Tech: Wells Gardner question (in Tempest)

I have a Wells 19K6100 monitor inside my Tempest machine that is exhibiting
odd behavior. I hope someone has seen this before and has a few directions I
can check that may resolve the issue.

The machine fires up and shows the game running - but in the lower half of
the screen. This is not like what I would expect for a deflection issue, as
the whole screen is fine, nothing missing - just all within the lower half
of the display. The game is fully playable like this. I initially thought
this was somehow related to the deflection circuit, so I began by checking
the Y amp circuit on the P314 deflection board. Other than a few wires
barely holding on (which I fully resoldered correctly) there were no issues.
All transistors and seemingly all voltages are fine. Every once in a while
the spotkiller will kick on briefly - then disengage and continue showing
the game.

I am starting to think that the deflection board is actually fine - and that
the game board may be sending lower than expected signals? I have found
nothing that helps to explain the expected input to the monitor.

Any ideas on where else I can double check this to narrow this down?

Thank you for any assistance.

-Ty Roden

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Received on Sun Aug 29 23:48:01 2010