NLG Users Repair Logs and Other Ramblings. Request your very own topic. Just ask any site staff. > Channelmaniac's Arcadecomponents' Old School Repair Logs

Midway Games

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channelmaniac:
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.

channelmaniac:
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.

channelmaniac:
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.

channelmaniac:
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.

channelmaniac:
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.

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