Centipede Repair Logs
Symptom: Garbage on screen. Enemies move erratically
Replaced bad RAM at M5. Logic probe showed erratic signals on DO2 (Data Output 2)
Symptom: Garbage on screen, reboots at random
Fired up test mode and received 9 beeps. Replaced the bad RAM at N7 and tested. Garbage was gone with the exception of horizontal lines on the screen. Cleaned the character ROM legs to fix the lines. Cleaned the program ROM legs to fix the rebooting issue then tested board.
Replaced a missing clock crystal and tested. Board came up with a white screen and CPU stuck trying to boot. Cleaned the legs on the program ROMs then the board would try to come up and had some random characters on the screen. Found where something scraped across the board, dragging some solder with it and shorting 2 traces. Removed short and tested the game. Replaced 2 broken transistors and retested.
Symptom: Board hacked
The MC14584 chips buffering the trackball inputs had been modified. Removed the 2 chips, 6 tacked on resistors, and 6 tacked on capacitors that were sticking out above the board. Removed 4 3.9k ohm resistors that were changed on the board. Installed 4 10k ohm resistors and 2 new MC14584 chips. Tested.