Author Topic: Midway Games (Read 103100 times)

channelmaniac · « **Reply #60 on:** May 07, 2014, 08:45:34 PM »

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 · « **Reply #61 on:** May 07, 2014, 08:45:44 PM »

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 · « **Reply #62 on:** May 07, 2014, 08:45:52 PM »

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 · « **Reply #63 on:** May 07, 2014, 08:46:05 PM »

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 · « **Reply #64 on:** May 07, 2014, 08:46:15 PM »

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 · « **Reply #65 on:** May 07, 2014, 08:46:44 PM »

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 · « **Reply #66 on:** May 07, 2014, 08:46:55 PM »

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 · « **Reply #67 on:** May 07, 2014, 08:47:04 PM »

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 · « **Reply #68 on:** May 07, 2014, 08:47:12 PM »

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 · « **Reply #69 on:** May 07, 2014, 08:47:22 PM »

Model: NFL Blitz 99
Symptom: Dead Short

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

channelmaniac · « **Reply #70 on:** May 07, 2014, 08:47:32 PM »

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 · « **Reply #71 on:** May 07, 2014, 08:47:41 PM »

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 · « **Reply #72 on:** May 07, 2014, 08:47:49 PM »

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 · « **Reply #73 on:** May 07, 2014, 08:47:57 PM »

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 · « **Reply #74 on:** May 07, 2014, 08:48:05 PM »

Model: Galaga
Symptom: Reboots, crashes

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

channelmaniac · « **Reply #75 on:** May 07, 2014, 08:48:23 PM »

Model: Galaxian
Symptom: Dead. Garbage on screen.

Reseated the ROMs. Address lines were stuck high. Data lines were dead. CPU stuck in watchdog reset. Replaced bad Z80 CPU and tested.

channelmaniac · « **Reply #76 on:** May 07, 2014, 08:48:32 PM »

Model: Ms Pac Man
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.

channelmaniac · « **Reply #77 on:** May 07, 2014, 08:48:42 PM »

Model: Mortal Kombat II
Symptom: Garbage on screen

Board failed video RAM tests. Reseated UB21, replaced bad battery holder, and tested.

channelmaniac · « **Reply #78 on:** May 07, 2014, 08:48:54 PM »

Model: Mortal Kombat II
Symptom: Game will not start

Board passes self tests and coins up. When P1 or P2 start button is pressed the game immediately shows "game over" on screen. Reflowed surface mount memory access controller chip at UE13 and tested board.

channelmaniac · « **Reply #79 on:** May 07, 2014, 08:49:04 PM »

Model: Ms Pac Man
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.

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Author Topic: Midway Games (Read 103100 times)