Ms Pacman Repair Logs

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Repairer: channelmaniac

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.


Symptom: Rebooting at random

Replaced the CPU socket and socket J1 for the ribbon cable on the daughterboard.


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.


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.



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.


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.


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.


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.


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.


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.


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.


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.


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.


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.


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.


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.


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.