Author Topic: Midway Games (Read 102613 times)

channelmaniac · « **Reply #280 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.

channelmaniac · « **Reply #281 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.

channelmaniac · « **Reply #282 on:** September 22, 2018, 10:46:28 AM »

Model: Mortal Kombat II
Symptom: Graphics corruption

Reflowed the custom DMA chip at UE13 and tested.

channelmaniac · « **Reply #283 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.

channelmaniac · « **Reply #284 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.

channelmaniac · « **Reply #285 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.

channelmaniac · « **Reply #286 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.

channelmaniac · « **Reply #287 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.

channelmaniac · « **Reply #288 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.

channelmaniac · « **Reply #289 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.

channelmaniac · « **Reply #290 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.

channelmaniac · « **Reply #291 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.

channelmaniac · « **Reply #292 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.

channelmaniac · « **Reply #293 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.

channelmaniac · « **Reply #294 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.

channelmaniac · « **Reply #295 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.

channelmaniac · « **Reply #296 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.

channelmaniac · « **Reply #297 on:** May 07, 2019, 09:26:32 PM »

Model: Ms Pac Man
Symptom: Split screens

Replaced bad 74LS161 clock divider chip and tested.

channelmaniac · « **Reply #298 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.

channelmaniac · « **Reply #299 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.

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Author Topic: Midway Games (Read 102613 times)