Midway Games

[channelmaniac]

Model: Space Invaders
Symptom: No sound

Board arrived dead. Replaced bad RAM at H6 and tested. Board had some sounds, but not all. Replaced the LM3900 chips at M4 and P4 to restore the Missile sound. Replaced LM3900 at K3-4 to restore the explosion sound. Replaced the LM3900 chips at K4 and K5 to restore the invader hit sound. Tested.

[channelmaniac]

Model: Galaga
Symptom: Dead. Garbage on screen

Replaced all the 24/28/40/42 pin sockets. Resistor packs were of the OK type. Tested. Replaced bad RAM at 1K on the video PCB. Tested.

[channelmaniac]

Model: Galaga
Symptom: Missing parts. Rebuild.

Board had attempted repair damage.

Replaced all the 24/28/40/42 pin sockets. Replaced 3 resistor packs that were made of individual resistors. Removed all 8 2147 RAM chips and replaced them with 2 2148 RAMs. Tested. Board would boot and play but had no sprites, just empty boxes on the screen. PROM at 1C had no outputs. Worked backwards in the circuit to the LS377 @ 2D. Clock was making it to pin 11's solder pad, but not to the top of the leg. The leg had been cut and not fully soldered back together by a previous tech. Removed the IC, installed a socket, and installed a replacement LS377. Tested.

[channelmaniac]

Model: Galaga
Symptom: White screen

Replaced all the 24/28/40/42 pin single wipe sockets and unencapsulated resistor packs. Tested. Replaced 2 bad Z80 CPUs. Tested.

[channelmaniac]

Model: Galaga
Symptom: Random RAM errors

Replaced all the 24/28/40/42 pin single wipe sockets and unencapsulated resistor packs. Tested.

[channelmaniac]

Model: Galaga
Symptom: Striped sprites with color issues

Removed the 8x 2147 Fast RAM from the board. One tested bad. Installed 2x 2148 chips as this customer puts thousands of hours on his games and these will pull less power and run cooler. Tested.

[channelmaniac]

Model: Ultimate Mortal Kombat III
Symptom: Missing colors on output. No sound.

Board suffered shipping damage causing these issues.

Replaced cracked 74ALS541 chip in the video output section. Replaced cracked 470 ohm isolated resistor pack. Tested. Sound cable was plugged in backwards on the sound PCB. Plugged cable in correctly and the sound fully returned. Tested. DIP switches were not working. Replaced both banks of switches and tested. Cleaned edge connector pin for Player 1 Button 3 and retested.

[channelmaniac]

Model: Ms Pac Man
Symptom: Dead

Repaired damaged edge connector. CPU was missing clock and Sync Bus Controller was loose in socket. Replaced CPU socket, Sync Bus Controller socket, and sacrificial socket on Controller. Zip tied module into place properly and tested.

[channelmaniac]

Model: Revolution X
Symptom: Sound board clicks and repeats sounds

Main logic board complained of the sound revision being too low and was sending out reset pulses to the sound board. Downgraded the board from Rev 1.0 to Proto 5 to fix issue. Sound board was recapped and tested.

[channelmaniac]

Model: Revolution X
Symptom: Random self test failures and crashing. No sound.

Recapped the PCB and patched multiple dead traces. Replaced corrosion damaged 47 ohm resistor R79 on the output of U29 supplying the ALTCH signal, a.k.a. Address Latch signal. This was causing the signal to randomly cut out to where the address lines could not be latched out of the combined address and data bus.

Recapped the audio PCB and replaced 2 bad 74HC541 chips. Tested.

[channelmaniac]

Model: Mortal Kombat
Symptom: Dead

"Board reported 'searching for scratch RAM' before dying"

Socketed and tested Scratch RAM. Found corrosion on the edge connector and green socket contacts for the custom logic at U65. Replaced socket and tested. No green output. Cleaned and retinned the green and sync edge connections and tested.

[channelmaniac]

Model: Mortal Kombat Sound PCB
Symptom: Makes noise. Install cust supplied cap kit

Installed cap kit. Replaced C71 (470pf) cap in the feedback circuit on U33 between pins 1 and 2. Tested

[channelmaniac]

Model: Mortal Kombat 2 sound PCB
Symptom: Recap and test

Recapped the PCB and tested.

[channelmaniac]

Model: MK II sound PCB
Symptom: 10 Bongs

Board had been recapped.

10 Bongs = bad RAM on that type of sound PCB. Checked the 74HC541 chips, 74HC245 chip, and the SRAMs. Found a dead trace between the GAL chip and the control circuit for the SRAM. Patched and tested.

[channelmaniac]

Model: Mortal Kombat II
Symptom: "Game glitches" and "has no sound"

Game had sound, but an incomplete cap kit done. Replaced the last 5 original caps and let the sender know they may have a wiring or power problem in their cabinet.

