Centipede archer goes up

KazooBR

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Donor 3 years: 2023-2025
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I've got a board with one remaining problem I can't solve. Everything works fine except the archer immediately moves upward on player 1 only. Player 2 is OK (I don't have my bench wired for upright so it flips screen orientation like a cocktail and chooses the second set of trackball inputs). It also moves up in test mode.

Passes ram/rom and bus tests with fluke 9010a.

I pulled the last chips in the trackball circuits … L9 and D9. The issue remains.

I have looked the board over many times, cleaned it multiple times assuming a short between traces. I would expect a short to affect both P1 and P2 though.

I've pulled the pokey and EAROM out. It happens with the original CPU and with the fluke acting as the CPU. Caps and resistors around the circuit seem OK too. I've spent a ridiculous number of hours but won't stop until it's fixed.

Any ideas?
 
Is your trackball opto jacked up?
Swap optos and see if it migrates to left right.

** those trackballs I got for you will ship tomorrow. Already in wife's car for ups drop off.
 
Not a trackball issue - I can plug numerous other boards in and it's fine. Definitely a board problem.

And pulling D9 and L9 takes the entirety of the trackball circuit out of the picture including the optos. These are the very last chips before the signals get dumped on the data bus.

Thanks for the extra trackballs. They will come in handy at times but I don't think for this one.
 
Not a trackball issue - I can plug numerous other boards in and it's fine. Definitely a board problem.

And pulling D9 and L9 takes the entirety of the trackball circuit out of the picture including the optos. These are the very last chips before the signals get dumped on the data bus.

Thanks for the extra trackballs. They will come in handy at times but I don't think for this one.
Don't forget - Centipede has circuitry for a joystick too. Could be in that area as well.

Brian

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