
Model: Mortal Kombat 3
Symptom: U49 CMOS RAM Error

U49 is not the backup RAM, U63 is. Replaced bad backup RAM only to have the power to it disappear. Patched a corroded trace and tested.
Title: Re: Midway Games
Post by: channelmaniac on October 08, 2020, 10:02:51 PM
Model: Ms Pac Man
Symptom: No sprites on screen

Traced backwards from the motion RAM circuitry to find the 74LS174 at 1K had a stuck output on pin 15. Replaced the IC and tested.
Title: Re: Midway Games
Post by: channelmaniac on October 21, 2020, 03:34:53 PM
Model: Mortal Kombat II
Symptom: All graphics ROMs fail testing

Board had attempted reflow done to the custom DMA controller IC.

Upper address line signals were missing off the Graphics ROMs. Fixed a shorted pad and reflowed the 2 sides of the custom that someone had attempted before. Replaced bad 74LS374 at UE17 and bad PAL at UE18. Tested.
Title: Re: Midway Games
Post by: channelmaniac on October 21, 2020, 10:13:33 PM
Model: Mortal Kombat II
Symptom: Dead. Missing ROMs

Programed replacement program ROMs and installed them to find graphics corruption. Replaced bad RAM at UB11 and tested. Board failed CMOS RAM tests. Patched bad trace to the RAM's /CE line but that did not fix the issue. Replaced the CMOS RAM and tested.
Title: Re: Midway Games
Post by: channelmaniac on October 21, 2020, 11:33:06 PM
Model: Mortal Kombat II
Symptom: Dead. Missing parts.

Patched gouged trace and replaced missing program ROMs and a missing PAL. Board would boot but ROMs tied to data bits 0-7 would pass but 8-31 would not. Replaced 3 bad 74ALS245 chips at UH13, UF15, and UF16 and tested.
Title: Re: Midway Games
Post by: channelmaniac on October 25, 2020, 09:58:11 PM
Model: Galaxian
Symptom: No moving enemies

This one was interesting. Someone replaced some of the attack RAM with the wrong type. Three of the 27LS00 (256 x 1 bit) RAMs were replaced with 82S25 which are 16 x 4 (64 bits) and of the wrong pinout. Replaced the three RAMs with 82S16, a compatible RAM and tested.
Title: Re: Midway Games
Post by: channelmaniac on October 25, 2020, 09:58:33 PM
Model: Galaxian
Symptom: Hum

Recapped board and tested.
Title: Re: Midway Games
Post by: channelmaniac on October 25, 2020, 09:59:26 PM
Model: Galaxian
Symptom: Squished enemies and double text on screen

Replaced a missing character ROM at 1K and 74LS86 chips at 4B and 5B. Tested.
Title: Re: Midway Games
Post by: channelmaniac on October 25, 2020, 10:01:54 PM
Model: Pac Man
Symptom: Garbage on screen

Replaced a bad RAM at 4N and three bad ROMs at 6E (dead), 6F (pin rot), and 6H (pin rot.) Repaired a burnt edge connector and replaced the power caps. Tested board and found the ROMs at 5E and 5F were for Ms. Pac Man. Replaced them at the customer's request with Pac Man versions.
Title: Re: Midway Games
Post by: channelmaniac on November 16, 2020, 12:14:44 AM
Model: Galaga
Symptom: Dead

Replaced all the old style 24, 28, 40, and 42 pin sockets with good quality dual wipe sockets and replaced unencapsulated resistor packs. Replaced missing ribbon cable and tested. Board would crash like crazy and had clock issues. Replaced bad 6116 SRAM and retested. Replaced bad 74LS368 on the video board and CPU board. Replaced bad 74LS107 on the CPU board. Board still had an unstable main clock after 3 bad ICs were replaced. Replaced the main crystal and had a solid clock afterwards, but the board would still crash. Replaced bad bipolar PROM at 5C and tested.
Title: Re: Midway Games
Post by: channelmaniac on November 16, 2020, 12:16:06 AM
Model: Galaga
Symptom: Dead

Replaced all the old style 24, 28, 40, and 42 pin sockets with good quality dual wipe sockets and replaced unencapsulated resistor packs. Replaced a missing 00xx custom and missing L ROM. Board would boot but had no sound. Replaced sound amplifier IC and tested.
Title: Re: Midway Games
Post by: channelmaniac on November 16, 2020, 12:17:57 AM
Model: Galaga
Symptom: Dead

Replaced all the old style 24, 28, 40, and 42 pin sockets with good quality dual wipe sockets and replaced unencapsulated resistor packs. Replaced 6 missing 2114 RAMs and tested. Board would boot but crash during attract mode. Replaced incorrect ROM at 3L (Namco code vs. the other ROMs having Midway code) to fix that issue. Audio played but had a thumping in it. Recapped the audio section and retested.
Title: Re: Midway Games
Post by: channelmaniac on November 16, 2020, 12:19:43 AM
Model: Galaga
Symptom: Bad Audio

Board had previous repair attempts.

Replaced 4 24-pin sockets and 3 28-pin sockets with good quality dual-wipe sockets to get the boardset stable. Replaced a bad 7489 RAM at 2A to fix the audio issue.
Title: Re: Midway Games
Post by: channelmaniac on November 23, 2020, 11:27:54 PM
Model: Pac Man
Symptom: Stuck in boot loop

Replaced bad 2114 and tested. Recapped board and retested
Title: Re: Midway Games
Post by: channelmaniac on November 23, 2020, 11:28:27 PM
Model: Pac Man
Symptom: Hums

Recapped PCB and checked the rectifier diodes. Tested.
Title: Re: Midway Games
Post by: channelmaniac on November 23, 2020, 11:29:17 PM
Model: Pac Man
Symptom: Incorrect colors

Replaced incorrect PROMs at 7F and 4A. They were from Pac Man Plus. Recapped the PCB and repaired a burnt edge connector. Tested.
Title: Re: Midway Games
Post by: channelmaniac on November 23, 2020, 11:33:31 PM
Model: Pac Man
Symptom: Incorrect colors and no sound

Board had previous attempted repairs with some damaged traces.

Recapped the PCB then replaced the Pac Man Plus PROMs at 7F and 4A to fix the color issue. Replaced a bad 7489 and 4066 in the sound circuit. Fixed a broken trace under the socket of the 74LS273 and replaced both the socket and the 273. Still no sound. Started tracing through the rest of the previous work done and found the resistor pack on the PROM at 3M was installed backwards, tying the Open Collector outputs of the PROM to ground instead of tying them to +5v.  Replaced the 6 pin resistor pack with a 5 pin and installed it properly to fix the sound issue. Tested. Board would intermittently not read the DIP switches properly and moving the joystick would cause the game to step to the next level. Replaced a bad socket and the 74LS138 at 7J and retested successfully.
Title: Re: Midway Games
Post by: channelmaniac on November 23, 2020, 11:35:22 PM
Model: Ms Pac Man
Symptom: Random reboots.

