Tempest Troubleshooting help please

I have two Tempests, one working and one nonworking. Symptoms of the
nonworking pcb: When powered up, the "Press Start" screen is backwards
and upside down. It never shows the "Tempest" logo attract screen. The
start buttons blink, but won't start the game. When put into test mode,
the test box is displayed correctly right side up. I can cycle through
the test screens and they all are displayed correctly. When I flip it
back to game mode, I get one horizontal green line. Power off and back
on and I get the upside down backwards screen again.
What I have done so far: I have installed new rom sockets. I have
swapped the roms from the working Tempest into this nonworking board. I
have swapped mathboxes. The symptoms follow this pcb if I install it in
my working Tempest, and if I put the working pcb into this nonworking
cabinet it works perfectly. Fuses have been removed and checked. All
other socketed chips have been removed, cleaned, and reinstalled.
Voltages are ok. Interconnect ribbon pins have been resoldered.
Does anyone have any ideas what to try next?
Thank you.
jim

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Received on Mon Sep 4 09:51:20 2006