Author Topic: Midway Games (Read 107175 times)

channelmaniac · « **Reply #120 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.

channelmaniac · « **Reply #121 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.

channelmaniac · « **Reply #122 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.

channelmaniac · « **Reply #123 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.

channelmaniac · « **Reply #124 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.

channelmaniac · « **Reply #125 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.

channelmaniac · « **Reply #126 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.

channelmaniac · « **Reply #127 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.

channelmaniac · « **Reply #128 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

channelmaniac · « **Reply #129 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.

channelmaniac · « **Reply #130 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.

channelmaniac · « **Reply #131 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.

channelmaniac · « **Reply #132 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.

channelmaniac · « **Reply #133 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.

channelmaniac · « **Reply #134 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.

channelmaniac · « **Reply #135 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.

channelmaniac · « **Reply #136 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.

channelmaniac · « **Reply #137 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.

channelmaniac · « **Reply #138 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.

channelmaniac · « **Reply #139 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.

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Author Topic: Midway Games (Read 107175 times)