Recapped PCB and fixed burnt edge connector. Replaced bad ribbon cable to daughterboard and tested.
Title: Re: Midway Games
Post by: channelmaniac on November 25, 2020, 02:26:09 AM
Model: Ms Pac Man
Symptom: Reboots at random

Board was DC converted

Replaced missing diodes at D7 and D7, missing 4 ohm 10 watt resistor, and repaired the burnt edge connector. Replaced dirty sockets at 6H and 6J that had some kind of spill down inside them. Tested. Recapped PCB and retested.
Title: Re: Midway Games
Post by: channelmaniac on November 25, 2020, 11:16:16 PM
Model: Pac Man
Symptom: No Green Output

Board had attempted repair damage.

PCB arrived dead. Replaced bad previously replaced 74LS161 at 3S and patched two damaged traces under it. Replaced power caps and tested. Cleaned legs on the PROM at 4A to fix graphic and color issues. Board would run but would reset at random. Tapping the board would also cause it to reset. Discovered that the 10uf cap in the reset circuit was bad and you could make the board reset at will by simply tapping it lightly. Replaced cap and tested.
Title: Re: Midway Games
Post by: channelmaniac on November 25, 2020, 11:37:02 PM
Model: Ms Pac Man
Symptom: Intermittent graphic corruption and reboots

Repaired the edge connector and recapped the PCB. Reflowed bad solder joints on the Sync Bus Controller to fix the reboot issue and bad solder joints on the VRAM Addresser module to fix the graphic corruption issues. Tested.
Title: Re: Midway Games
Post by: channelmaniac on November 26, 2020, 11:31:25 PM
Model: Ms Pac Man (ROM Hack Pac Man)
Symptom: Crashes / Reboots

Replaced 2 corroded sockets and cleaned the legs on 2 ROMs. Replaced damaged sockets on the Sync Bus Controller and VRAM Addresser modules. Recapped PCB and repaired burnt edge connector. Tested.
Title: Re: Midway Games
Post by: channelmaniac on November 27, 2020, 09:09:50 PM
Model: Pac Man
Symptom: Reboots

Cleaned CPU legs and recapped PCB. Tested.
Title: Re: Midway Games
Post by: channelmaniac on November 27, 2020, 09:12:24 PM
Model: Ms Pac Man (ROM Hack Pac Man)
Symptom: Crashes / Reboots

Board had solder clumped up on the edge connector.

Desoldered the edge connector and repaired burnt contacts on it. Tested to find it stuck in self-test reboot with "Memory OK." Cleaned the legs on the 6 Program ROMs and tested. Board played but the colors were off so that Ms Pac looked like a molded green wheel of cheese.  Cleaned the pins on the 74LS75 in the video output circuit and retested. Recapped the PCB and retested.
Title: Re: Midway Games
Post by: channelmaniac on November 28, 2020, 01:13:44 AM
Model: Super Ms Pac Man
Symptom: Dead. Garbage on screen

Game is a Ms Pac ROM hack using 2 extra ROMs and mods on the Pac Man board.

Someone had shoved the big square pins of the Sync Bus Controller and VRAM Addresser modules into the sockets on the main board, damaging them.

Cleaned legs on all 6 Program ROMs, recapped PCB, and repaired the edge connector. Game played, but Ms Pac looked like a wheel of green, moldy cheese. Cleaned dirty legs on the 74LS75 IC in the video output section and tested. Installed new sockets for the Sync Bus Controller and VRAM Addresser and installed sacrificial sockets on the pins on both modules. Reinstalled the modules and tested.
Title: Re: Midway Games
Post by: channelmaniac on December 09, 2020, 12:38:20 AM
Model: Galaxian
Symptom: Stuck in boot loop

Replaced bad ROM at position W and tested. Graphics were garbled. Replaced both character ROMs at 1H / 1J and tested. Rack sounds were off. Replaced the 2 transistors and the LM324 7T chip to fix those. Game would play but the rack sounds were incorrect at the end of the level. Found the 555 timer at 8T was installed backwards - and had factory solder. Removed chip, socketed the PCB, and reinstalled it in the correct orientation and successfully tested the rack sounds.
Title: Re: Midway Games
Post by: channelmaniac on December 09, 2020, 12:42:03 AM
Model: Ms Pac Man
Symptom: Dead, garbage on screen

Replaced bad mask ROM at 6H and tested. Recapped the audio and power sections of the PCB and retested.
Title: Re: Midway Games
Post by: channelmaniac on December 10, 2020, 04:00:36 PM
Model: Ms Pac Man
Symptom: No sound

Board had been recapped with radial caps and 1000uf were used instead of 10,000uf.

Replaced the radial caps with proper axial types. Replaced the audio amplifier IC to fix the missing audio issue. Board played but the moving characters were transparent - you could see the dots under them as they moved around the maze. Found a gouged trace causing the 6MHz signal to not make it to the 74LS75 in the video output section. Patched trace and retested.
Title: Re: Midway Games
Post by: channelmaniac on December 20, 2020, 11:57:18 PM
Model: Galaxian
Symptom: Deconvert from bootleg Pac Man

Removed several wire jumpers, reinserted multiple bent chip legs back into circuit, and patched multiple cut traces. Ran a test ROM to check memory while burning a whole ROM set - 5 program ROMs and 2 character ROMs. Installed the ROMs and tested.
Title: Re: Midway Games
Post by: channelmaniac on December 26, 2020, 07:10:35 PM
Model: Ms Pac Man
Symptom: Dead

Replaced bad ribbon cable socket on the daughterboard and put the 4 PAL chips back in the proper order (!!!!) - Tested.
Title: Re: Midway Games
Post by: channelmaniac on January 05, 2021, 11:15:51 PM
Model: Ms Pac Man
Symptom: Dead. Garbage on screen

Game was missing the ROM at 5F

Installed missing ROM. Replaced bad 74LS139 at 5L and bad RAM at 4M. Replaced damaged sockets on the two daugtherboards and the CPU. Tested. Recapped the PCB and tested again.
Title: Re: Midway Games
Post by: channelmaniac on February 03, 2021, 12:11:12 AM
Model: Pac Man
Symptom: Garbage on screen

Did not see garbage on screen. The PCB would try to boot then die. Clocks were failing.