Reflowed the custom DMA controller IC on the game PCB and replaced a mis-matched program ROM with the correct one. One of the program ROMs was for version 4.2 Hacked and the other for version 3.1. Replaced the 3.1 version for the proper matching 4.2 Hacked version ROM. Tested.

[channelmaniac]

Model: Space Invaders
Symptom: Dead. White screen.

Board had attempted repairs done to it.

Replaced bad 74LS157 at F4 that had a weak output on pin 9. Found address line A0 had malformed signals. Replaced the 74LS08 at H3 to fix that. No signals were being seen on the Data In pins on all RAMs. Pulled the 74LS04 and socket at E4 the previous tech installed. Repaired a dead trace from the CPU to pin 1. Replaced dead CPU. Now had proper stripes on screen with ROM H8 pulled and CPU data lines were working.

Installed test ROM and found shifter problems. Installed game ROM and saw lines in sprites on the screen and Coin Up did not work. On the daughter board, replaced 26LS10 with stuck outputs and 74LS153 at B3 and D3 which had chattering outputs. Still had lines on the screen. Replaced the 74LS153 chips at B3 and D3 on the motherboard that had chattering inputs. Now sprites looked proper and the Coin Up worked.

Tested - no sounds. Replaced amp and pre-amp chips. Replaced a bad 120K resistor on the pre-amp chip that read 189K. No sounds. This one took a while to track down - both 74LS17 chips driving the sounds had stuck outputs. Replaced those and had all but 2 sounds. Replaced LM3900 chips at K4, M4, and K3/4 to restore the missing sounds. Tested.

[channelmaniac]

Model: Galaga
Symptom: Won't boot. When it does, it has corrupt graphics.

Board had been "rebuilt" by another company.

Board booted fine on the bench. Tapping on the CPU board would result in loss of clock stability where the picture would go crazy on the monitor. Replaced the socket on the 74LS107 clock divider flip-flop. No change. Replaced the defective 74LS107 as it had some kind of internal bond wire failure. Board was still unstable and would reboot or crash if handled roughly on the bench - a good test of Galaga stability after a rebuild. Looked board over and found 3 resistor packs that were not fully soldered into place. One had 1 of 5 pins soldered, another had 1 of 9 pins soldered, and the last had 8 of 9 pins soldered. Soldered the resistor packs, checked for solder shorts, then handled the board roughly with no reboots.

[channelmaniac]

Model: Space Invaders
Symptom: Dead. Garbage on screen.

Test ROM randomly booted and reported random RAM errors. Replaced bad socket and 74LS04 on the RAM outputs. Test ROM showed random bad RAMs. Burned a newer version of the test ROM (1.3 vs. 1.0) and saw that every other column of text was missing. Traced it back to a stuck pin 9 on the 74LS00 at B6. Replaced the 74LS00 and tested.

[channelmaniac]

Model: Ms Pac Man
Symptom: motion sprite color and position corruption

VRAM Addresser was floating around loose in the box.

Replaced damaged socket on the VRAM Addresser and tested. Replaced bad 74LS283 at 2F, bad Fast RAM at 2B, and bad Fast RAM at 2C. Tested.

[channelmaniac]

Model: Galaga
Symptom: White screen. Will not boot.

Board had attempted repairs done to it - cust installed a rebuild kit.

Found and fixed 3 solder shorts between solder pads for sockets and uncoated traces running next to them. Checked all resistor packs to find they were installed correctly. No boot. Checked clock/reset then found a dead trace between the Program ROMs and CPU 1. Patched the trace but still no boot. The 08xx bus arbiter would not pass data to the video PCB. Found 2H signal missing. The 07xx chip had been soldered into a set of stacked machine pin sockets and the pin for 2H wasn't making contact properly. Resoldered the pin and now it booted, but would reboot when trying to start CPU 2 and 3.

CPU 2 had pin 28 stuck low which affected memory address decoding. Found a solder short to ground under the 07xx chip. Board still rebooted. Found a dead trace between CPU 2 and its ROM. Patched and the board still rebooted when starting CPU 2 and 3. Board started losing horizontal sync causing the monitor to squeal. Replaced the 74107 chip in clock divider circuit. Board still rebooting.

Checked the 06xx chip and found the 64H signal missing. The hacked 07xx stack had been soldered to the cracked edge of the pin where it broke at the shoulder. Cleaned the top surface of the pin and made a proper connection. Board booted now but no explosion sound and no other sound. Explosion issue was that the 54xx chip was dead. Sound PROM at 5C read good on programmer but would not work at speed in the game. Replaced PROM and had good signals into the 74LS158, but not good outputs. Replaced it. Same bad outputs down the line with the 7489 bipolar RAM, then the 74LS283, and finally the 74LS174. Once the 74LS174 was replaced the sound came to life.