Solid colors on screen, garbage noises


Voltages on the PCB (except for -30V, which is used for score save) seemed pretty close.  PCB and AR/II both worked in another Centipede setup, so the problem wasn’t with the boards. Must be a problem with power – replaced the Big Blue cap on the power supply, and things worked – albeit sometimes some wiggling of the connector was required.

Resolution: Replace Big Blue

Resistor blew on AR/II


Resistors R29 and R30, which are related to the 5V Sense line. Traced problem to poor connections between edge connector and PCB. Cleaned PCB side with eraser and rubbing alcohol, and tightened connector pins on harness side using a sewing pin. Connection was much tighter. Also replaced blown resistors. Adjusted 5V voltage while measuring on the PCB to get a nice, steady 5.00V. Game starts up every time now!

Resolution: Clean edge connector and replace resistors.

High scores don’t save


The top 3 high scores don’t save, and self-test mode always showed a message of “4 FF” (which indicates that the high scores are non-existent). Measured -13.7V on the -30V test point, which is related to the saving of the high scores. Replaced the 555 timer at A11 and C86 (1 μF 50 V) right next to it. Much better voltage (-26.4V on the -30V), but still getting 4 FF message and scores aren’t saving.

Need to try: actually getting a high score. If this doesn’t work, things to try:

  • Replacing the EAROM ER2055 ($4 from Bob Roberts)
  • Getting jrok’s EAROM replacement ($15 from jrok, theoretically more future-proof)


Leave a comment

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.