Replaced bad socket on the 74LS107 in the clock section. Tested. Replaced volume pot to fix static noise in audio. Retested.
Title: Re: Midway Games
Post by: channelmaniac on February 14, 2021, 01:43:55 AM
Model: WWF Wrestlemania
Symptom: 10 Beeps

10 Beeps is a sound subsystem error. The screen showed an error after a few reboots of U86 being bad. A quick logic probe check revealed U86 and U80 were not getting +5v to pin 28. Replaced open SMT inductor at L1 and L7. Tested. Reprogrammed U129 to resolve a ROM error. Tested.
Title: Re: Midway Games
Post by: channelmaniac on February 14, 2021, 01:45:32 AM
Model: WWF Wrestlemania
Symptom: RAM Error

Board was skipping boot up diagnostics. Ran diagnostics by flipping DIP 1 and found an error with the 62256 SRAM at U37. Replaced the SRAM, removed a wire jumper from DIP SW 1, switch 2, and reprogrammed U129 to resolve a ROM error message. Tested.
Title: Re: Midway Games
Post by: channelmaniac on February 22, 2021, 11:36:31 PM
Model: Ms Pac Man
Symptom: Blows fuses

Replaced shorted zener diode and tested.
Title: Re: Midway Games
Post by: channelmaniac on February 23, 2021, 02:45:32 PM
Model: Ms Pac Man
Symptom: Crashes. Garbage on screen

Replaced bad Work RAM 1 at 4R and tested.
Title: Re: Midway Games
Post by: channelmaniac on February 23, 2021, 04:42:13 PM
Model: Pac Man
Symptom: Dead. Garbage on screen

Board had a 'Six Pac' enhancement kit installed.

Board would show a '0' on the screen along with some random garbage. Checked the RAMs and they were OK. Discovered a bent pin under the Z80 Sync Bus Controller. Fixed that and tested the board.
Title: Re: Midway Games
Post by: channelmaniac on April 02, 2021, 09:50:37 PM
Model: Ms Pac Man
Symptom: Dead. Garbage on screen.

Cleaned flaking silver tarnish off Mask ROMs and from inside sockets. Tested.
Title: Re: Midway Games
Post by: channelmaniac on April 02, 2021, 09:52:10 PM
Model: Ms Pac Man
Symptom: Dead. Missing parts.

Replaced missing voltage regulator and current pass transistors. Replaced bad 10uf cap in the zener diode circuit. Replaced one 2114 RAM with a broken leg and one bad 2114 RAM. Tested.
Title: Re: Midway Games
Post by: channelmaniac on June 30, 2021, 09:06:01 PM
Galaxian

Dead. Missing daughterboard.

Removed 2 EPROMs plugged in where the daughterboard goes. Installed replacement daughterboard and tested. "RAM 3 ERROR" - Replaced a bad 2101 RAM and tested. The game played but had sprite corruption. Checked the character ROMs at 1H / 1J and found that they both were the same ROM for 1H. Burned a replacement for 1J and tested.
Title: Re: Midway Games
Post by: channelmaniac on July 08, 2021, 06:58:07 AM
Model: Offroad Challenge
Symptom: Dead

Replaced physically damaged DSP chip and tested. Still dead. Checked the 4 program EPROMs and the sound program ROM, all were erased in poor storage. Reprogrammed the ROMs and tested.
Title: Re: Midway Games
Post by: channelmaniac on July 19, 2021, 07:56:36 PM
Model: Space Invaders Deluxe
Symptom: Crashes and reboots

Replaced 1 bad RAM and 3 ICs in the reset circuit to fix a glitch there. Tested.
Title: Re: Midway Games
Post by: channelmaniac on July 27, 2021, 02:54:59 PM
Model: Pac Man
Symptom: Dead

Repaired burnt edge connector and broken DIP switches and tested. Board was stuck in a boot loop. Replaced bad RAM and board booted but had no sound and horizontal lines through graphics. Repaired broken leg on ROM on row 5 to fix the graphics issue. Replaced bad LM377 audio amplifier IC to finish the repair. Tested.
Title: Re: Midway Games
Post by: channelmaniac on July 27, 2021, 02:55:34 PM
Model: Ms Pac Man
Symptom: Dead

Board was missing ribbon cable.

Cleaned solder globs on the edge connector. Replaced missing ribbon cable. Tested.
Title: Re: Midway Games
Post by: channelmaniac on August 12, 2021, 06:14:02 PM
Model: NBA Hangtime
Symptom: Corrupt graphics

Enabled self tests to see U10, U130, U123, and U112 errors. Reflowed the lifted corner of the RAM at U10 to fix that issue. Reprogrammed U130, U123, and U112 to fix the U112 error. Replaced the sockets for U130 and U123 to fix those errors and the remaining graphics issues.  Tested.
Title: Re: Midway Games
Post by: channelmaniac on August 15, 2021, 08:36:24 PM
Model: Rally-X
Symptom: No sprites

Replaced the three cables between the PCB. Replaced a 74LS157 and 74LS04 in the sprite RAM circuit. Fixed a bent pin on a custom chip. Tested.
Title: Re: Midway Games
Post by: channelmaniac on September 30, 2021, 09:30:37 PM
Model: Space Invaders
Symptom: Missing sounds

Replaced bad 4006 and 4030 ICs to fix the missile and base explosion sounds. Replaced bad 7417 chip to fix the missing thump sounds. Replaced 1uf cap and 39K resistor in the UFO sound circuit. Tested.
Title: Re: Midway Games
Post by: channelmaniac on September 30, 2021, 09:32:11 PM
Model: Space Invaders
Symptom: Missing sounds

Replaced bad 556 time to fix missing thump and low saucer sound issues. The output was stuck high on the 556 causing the output from the SN76477 to be overridden. Tested.
Title: Re: Midway Games
Post by: channelmaniac on September 30, 2021, 09:34:47 PM
Model: Space Invaders Deluxe
Symptom: Dead. Corrosion damage

Replaced corrosion damaged CPU socket and cleaned the CPU legs. Replaced corrosion damaged H and G ROMs and their sockets. Patched a dead corrosion damaged trace on data line D6 between G and H. Tested with a diagnostic ROM: Bad RAM at 8, B, and H. Replaced and socketed the three RAMs. Tested. Missing several sounds. Cleaned daughterboard finger contacts to fix the missing thump sounds. Replaced 5 LM3900 chips to fix all the missing sound issues. Tested.
Title: Re: Midway Games
Post by: channelmaniac on November 20, 2021, 02:46:28 PM
Model: Rally-X
Symptom: Dead. Missing Resistor Pack

Installed missing resistor pack. Cleaned dirt from board interconnects to fix missing /RESET signal on CPU. Removed, repaired, and reinstalled bent and shorting volume pot. Replaced bad 741 Op Amp and recapped the audio section to fix thumping oscillation in audio output. Replaced bad .1uf capacitor to fix explosion sounds. Tested.
Title: Re: Midway Games
Post by: channelmaniac on November 20, 2021, 02:58:20 PM
Model: NBA Jam Tournament Edition
Symptom: Graphic corruption

Players were missing at tip off for game. Game would randomly reboot and get stuck in a shot clock violation loop during attract mode. Test screen displayed a corrupt basketball court image on the lower half of the screen.

