Midway Games

[channelmaniac]

Model: Galaga
Symtpom: No sound and graphics problems

Installed a renew kit (new 24/28/40/42 pin sockets... resistor packs did not need replacing), cleaned all chip legs, and reinstalled the chips into their new sockets. Tested game. Game now works, with sound, but has a strange graphic anomaly: The player and enemy ships are all tilted to 45 degrees, player explosions are divided into four pieces, and enemy explosions are numbers 20 over 31. If the enemies are tilted to the left the numbers are upside down and if they are tilted to the right the numbers are right side up.

Checked the Graphics ROMs on the video board. Pins 1 and 2 were stuck low with very rapid racing pulses. Checked the 74LS153 at 1B and found it had normal inputs but bad outputs. Replaced the IC and tested the game.

[channelmaniac]

Model: Galaga
Symptom: Missing some blue on motion graphics and random blue streaks on board

This was a very tough one to track down. The board worked fine until an extended burn-in was done. Swapped out the motion RAM (8 x 2147), the resistor packs that hold the data lines high, 1 PAL, and a couple other 74xx chips. Replaced the 74LS298 at location 5B to fix the missing blue. This chip multiplexes the 8 data output lines from the motion RAM into 4 for mixing with the text graphics and later with the starfield.

The random blue streaks was just as tough to track down. Checked the 74LS365 chips at 5A and 6A, swapped out 2 of the replacement Video RAM chips, and checked the 74LS157 at 4A. (Yes, 4A. It says 5A on the schematic, but there's a 74LS365 at that board location. The schematic has an error.) Traced the problem back to pin 10 on the 74LS20 at location 3A which feeds the LS157. Pin 10 is the 6MHz* clock. Swapped the 07xx IC to no change. Replaced the 74LS368 IC at location 3N to finish the repair.

[channelmaniac]

Model: Ms Pac Man
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.

[channelmaniac]

Model: Pac Man
Symptom: Random reboots

Cleaned the Z80 Sync Bus controller chip's pins. This was the old custom chip version with tarnished legs, and not the daughterboard. Replaced the bad CPU socket and ROM 5E sockets to finish the repair.

[channelmaniac]

Model: Pac Man
Symptom: Dead hacked board.

Board was poorly hacked and had jumper wires that were not soldered on one end.

Removed the 8 EPROMs for the Ms Pac Man bootleg hack, removed several jumper wires, fixed 5 cut traces, and installed freshly programmed Pac Man ROMs in rows 5 and 6. Tested game.

[channelmaniac]

Model: Ms Pac Man
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.

[channelmaniac]

Model: Ms Pac Man
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.

[channelmaniac]

Model: Galaga
Symptoms: Graphics corruption

Replaced every tall, flat style resistor pack and tested. These packs are sources of a lot of problems on Galaga boards.

[channelmaniac]

Model: Galaga
Symptom: Dead. Garbage on screen.

Installed all new 24/28/40/42 pin sockets. Cleaned the custom chips. Board would run but would die when hot. Replaced CPU at 4M to finish the repair.

[channelmaniac]

Model: Ms. Pac Man
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.

[channelmaniac]

Model: Galaga
Symptom: No coin inputs and faint garbage lines on screen during self test

Replaced bad resistor pack at location RM10 to fix coin inputs. Replaced EPROM sockets and 42 pin socket on the CPU board. Replaced all 24/28 pin sockets on the video board. Tested. Replaced bad PROM at location 2N to fix the faint line issue and retested board.

[channelmaniac]

Model: Galaga
Symptom: RAM 0L error

Replaced all resistor packs and 24/28 pin sockets on the video board. Cleaned legs on the custom chips. Board then fired up with a 2L error and random garbage on screen. Garbage would change when pins 1-7 were checked on the SRAM with a logic probe. Replaced bad 04XX chip and tested. Replaced all 24/28/40/42 pin sockets and all of the resistor packs on the CPU board. Tested.

[channelmaniac]

Model: Pac Man
Symptom: Dead

Board was part of a group of 7 boards sent in for repair. It would not try to boot and was stuck in watch dog. Replaced CPU socket then board would try to boot but fail. Checked the ROMs and found Pac Man Plus ROMs on the board. Reprogrammed the 4 program ROMs and 2 character ROMs and tested. Board had Pac Man PROMs so the colors were OK.

[channelmaniac]

Model: Pac Man
Symptom: Dead

Board was part of a group of 7 boards sent in for repair. It would not try to boot and was stuck in watch dog. Checked the ROMs and found a rotted pin on 6E and a mixed set of bootleg ROMs for the remaining 3 on row 6. Replaced the bad ROM and reprogrammed the other 3 program ROMs and tested. Board had a Pac Man Plus PROMs at 7E which caused the board to output incorrect colors. Replaced the PROM and tested.

[channelmaniac]

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.

[channelmaniac]

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.

[channelmaniac]

Model: Ms Pac Man
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.

[channelmaniac]

Model: Ms. Pac Man
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.

[channelmaniac]

Model: Galaga
Symptom: White screen. Dead.

Board had been worked on before. Installed a renew kit (new 24/28/40/42 pin sockets & all resistor packs) on the CPU board and found that 2 of the 08xx chips on the CPU board had pins bent under them. Repaired the pins as they will snap off when straightened, cleaned all the custom chips and tested. Game now worked but had no starfield and had blue lines on the screen.

Installed the renew kit on the video board, replaced the starfield generator, cleaned the pins on the custom chips and tested. Replaced the 2147 at 6L to fix the blue line issue and re-tested board.

[channelmaniac]

Model: NFL Blitz 99
Symptom: Dead Short

Replaced 2 shorted tantalum capacitors on the -5v line and tested.

[channelmaniac]

Model: NFL Blitz 99
Symptom: Will not work in Standard Res mode

Tested the DIP switches and found that U8 Switch 2 was stuck open. Replaced the surface mount DIP switch with one from a parts board and tested.

[channelmaniac]

Model: NFL Blitz 99
Symptom: Buzzing sounds from speakers, won't enter test mode

Board was VERY dirty. Cleaned board and replaced both sets of DIP switches. Audio issue was very odd. The hard drive, video, and any other operation could be heard through the speakers. The noise could be seen as ripple on the +5, -5, and +12v lines and No audio from the game was present. Pulled the D/A converter with no change. Pulled the audio op-amp and noise disappeared. Replaced the op-amp and reinstalled the D/A converter then tested.

The bad op-amp was overdriving the audio output IC and causing the loud noise. The overdriving also caused large current pull from the power supply which showed as ripple on the outputs and as noise through the speakers.

[channelmaniac]

Model: Galaxian
Symptom: Distorted characters/text and text wrapping around right side of screen

All address and data lines were present but not proper on the character ROMs. Shorting A1/A2 together made the garbled blocks look more like text. Checked the 74LS273 at location 2M and found output pin 9 was dead and pin 6 was strobing. Replaced the IC and tested the game.

[channelmaniac]

Model: Pac Man
Symptom: high pitched beeps and blips instead of normal sounds

The beeps and blips occurred at the same time and cadence as the normal sounds. Replaced the 74LS273 and checked the PROMs by both checksum and substitution. Replaced the 2 bi-polar RAMs. No change. Compared signals to a working board and found all the enable lines were correct. Replaced the 74LS283 at 1K to fix.

[channelmaniac]

Model: Galaga
Symptom: Reboots, crashes

Installed renew kit and replaced 1 cracked 1K resistor. Tested.