Brian E. Brzezicki
Copyright 2017
Version 1.00 03/04/2017

Note: Pacman and Ms. Pacman are basically the same hardware, in fact Ms. Pacman runs directly on a Pacman board with the original Pacman ROMs, just different video ROMs and a small daughterboard with extra code ROMs.

Disclaimer
Use these notes at your OWN risk.

Information

Game Board #1 03/03/2017

Problem:

  • board does not work, board #3 of a lot of boards

Troubleshooting/dianosis steps:

  1. can test 0x4c00 without VRAM addresser in
  2. same with 0x4000 - 0x47FF
  3. fluke bus test ok
  4. RAM long 0x4c00 - 0x4FFF - ok
  5. RAM long 0x4000 - 0x47FF - ok
  6. ROM 6e - 0x0000 - 0x0FFFF 8B1A - ok
  7. ROM 6f - 0x1000 - 0x1FFFF 8859 - ok
  8. ROM 6H - 0x2000 - 0x2FFFF 1934 - FAIL - 3370
  9. ROM 6J - 0x3000 - 0x3FFF 0A4B - FAIL 0 5E1B
  10. swapped 6e into 6J retest - FAIL - something is effecting when 6h or 6j is read
  11. address decoding issue? ROMs are getting read signal
  12. 7n ok
  13. 7l pin 9 and 10 ok
  14. 7m tested ok
  15. pulled 6J and trying to read - getting F3
  16. pulled 6h getting f7/f3 changing
  17. 6h and 6j pin 13 is not continuous with the rest of the ROMS can see where it's cut under 6h, - jumpered it
  18. ROM 6h tests ok now
  19. ROM 6j tests Ok now
  20. game works! no motion sprites have lines through them
  21. I believe problems with 2a and 2b which aare super hot and missing cermamic
  22. found more cut under video ROM sockets will pull, found 3 damanged traces under 5f with 1 cut
  23. lines gone but sprites wrong colors and and missing eyes
  24. non-sprites colors OK, probably these melted chips
  25. relacing RAM chips at 2a and 2b, sockets included
  26. that fixed the color and placement issues. - game works!
  27. tested in game 3/4/2017
Game Board #2 03/03/2017

Problem:

  • board does not work, board #5 of lot of boards

Troubleshooting/dianosis steps:

    board 5 - fluke bus test ok
  1. 0x4c00 - 0x4fff - BTS 0x0F
  2. 0x4000 - 0x47FF - BTS 0x0F
  3. swapped 4k and 4n, no change
  4. replaced 74ls245 @ 4h, no change
  5. 4k and 4n getting write signal and /cs signal on looping write of 0x4000
  6. put in 6e ROM check was OK, it's on a separate bus
  7. try cutting 8F, no change
  8. looping read 0x4000 - reading high on low 4 bits
  9. signals getting into RAM, however low RAMS are getting write enable spuriously
  10. took out other rams, problem went away
  11. ram long 0x4000 - 0x43FF - ok, moved them to 4400 - 47ff and 4c00 - 4cff - ok
  12. testing individual RAMS now
  13. putting rams in and testing. Pulling rams off other boards
  14. found 2 bad 2114 RAMS
  15. all 2114s are OK now
  16. when roms put in game works, but lines though screen, bad video sockets, push down and ok, will replace
  17. not for some reason images are all gone but plays blind, whoops forgot to solder in one pin
  18. z80 missing, all but 3 ROMS missing, needs new capacitors
  19. added new capacitors for power
  20. game works!
  21. tested in game 3/4/2017
Game Board #3 03/04/2017

Problem:

  • board does not work, board #10 of a lot of boards
  • Lot of previous repairs on this one

Troubleshooting/diagnosis steps:

  1. bus test - data bit 7 ties low
  2. pulled 6D to isolate rest of bus
  3. removed all 4 game ROM sockets , bus issue went away.
  4. it's back
  5. need to replace CPU socket, - replaced still getting bus issues on 7
  6. gone again
  7. RAM short 0x4000 - 0x43FF - DCD bit 0
  8. RAM short 0x4400 - 0x47FF - DCD bit 0
  9. verified that 0x4000 and 0x4001 are the same, but in different RAM still getting the same DCD error, will have to look at address buffers. Definitely getting 0 on address bus 0 regardless of 0x4000 or 0x4001
  10. need to look at 74ls367 @ 6S - replaced - no change
  11. address bit 0 is RAM bit A9 @ 15, it's floating, the trace that feeds it is damaged under a socketed, fixed
  12. ram short 0x4000 - 0x43ff - OK
  13. ram short 0x4400 - 0x47FF - BTS 0xf0 that is 4p - replacing with new one - ROM test OK
  14. ram short 0x4c00 - 0x4fff - OK
  15. Getting data bit 7 tied low again - went away and back again
  16. Removing bad repair of 74ls273 @ 4d will put in socket, replaced with new 74ls273
  17. testing ROM 6e 0 6j in circuit
  18. 6e - ok
  19. 6f - ok
  20. 6h - ok
  21. 6j - ok
  22. game working - sounds seem a bit off/high/canny
  23. replaced previously pulled 74ls273 no change, putting back original after socketing.
  24. Teseted resistors R6 - R9 - ok
  25. pulling 4066 @ 1N - no change
  26. replaced 4.7uf @ 10v cap @ c48 - no change
  27. replaced bipolar prom @ 1m with one from other board - sounds are fixed with that prom,
  28. original PROM was rusty, cleaned off, replaced socket, everything works fine now
  29. game works! - tested in games 3/4/2017
Game Board #4 03/04/2017