Reflowed UE13 and replaced a bad socket on UF5 to fix the reboot and shot clock issues. UF5 was the wrong type for the game. It was for the NBA Jam game, not tournament edition. Replaced the Tournament Edition ROMs with regular NBA Jam ROMs and the remaining graphics issues went away.
Title: Re: Midway Games
Post by: channelmaniac on December 14, 2021, 12:01:46 AM
Model: Ms Pac Man
Symptom: Randomly reboots

Replaced Sync Bus Controller socket and ROM sockets. Replaced ROM at 6F as it failed reprogramming. Fixed solder smear on parts side and a pin shorting to a trace on a RAM chip. Replaced a bad 74LS138 in the address decoding circuit as it was putting out 3v on the R/W signal trace from an input pin. Tested for 5 hours without a reboot.
Title: Re: Midway Games
Post by: channelmaniac on December 14, 2021, 12:04:44 AM
Model: Ms Pac Man
Symptom: Dead

Replaced missing crystal and cleaned ROM legs. Replaced corroded sacrificial sockets on the Sync Bus Controller and VRAM Addresser and their sockets on the board. Replaced the corroded CPU socket. Board would boot and pass diagnostics ROM, but would not boot the game. Replaced bad 74LS74 at 8C holding the /IRQ pin low. Retested. Replaced bad ribbon cable and tested game with daughterboard successfully. Recapped PCB and tested.
Title: Re: Midway Games
Post by: channelmaniac on December 31, 2021, 10:40:19 PM
Model: Mortal Kombat
Symptom: Garbage on screen.

Garbage was in a recognizable pattern. Removed a corroded dual-port video RAM, checked the traces under it, and replaced it. Fixed a smeared solder short on the bottom of the PCB. Straightened the pins on the bottom side of the PCB for the video RAM and now had a clear picture but a U99 error. Straightened pins on the graphics ROMs to fix that error. Straightened the pins for the sound board connectors and the kick harness connector. Cleaned and recapped the sound PCB. Replaced an electrolyte corrosion damaged audio amp chip and a missing crystal. Tested.
Title: Re: Midway Games
Post by: channelmaniac on February 20, 2022, 09:21:00 PM
Model: Mortal Kombat II
Symptom: Test and repair board

Board had a burned +5v contact on the edge connector. Repaired. Replaced corroded P5 connector for the kick harness. Powered up game to find 2 bongs from the sound board. Replaced bad ROM U2 and corroded socket. Recapped the sound PCB as the radial caps were leaking on the PCB and the axial ones are known for drying out and causing scratchy noises. Tested. Board would sometimes jump straight to Game Over when start is pressed. Cleaned the grungy legs on the UG12/UJ12 Program ROMs, reseated the CPU and PLCC custom IC. Reflowed the custom DMA controller at UE13 and replaced its four filter caps. Tested.
Title: Re: Midway Games
Post by: channelmaniac on March 14, 2022, 07:49:59 PM
Model: NBA Jam TE
Symptom: Corrupt graphics

Straightened bent pins on the bottom of the PCB, replaced a bad 84 pin PLCC socket on a custom chip, and tested. Two ROMs showed as bad. Swapped the two incorrectly installed ROMs and retested successfully.
Title: Re: Midway Games
Post by: channelmaniac on March 21, 2022, 06:58:48 PM
Model: Total Carnage
Symptom: Crackly sound

Recapped sound PCB and tested.
Title: Re: Midway Games
Post by: channelmaniac on April 30, 2022, 10:06:17 PM
Model: Pac Man (modified)
Symptom: Dead

Board was missing the 2 daughter cards and was hacked with a single ROM and 2 switches to go between normal / fast and Pac / Ms Pac.

Installed missing daughterboards and tested. Board would try to boot and fail with a single 0 on the screen. Replaced bad Z80 CPU and tested.
Title: Re: Midway Games
Post by: channelmaniac on May 15, 2022, 10:35:16 PM
Model: Ms Pac man
Symptom: Damaged edge connector.

Removed all the crumpled up copper foil and cleaned the edge connector. Installed copper trace tape to patch the edge connector and tested. Replaced bad ROM at 5F. Tested. Replaced bad ribbon cable. Tested. Fixed broken solder joint on the Sync Bus Controller module to fix a crashing issue.  Replaced bad socket on the VRAM Addresser module and the socket for it on the PCB to fix video corruption. Replaced bad audio amplifier IC to fix missing audio. Tested.
Title: Re: Midway Games
Post by: channelmaniac on August 09, 2022, 08:43:55 PM
Model: Space Invaders
Symptom: Dead

Replaced shorted 10uf tantalum cap on the 12v line under the heatsink on the sound PCB. Tested - missing sounds except Saucer and background bass. Replaced 6 LM3900 chips and 2 560K resistors. Tested.
Title: Re: Midway Games
Post by: channelmaniac on August 09, 2022, 11:56:25 PM
Model: Space Invaders Deluxe
Symptom: Missing sounds. Problems with 2 player game

Daughter board had a note about loose edge connection contacts. Epoxied loose contacts back to the PCB. Replaced 5 LM3900 chips to fix sound issues. Unit would start a 2 player game but fire button would not work. Replaced bad DIP Switch bank. Switch 5 was open. Tested.
Title: Re: Midway Games
Post by: channelmaniac on August 10, 2022, 09:53:33 PM
Model: Space Invaders
Symptom: Dead

Cleaned pins on the daughter board. Replaced bad CPU and 4 mask ROMs that suffered from pin rot. Tested.
Title: Re: Midway Games
Post by: channelmaniac on August 11, 2022, 01:52:34 PM
Model: Space Invaders
Symptom: Dead

