Disclaimer
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 ;)

Centipede Troubleshooting Information

Game Board #1

Problem: Game is dead No picture Tying to start in test mode provides no beeps Troubleshooting/dianosis steps: Using a logic probe, I noticed that the CPU wasn't doing anything, no address lines flipping, data lines are not flipping. Checked the clock line on 6502 with a logic probe... no transistions Replaced slightly dented original 8.2 Mhz crystal with a new 8.0 Mhz crystal - game now boots up but missing tiles, some tiles flipped upside down, ghosting on the screen, distored images Put game into test mode, 10 beeps Replaced 2101 SDRAM at N5 (according to the Centipede diagnostics page Game passes test mode.. missing tiles returned.. still some tile ghosting (spiders) and mushrooms have what looks like a period (.) in the bottom right corner, but looks promising, especially since it passed test mode and all the graphic tiles are back and game demo is running,problem gets less if you turn up the voltage higher but never completely goes away ground pin (pin 12) on F7 was not actually making contact with the ground line. (I damaged the trace when I replaced the ROM socket). solder a wire from pin 12 to ground, and that fixed the video problem

Game Board #2 1/14/2012

Problem: Game is dead No picture Tying to start in test mode provides no beeps Board missing crystal, broken cap, missing ROM Troubleshooting/dianosis steps: Replaced crystal Replaced broken cap (not needed just a TTL chip power filter cap) Replaced missing ROM Still didn't do anything on power up Using a logic probe, I noticed that the CPU wasn't doing anything, no address lines flipping, data lines are not flipping. Checked the clock signal with a logic probe... no transistions Used schematics to trace clock signal backward, found 74LS163 dead at position P2, replaced Game works

Game Board #3 3/31/2012
Problem: video unstable at normal voltage (+5V) Ground pad on edge connector looked like it was repaired before Some other pads had had been flowed with solder, making them significantly thicker Troubleshooting/dianosis steps: re-repair ground pad, used 18G wire to run bottom pad to top pad and expand connectivity on top pad unsoldered extra solder on other pads, flattened the pads out Game works

Game Board #4 4/4/2012

Problem: Power pads on edge completely blacked or missing Ground pad on edge connector was chared, pad next to it was disentigrating Board had excessive amounts of solder re-flowed onto the pads, creating an uneven surface Troubleshooting/dianosis steps: repair ground pad with copper foil tape, used 18G wire to run bottom pad to top pad and expand connectivity on top pad repair pad next to ground with copper foil tape removed excess solder on other pads Game works

Game Board #5 4/4/2012

Problem: One of the cleanest centipede boards I've ever seen... but... Game won't power on at all. Power supply shuts down immediately when plugged in Switching power supply will immediately shutdown after turning on Voltage regulator VR2 missing Cap C99 missing Troubleshooting/dianosis steps: Measured no resistance between ground and +5V. There is a short... but where is it? Hooked up computer power supply hard drive connector +5V and ground. Wired to +5V and ground on the centipede PCB test points Powered on computer supply. Immediately smoked 47LS153 at E8 Remove E8, replaced with a 16 pin socket and a new 74LS153 That fixed the short Replaced 7815 Voltage regulator at VR2 Game works!

Game Board #6 5/4/2012

Problem: cpu is half out of socket and pins bent, board very dirty, 7815 at VR2 has been badly replaced. Troubleshooting/dianosis steps: resocket CPU replace 7815 voltage regulator at VR2 do memory test, replace chip M5, memory issue still occurs use fluke 9010a, memory shows the most significant bit is bad. Trace lines to find that there is a piece of metal shorting MSB output with another line, remove and everythign works.

Game Board #7 5/4/2012

Problem: Game missing graphics ROM F7, missing voltage regulator at VR2, 12Mhz crystal is broken off, edge connector has had solder applied all over, 4 position DIP near NI1 is broken. Troubleshooting/dianosis steps: Pulled out other ROMS, all of them had missing pins Replaced ROMS Replaced 12Mhz crystal Replaced 7815 voltage regulator at VR2 Removed solder on edge connector pads Noted that it looks like IP at F6 was previously replaced booted board up, self test gives 3 beeps (K7), confirmed with Fluke, address 0x0400-0x040F (K7) show errors in high 4 bits (0111) which corresponds to 2101 at K7), replaced K7 Capacitor at c78 was looking rough, replaced board works Still need to replace 4 position dip switch

Game Board #8 5/4/2012

Problem: 12Mhz crystal is missing, all code ROMS missing (D1-J1), CPU missing, POKEY missing, EAROM chip missing, 8 pin dip switch @M9 broken Troubleshooting/dianosis steps: Replaced CPU Replaced POKEY Replaced ROMS Replaced 12Mhz crystal Powered on, LM324 at K10 smoked then power supply turned off... short circiut Removed LM324 board powered up, no sound, replaced LM324, sound is good run self test gives 8 beeps (M5), confirmed with Fluke, address 0x0420 (K7) show errors in high 4 bits which corresponds to 2101 at K5), replaced K5 board works Still need to replace 8 position dip switch