Brian E. Brzezicki
Copyright 2013
Version 1.00 11/22/2013

Use this at your OWN risk, do NOT sue me if it breaks your board... if your doing this your board is probably already broken though ;)

Game Board #1 11/22/2013


    Game is dead, no image on screen, 1 and 2 player start are solid lit

Troubleshooting/dianosis steps:

  1. Tested RAM 0x0000 - 0x00FF and 0x0800 - 0x08FF on Fluke long RAM test - OK
  2. Tested ROMs against known good signatures - OK
  3. Probed !RESET pin on CPU, it's constant low
  4. Disabled watchdog, RESET goes high, but game does not work
  5. Used fluke to write to watchdog memory address, noted that when writing the reset pin changes to high but stays high even if I stop writting to it.
  6. Noted HSYNC does not transition
  7. looked at schematics, tested 74LS74 at P2, found pin 5 was low, pin 6 (opposite state of pin 5, transistions) replaced chip, new chip pin 5 is STILL stuck LOW
  8. Pulled out 74LS74 tested pin 5 and without chip and found it still low
  9. Looked at schematics traced pin to pin 2 of N2 and M2, removed those chips
  10. Found pin 5 is STILL stuck low
  11. manually traced pin 5 on lower side of board to 72LS02 @ N8, snipped pin and found that pin 5 of P2 was no longer stuck
  12. resocketd and replaced the 72LS02 @ N8 and the 74LS163s at N2 and M2
  13. RESET is no longer stuck low (is high now) and HSYNC is transistioning
  14. game boots up passes self test and seems to work, graphics seem to be black and white only, need to look into that whether normal or not