Replaced bad CPU and tested. Replaced LM3900 at M5 to fix a missing Invader Hit sound effect. Tested.
Title: Re: Midway Games
Post by: channelmaniac on August 11, 2022, 10:58:26 PM
Model: Space Invaders
Symptom: Dead

Replaced bad CPU. Replaced 4 resistors, 2 caps, and 1 SN76477 to return the mothership sound to working order. Replaced a physically broken cap to fix the missile fire sound. Tested.
Title: Re: Midway Games
Post by: channelmaniac on August 15, 2022, 03:09:42 PM
Model: Sea Wolf
Symptom: Dead

Replaced bad 74S04 to restore main clock. Replaced bad 9320 clock divider to restore the rest of the clocking signals. Replaced bad 7414 at D1 on the daughter board holding reset stuck. Replaced bad ROM socket causing graphic corruption. Replaced shorted 7414 at C1 on the turret input circuit. Replaced a bad 7417 IC and 4401 transistor on the daughterboard in the light control circuit. Replaced bad 7406 in the sound control circuit on the daughterboard.
Title: Re: Midway Games
Post by: channelmaniac on August 15, 2022, 03:12:56 PM
Model: Ms Pac Man
Symptom: Dead. Garbage on screen.

Reset circuit was stuck low. Replaced shorted transistor at Q3, shorted diode at D2; bad 74LS161 with shorts on pins 7, 9, and 10 at 9C; and replaced a 74LS08 with a shorted input pin at 7H. Tested.
Title: Re: Midway Games
Post by: channelmaniac on October 18, 2022, 06:03:14 PM
Model: Ms Pac Man
Symptom: Dead. Nothing on screen

Replaced bad clock divider at 3S and tested.
Title: Re: Midway Games
Post by: channelmaniac on October 18, 2022, 06:03:37 PM
Model: Ms Pac Man
Symptom: Dead, garbage on screen

Replaced bad CPU socket and tested.
Title: Re: Midway Games
Post by: channelmaniac on October 26, 2022, 10:05:08 PM
Model: Ms Pac Man
Symptom: Dead

Replaced the sockets for the Sync Bus Controller and VRAM Addresser. Cleaned the pins on the Sync Bus Controller module then installed both and the zip ties to hold them in place. Tested.
Title: Re: Midway Games
Post by: channelmaniac on November 20, 2022, 09:43:14 PM
Model: Demolition Derby
Symptom: No audio

Tested main PCB and sound board OK. Had customer send in the amplifier PCB. Replaced 3 bad caps on the amplifier PCB and checked the solder joints on the connectors and audio amp ICs. Tested.
Title: Re: Midway Games
Post by: channelmaniac on November 23, 2022, 12:19:03 AM
Model: The Grid
Symptom: Wave RAM errors

Reflowed Wave RAM and tested. Replaced 3 EPROMs giving errors on self test. Replaced corroded R322 and burned coil on pin 2 of the Player 3 Controls port. Installed three missing standoffs to help keep the board from flexing when it gets reinstalled.
Title: Re: Midway Games
Post by: channelmaniac on November 23, 2022, 12:20:53 AM
Model: The Grid
Symptom: Dead. Missing parts.

Installed missing screw, nut, and insulator on the 3.3v regulator. Found the Security PIC was dead. Replaced with one from the other board the customer sent in and the board sprang to life. Replaced 3 EPROMs giving errors during self test. Reflowed one side of the ADSP-2104 and tested audio. Board now passed tests but had corrupt graphics. Reflowed the PFQP Wave RAM and tested. Installed 5 missing standoffs.
Title: Re: Midway Games
Post by: channelmaniac on December 01, 2022, 11:49:31 PM
Model: Mortal Kombat 3
Symptom: Dead

Board wasn't dead... played blind.

Replaced shorted U91 and U75 and one 74ALS541 in the video output. This restored sync and a short burst of video during the Palette RAM test. Replaced U45 to get video to return. Replaced both Palette RAMs and the Orbit chip to fix Palette RAM errors. Replaced U33 to fix a U33 error after a reflow did not fix the issue. Tested.
Title: Re: Midway Games
Post by: channelmaniac on December 03, 2022, 01:46:51 PM
Model: Ms Pac Man
Symptom: Dead. Flashing 0s on screen

Replaced all 6 2114 RAM chips and tested. One was bad, but the other five had disintegrating legs (rusted silver plated steel legs) so all were replaced to make the board more stable.
Title: Re: Midway Games
Post by: channelmaniac on December 13, 2022, 02:29:59 AM
Model: Mortal Kombat 3
Symptom: Player 2 up and down not working

Replaced bad 74HCT541 chip and tested.
Title: Re: Midway Games
Post by: channelmaniac on December 13, 2022, 02:30:41 AM
Model: Mortal Kombat II
Symptom: Graphics corruption and reboots during attract mode

Reflowed UE13 and replaced the 4 monolithic capacitors around it.
Title: Re: Midway Games
Post by: channelmaniac on January 06, 2023, 08:22:13 PM
Model: WWF
Symptom: U33 error, garbage on screen

Board had a missing edge connector contact finger.

Reflowed U33 and patched a dead trace to fix the error. Cleaned up the battery socket and replaced the dead battery to fix a CMOS settings error. Used high-temp 2-part epoxy to affix a replacement edge connector finger contact and soldered it into the circuit. Tested.
Title: Re: Midway Games
Post by: channelmaniac on January 30, 2023, 01:15:40 AM
Model: Bosconian
Symptom: Sprite issues then many chips with broken legs after owner reseated chips.

Replaced all the 24/28/40/42 pin sockets and the unencapsulated resistor packs. Replaced ROMs with multiple broken legs at 3J on CPU board and 4D, 5L, 5M, and 5N on video board. Repaired broken leg on the 05xx and 50xx chips on the video PCB. Replaced 08xx chips at 2E and 2H as they had too many broken legs to repair. Repaired broken pins on chips at 3L, 3K, and 4H (51xx custom) on the CPU board. Tested.
Title: Re: Midway Games
Post by: channelmaniac on February 16, 2023, 07:45:31 PM
Model: WWF Wrestlemania
Symptom: Sound subsystem failure

A RAM was badly replaced as an attempted repair.