Problem:

  • board has static garbage on screen, board #6 of lot of boards

Troubleshooting/diagnosis steps:

  1. no sync on pin #6 of CPU (clock)
  2. getting 6 Mhz off of pin #13 @ 8B
  3. testing horizontal sync circuit
  4. 3r and 3s have fine outputs
  5. vertical sync looks fine except pin #15 on 2S maybe
  6. No continuity from #5 @ 8B to socket pin #6 on CPU (but OK to trace underneath)
  7. replacing CPU socket
  8. game now boots but sounds are high pitched and reboot, need to test ram
  9. reboot issue might have been lose VRAM addresser, still will test RAM
  10. Getting data bit 5 tied high on bus test
  11. There is a short between DB5 and /M1, found small solder glob bridging them under 6d, removed now bus test is OK
  12. RAM short @ 0x4C00 - 0x4FFF - ok
  13. RAM short @ 0x4000 - 0x43FF - ok
  14. RAM short @ 0x4400 - 0x47FF - ok
  15. game plays but with some bad sounds (coin up sound is super high pitched as well as startup song), will replace PROM socket @ 1m - no change
  16. Resistors R6 - R9 ok
  17. Noticed resistor r5 is broken off as is C1
  18. Replaced with parts from donor board
  19. Tried alternate PROM at M1, no change
  20. Tried alternate 3M prom, no change
  21. pulled 4066 @ 1N and socketed, no change, returning original chip
  22. K1 and L1 are ok
  23. bad bipolar RAM @ 2L, also replaced 2K as it broke
  24. game works!
Game Board #5 2/15/2018

Problem:

Troubleshooting/dianosis steps:

  1. Colors are directly generated by 82S123 @ 7F
  2. Replaced socket, no change
  3. Replaced 82S123 with a known good one from another board
  4. Blue is back, game works!
Game Board #6 2/16/2018

Problem:

Troubleshooting/dianosis steps:

  1. Checked voltage, it's OK
  2. /RESET is hight
  3. There is no clock
Game Board #7 2/19/2018

Problem:

  • Game is dead, missing many parts

Troubleshooting/dianosis steps:

  1. Replaced all missing parts
  2. Tested +5V - OK
  3. RAM long failed for all RAM ranges
  4. Check sync circuits
    • Horizontal circuits - 3r, 3s - OK
    • Horizontal circuits - 2r, 2s - OK
  5. Checking RAM address selection
    • All RAMs /WE are selected on write EXCEPT 4M (they all should be selected)
    • Removed 2114 @ 4M, noticed pin was bent and broken spanning multiple pins, replaced with new RAM
  6. RAM test 0x4000 - 0x43FF - ok
  7. RAM test 0x4400 - 0x43FF - ok
  8. RAM test 0x4C00 - 0x4FFF - ok
  9. Game works!
Game Board #8 2/21/2018

Problem:

  • Game starts playing but in intro ghost runs quickly across scren then game reboots
  • Constant Thumping sound coming from speaker

Troubleshooting/dianosis steps:

  1. Thumping sounds was a bad cap @ C31 (Thanks Mikesarcade.com, saw this on their repair logs! saved me alot of time!
  2. RAM long 0x4000 - 0x43FF - OK
  3. Ram long 0x4400 - 0x47FF - ok
  4. Ram long 0x4C00 - 0x4FFF - RAM patt err
  5. pulled 74LS367 @ 8d, no change
  6. Removed dirty socket @ 3R, that seemed to make resetting go away, though during play playfield started disappearing
  7. Put in new 74LS367 @ 8D, resetting started again, along with screen disappearing
  8. Game still not working
  9. I have had this issue with 4 or 5 boards and the only thing in common is I'm using a FPGA replacement for Sync bus addresses at 6D, replacing it with an origina 285 custom seems to fix the problem!
Game Board #9 2/24/2018

Problem:

  • Game does not work

Troubleshooting/dianosis steps:

  1. Voltage OK
  2. Fluke Bus test OK
  3. Fluke RAM long 0x4000 - 0x043FF - DCD error bit 7 @ 0x4000
  4. Fluke RAM long 0x4400 - 0x047FF - DCD error bit 7 @ 0x4400
  5. With both those same errors in the different RAM ranges it has to be somethign with the address decoding circuit
  6. Address line 7 is generated (After the CPU) from the 73LS367 @ 6R pin #13 output with input pin #14
  7. Did a writing loop at two addresses that would be the "same" if bit 7 is not working, 0x4000 and 0x4080 found that the input on pin #14 was correct in both cases but the output on pin #13 was always low.
  8. Replaced 74LS367 @ 6R
  9. Game works!