Centipede Woes

dirving

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Livermore Falls, Maine
Hi guys,

So this Centipede upright has been working for me since my last repair a year or so ago. I went to turn it on the other day and it appears to have lost sync and I can't for the life of me figure out why. Here's what I've done so far to troubleshoot:

1. Checked all connections, cleaned edge connectors, etc

2. Swapped out monitors with a known working one. Same issue

3. It was wired for positive sync, changed it to use the composite negative sync. No change

4. Played with H. HOLD, V. HOLD, etc on both monitors, changes have no effect

5. Replaced both 7407 chips (for both sync styles) at A9 and A/B10, no effect.

6. Cried and cursed most gods. No effect.

(Also, worth mentioning that game plays blind)

Any insight as to where to look next would be much appreciated.

Thanks,
Dave
 

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It's likely a bad chip somewhere in the sync/timing chain, somewhere behind the 7407's. It could be anything between them and the master clock. You'll need a logic probe to debug further.
 
It's likely a bad chip somewhere in the sync/timing chain, somewhere behind the 7407's. It could be anything between them and the master clock. You'll need a logic probe to debug further.

Yeah, I figured that's where I was headed, just was hoping that I had overlooked something stupid. I'll take stupid over logic probing anyday. Thanks!
 
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