Replaced 2 open SMT coils on the sound RAMs. Removed the RAM and found Pin 6, Pin 11, and Pin 21 had broken connections. Installed a socket and patched the three traces. Tested.
Title: Re: Midway Games
Post by: channelmaniac on February 16, 2023, 09:48:37 PM
Model: Mortal Kombat II
Symptom: Dead

Corroded pins on 2 ROMs

Replaced UJ22 and UJ23 ROMs and their sockets. Replaced corroded DSP CPU's PLCC socket and cleaned the chip's legs. Tested.
Title: Re: Midway Games
Post by: channelmaniac on February 23, 2023, 01:23:05 PM
Model: NBA Jam TE
Symptom: No sound

Missing reset. Replaced bad 74LS14. Now has power on reset but not reset when moving through configuration menus. Replaced bad 74LS11 in the reset circuit. No clock to Oki 6295 sample playback. Replaced bad 74LS74 with a shorted output. Address decoding not working properly so replaced bad 74LS138. Address banking on Program ROM not working Replaced 74LS139. Now had power on bong and music but no sample playback. Replaced OKI 6295 chip and tested.
Title: Re: Midway Games
Post by: channelmaniac on February 23, 2023, 01:25:45 PM
Model: Mortal Kombat
Symptom: No sound

CPU would not start. Found a short of 105.4 ohms on the data bus. Replaced bad TLC7524 DAC. Address decoding was not working as /DAC signal was missing. Replaced 74LS138 and board appeared to boot but had no sound outputs. Replaced bad YM2151 to get music. Replaced shorted LM324 to get power on bong soudn back. Fixed bent power pin on ROM U13. Noticed U12 and U13 were in wrong locations and swapped them. No audio samples. Replaced OKI6295 and tested. Replaced bad U13 audio sample ROM. Tested.
Title: Re: Midway Games
Post by: channelmaniac on March 08, 2023, 10:38:48 PM
Model: Ms Pac Man
Symptom: Reboot loop

Board was rebooting after completing self tests when starting to display attract mode. Removed ROMs on row 6, cleaned pins on two ROMs and reinserted them. Tested.
Title: Re: Midway Games
Post by: channelmaniac on March 08, 2023, 10:40:19 PM
Model: NBA Jam
Symptom: Hot ROMs on sound board

U12 and U13 were in circuit backwards. Programmed two replacement ROMs and installed them. Audio was very faint and distorted. Added a 3rd wire to customer's volume pot cable and tested.

Note: MK II uses 2 wires to the pot while NBA Jam requires the third wire.
Title: Re: Midway Games
Post by: channelmaniac on March 08, 2023, 10:42:17 PM
Model: NBA Jam Tournament Edition
Symptom: Upgrade ROMs to Rewind Edition (Jordan)

Removed 16 ROMs and installed customer supplied ROMs. Added a third wire to customer's volume pot cable and tested. Very low audio unless pot is in the middle of its arc. The two factory pins on the wire harness went to the wrong volume pot terminals. Swapped the wires and audio was fixed. Tested.
Title: Re: Midway Games
Post by: channelmaniac on March 09, 2023, 02:15:09 AM
Model: Ms Pac Man w/Super Pac Gal hack
Symptom: Scrambled screen

Replaced bad RAMs at 4L and 4N. Moved a mod wire from pin 19 to pin 20 on the ROM and tested. Repaired burned edge connector. Tested.
Title: Re: Midway Games
Post by: channelmaniac on March 09, 2023, 02:16:07 AM
Model: Ms Pac Man
Symptom: Scrambled screen

Replaced sacrificial sockets on the Z80 Sync Bus Controller and VRAM Addresser modules. Replaced motherboard socket for the VRAM Addresser. Tested.
Title: Re: Midway Games
Post by: channelmaniac on March 09, 2023, 02:16:37 AM
Model: Ms Pac Man
Symptom: Scrambled screen

Replaced bad RAM at 4K and tested
Title: Re: Midway Games
Post by: channelmaniac on March 09, 2023, 02:17:29 AM
Model: Ms Pac Man
Symptom: Scrambled screen

Replaced 74LS161 at 9C to fix a stuck /RESET line. Tested.
Title: Re: Midway Games
Post by: channelmaniac on March 09, 2023, 02:18:31 AM
Model: Ms Pac Man
Symptom: No sync

Replaced 74LS161 chips at 2R and 2S. Replaced the Z80 Sync Bus socket and sacrificial socket. Tested to find sputtering low audio. Replaced audio amplifier IC and tested.
Title: Re: Midway Games
Post by: channelmaniac on March 10, 2023, 03:45:06 PM
Model: MK4
Symptom: Dead

Board had a burnt tantalum on the -5v line.

Board made buzzing sounds that regularly changed, like the CPU was running attract mode. Cranked up the video brightness on monitor and reset the CPU to see tiny streaks of colors on the far right wiping down the screen - test mode was running. Replaced the audio op amp, the video amp IC, and the burnt 10uf tantalum cap. Tested.

Player 2 Button 2 failed to register. Found the custom IC 5410-14589-00 had a shorted input to +5v. Replaced the custom IC with one from a parts board and tested.
Title: Re: Midway Games
Post by: channelmaniac on March 21, 2023, 06:55:41 PM
Model: Galaga
Symptom: Garbage on screen

Replaced all 24/28/40/42 pin sockets and unencapsulated resistor packs. Tested.
Title: Re: Midway Games
Post by: channelmaniac on March 21, 2023, 06:56:00 PM
Model: Galaga
Symptom: Garbage on screen

Replaced all 24/28/40/42 pin sockets and unencapsulated resistor packs. Tested. Replaced 06xx chip and retested.
Title: Re: Midway Games
Post by: channelmaniac on March 30, 2023, 11:25:04 AM
Model: Galaga
Symptom: Garbage on screen.

Replaced all 24/28/40/42 pin sockets and unencapsulated resistor packs. Tested. Replaced 2 leaking filter capacitors and retested.
Title: Re: Midway Games
Post by: channelmaniac on May 17, 2023, 03:18:29 PM
Model: Ms Pac Man
Symptom: Lines on screen

Cleaned legs of Character ROM at 5E. Tested.
Title: Re: Midway Games
Post by: channelmaniac on May 17, 2023, 03:20:38 PM
Model: Ms Pac Man
Symptom: Dead. Garbage on screen

Replaced bad 74LS161 at 3R. Replaced all 6 corroded RAM chips. Cleaned ROM legs of the 4 program ROMs at row 6. Board would crash intermittently. Replaced bad socket on the Z80 Sync Bus Controller. Cleaned CPU legs. Board would boot and play but the orange ghost would rapidly move all around the screen. Cleaned the ROM legs on the daughter board and tested.
Title: Re: Midway Games
Post by: channelmaniac on June 02, 2023, 11:08:49 PM
Model: Ms Pac Man
Symptom: Crashing

Rebuilt ground connection on the edge connector and heat soak tested.
Title: Re: Midway Games
Post by: channelmaniac on June 02, 2023, 11:09:28 PM
Model: Ms Pac Man
Symptom: No sounds, just popping noises

Replaced dead 74LS174 in the sound circuit. Game would randomly crash. Replaced bad ribbon cable and tested.
Title: Re: Midway Games
Post by: channelmaniac on June 02, 2023, 11:36:11 PM
Model: Galaga
Symptom: Will not run

Board had a broken program ROM and had many chips already in machine pin sockets.

Replaced broken Program ROM. Replaced 2 Z80 CPU sockets, the 51xx socket, and the three 8xx sockets on the CPU board. Replaced 2 character ROM sockets, the 02xx socket, the 2016 SRAM socket, and the 00xx socket on the video PCB. Replaced the 470uf filter caps on each PCB. Tested.
Title: Re: Midway Games
Post by: channelmaniac on August 08, 2023, 09:56:13 PM
Model: Galaga
Symptom: Random errors

Replaced all 24/28/40/42 pin sockets and unencapsulated resistor packs. Tested.
Title: Re: Midway Games
Post by: channelmaniac on August 08, 2023, 09:56:57 PM
Model: Galaga
Symptom: Dead

Replaced all 24/28/40/42 pin sockets and unencapsulated resistor packs. Replaced radial audio and reset caps with proper axial caps. Tested. White screen. Replaced bad ROM 4 and retested.
Title: Re: Midway Games
Post by: channelmaniac on August 10, 2023, 07:25:56 PM
Model: Galaga
Symptom: Dead

Replaced all 24/28/40/42 pin single wipe sockets and unencapsulated resistor packs. Soldered one 08xx with multiple broken pins into a machine pin socket to salvage it. Tested.
Title: Re: Midway Games
Post by: channelmaniac on August 10, 2023, 07:27:23 PM
Model: Galaga
Symptom: Dead

Replaced all 24/28/40/42 pin single wipe sockets and unencapsulated resistor packs. Soldered the 05xx starfield generator chip with multiple broken pins into a machine pin socket to salvage it. Tested. RAM error. Replaced bad 08xx on CPU 3 and tested. Graphics glitch with repeating character slices, but with OK text. Replaced bad 74LS86 at 4C with a racing output on pin 8 and tested.
Title: Re: Midway Games
Post by: channelmaniac on August 11, 2023, 11:29:28 PM
Model: Galaga
Symptom: Random crashes and reboots

Board would show doubled up text on the screen, both horizontally and vertically.

Found address bus AB5 signal on the far side of the 74LS367 chips shorted to ground by 113 ohms. Replaced bad 74LS138 at 1P and tested.
Title: Re: Midway Games
Post by: channelmaniac on August 30, 2023, 03:26:51 AM
Model: Galaga
Symptom: Dead. Garbage on screen

Board was missing resistor pack in the sound section and the Program ROMs were all mixed up in their sockets.

Replaced all 24/28/40/42 pin single wipe sockets and unencapsulated resistor packs. Replaced incorrect radial caps with axial caps. Replaced 50-pin CPU board interconnect socket. Put the program ROMs back into their proper sockets. Board booted to the explosion sound and RAM OK. Checked the ROMs for CPU 2 and CPU 3. Replaced bad ROM at location 3E for CPU 3. Tested. Missing motion sprites. Reseated PROM at 1C and retested.
Title: Re: Midway Games
Post by: channelmaniac on September 18, 2023, 01:03:30 AM
Model: Mortal Kombat II
Symptom: Error in UE13

Reflowed IC at UE13 and tested.
Title: Re: Midway Games
Post by: channelmaniac on September 18, 2023, 01:04:50 AM
Model: Mortal Kombat II
Symptom: Loud piercing audio output

Removed J6 to isolate the digital side and DAC. Sound persisted. Removed C106 and sound disappeared. Replaced bad TL074 OpAmp and replaced 5 radial capacitors. Tested.
Title: Re: Midway Games
Post by: channelmaniac on September 20, 2023, 11:38:40 PM
Model: Mortal Kombat II
Symptom: Dead. Missing RAM chip.

Replaced missing 44256 DRAM chip and patched a damaged trace. Tested. Board was dead. Replaced damaged DSP CPU socket and tested. Repaired bent pins on sound connector and tested with sound board.
Title: Re: Midway Games
Post by: channelmaniac on September 20, 2023, 11:39:10 PM
Model: Mortal Kombat II
Symptom: Sputtering sound

Recapped sound PCB and tested.
Title: Re: Midway Games
Post by: channelmaniac on September 20, 2023, 11:39:48 PM
Model: Mortal Kombat II
Symptom: Sputtering sound

Recapped sound PCB, resoldered audio amp chip, straightened bent pins on the ribbon cable connector, and tested.
Title: Re: Midway Games
Post by: channelmaniac on September 21, 2023, 11:47:52 PM
Model: Mortal Kombat II
Symptom: Dead. Missing RAM chip

Replaced missing 44256 RAM chip and patched a damaged trace. Straightened bent pins on multiple connectors. Tested. Game started and immediately went to Game Over. Reflowed UE13 (Custom DMA Controller IC) and retested.
Title: Re: Midway Games
Post by: channelmaniac on September 21, 2023, 11:49:44 PM
Model: Mortal Kombat II
Symptom: Dead: Missing ROMs. Labeled "Bad UE13"

Replaced 2 missing ROMs with programmed EPROMs. Would not boot. Replaced damaged DSP CPU Socket and tested. UE13 failure. Reflowed UE13 (Custom DMA Controller) chip as it had visibly broken solder joints on multiple pins. Retested. Straightened multiple bent pins on connectors and replaced a broken pin for Coin 3. Tested.
Title: Re: Midway Games
Post by: channelmaniac on September 21, 2023, 11:50:34 PM
Model: Mortal Kombat "T-Unit"
Symptom: UG22 error

Replaced missing UG22 ROM chip. Straightened multiple bent connector pins. Tested.
Title: Re: Midway Games
Post by: channelmaniac on November 04, 2023, 03:44:09 PM
Model: Mortal Kombat II sound board
Symptom: Missing parts

Replaced 3 missing ROMs and reprogrammed the 3 existing ROMs as they suffered bit rot. Recapped the PCB. Installed a missing audio amplifier chip and heatsink. Tested.
Title: Re: Midway Games
Post by: channelmaniac on November 27, 2023, 08:29:49 PM
Model: NBA Jam Sound PCB
Symptom: Dead

Replaced 32 pin socket on U3 and replaced bad U3 that failed checksum tests on the programmer. Replaced broken sockets on the YM2151 and the YM3012 DAC. Repaired a dead trace on the 74LS138 decoder and one between the CPU and the ROM at U3. Now the board would give 3 beeps during diagnostics indicating a bad U3. Patched a dead trace on the 74LS138 to the data latch handling the upper memory paging of the ROM at U3. Board now passes all tests and plays properly.
Title: Re: Midway Games
Post by: channelmaniac on November 27, 2023, 11:38:47 PM
Model: NBA Jam Sound PCB
Symptom: Dead

Replaced bad 24 pin socket on the YM2151 chip. Replaced bad 6264 SRAM chip and tested.
Title: Re: Midway Games
Post by: channelmaniac on December 05, 2023, 03:18:19 AM
Model: NBA Jam Sound PCB
Symptom: Dead. Convert to Mortal Kombat

Replaced broken 3.579MHz crystal and missing main filter cap. Replaced U3, U12, and U13 EPROMs with ones programmed for Mortal Kombat. Board played, but sounded fuzzy and distorted. Recapped PCB and retested successfully.
Title: Re: Midway Games
Post by: channelmaniac on December 11, 2023, 07:01:46 PM
Model: Mortal Kombat II sound PCB
Symptom: Please rebuild

Recapped the PCB and cleaned under the 2200uf cap as it was leaking. Tested.
Title: Re: Midway Games
Post by: channelmaniac on December 12, 2023, 07:58:09 PM
Model: Galaga
Symptom: Stuck on white screen

Board had a rebuild kit installed by owner.

Replaced bad 2k x 8 SRAM on the video PCB. Removed multiple shorted pad to trace solder blobs on the CPU board. Patched a dead trace between the 08xx chips for CPU 1 and CPU 2 (pin 26 to pin 15) and tested.
Title: Re: Midway Games
Post by: channelmaniac on December 15, 2023, 10:01:01 PM
Model: Space Invaders
Symptom: Dead, lines on screen

Replaced program ROMs with freshly programmed EPROMs and tested.
Title: Re: Midway Games
Post by: channelmaniac on December 15, 2023, 10:01:40 PM
Model: Space Invaders
Symptom: Dead, lines on screen

ROM F had broken legs. Replaced all 4 program ROMs with freshly programmed EPROMs and tested.
Title: Re: Midway Games
Post by: channelmaniac on December 16, 2023, 04:27:53 PM
Model: Open Ice
Symptom: Sound subsystem error

Reprogrammed Sound ROM U4. Tested.
Title: Re: Midway Games
Post by: channelmaniac on December 20, 2023, 02:15:30 PM
Model: Revolution X
Symptom: Graphics errors and memory failure messages on self-test

Removed, cleaned, and recapped the logic board. Patched 3 dead traces caused by SMT capacitor electrolyte leakage. Board still showed errors in the dual-port video RAM, the Palette RAM, and a security chip failure not caused by dead traces. Replaced the 74ABT245 at U17 to fix the Palette RAM and security chip issues. Replaced the 74ABT244 chip just to the left of the large PLCC custom to fix the Dual-Port video RAM errors.
Title: Re: Midway Games
Post by: channelmaniac on December 20, 2023, 02:17:25 PM
Model: Revolution X
Symptom: Error with chip U122

Replaced the bad ROM with a 27C040 EPROM and tested.
Title: Re: Midway Games
Post by: channelmaniac on December 20, 2023, 02:20:06 PM
Model: Revolution X Sound PCB
Symptom: Dead

Replaced bad ROM at U2 and sockets for U2 and U9. Replaced bad 74HC541 at U22 to restore the /OE signal to the ROMs.  Board would intermittently boot to 2 bongs. Replaced 74ALS245 at U24. Replaced bad 74HC174 with stuck outputs. Board would repeatedly boot to 2 bongs. Replaced bad 74HC541 at U23. Tested. Recapped the PCB and retested.
Title: Re: Midway Games
Post by: channelmaniac on December 20, 2023, 10:34:46 PM
Model: Revolution X Sound PCB
Symptom: Dead

Stuck in Reset. Replaced the RS-232 driver chips and tested. Board was dead. Oscilloscope captured an extremely brief pulse of activity before the board died. Replaced the 74HC541 at U23 and tested. Recapped the board. Tested.
Title: Re: Midway Games
Post by: channelmaniac on December 20, 2023, 11:44:05 PM
Model: Revolution X Sound PCB
Symptom: Dead

Board had some odd liquid spill damage

Replaced the PLCC socket for the DSP chip, the pin header for the ribbon cable, and the 24 pin socket for the GAL. Replaced bad 74HC541 chips at U21 and U22 that had stuck outputs. Recapped PCB and tested.
Title: Re: Midway Games
Post by: channelmaniac on December 21, 2023, 01:33:47 AM
Model: Revolution X
Symptom: Jailbars on screen. Fails video RAM tests.

Board had a lot of attempted repair work done already.

Found Address A1 stuck high on every dual-port video RAM chip. Traced it backwards through the schematic and found a corroded trace next to surface mount capacitor C18. Patched the trace and tested.
Title: Re: Midway Games
Post by: channelmaniac on December 23, 2023, 12:14:16 AM
Model: Revolution X
Symptom: Recap and clean residue

Remove all the surface mount capacitor from the PCB, prepped and cleaned pads, and installed new capacitors. Tested.
Title: Re: Midway Games
Post by: channelmaniac on December 23, 2023, 12:21:27 AM
Model: Ultimate Mortal Kombat 3
Symptom: No sound

Verified that the sound data was getting to the CAC. Cleaned residue off the SMT parts next to the sound DAC, replaced a bad 100 ohm SMT resistor, patched a corroded trace, a TL084 OpAmp, and replaced the Audio Amp IC. Tested.
Title: Re: Midway Games
Post by: channelmaniac on December 23, 2023, 12:23:11 AM
Model: Space Invaders Deluxe
Symptom: Dead. Stuck in watchdog.

Replaced bad RAM 5 (Location G12) and tested.
Title: Re: Midway Games
Post by: channelmaniac on January 04, 2024, 06:44:54 PM
Model: Revolution X Sound board
Symptom: Dead

Board had attempted repairs done.

Reflowed the blobbed solder on the bridge rectifier and patched a dead trace from the low voltage AC power connector to the bridge. Recapped the PCB except for the large filter cap. Replaced 3 1.5uf bipolar caps with the proper .1uf caps. Desoldered and reinstalled the audio amp IC so the heatsink would properly fit. Installed one missing screw/nut on the heat sink. Resoldered the cracked connections on the large filter cap to fix AC buzzing noise. Replaced dead IC23 and tested.
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