Tempest Board Passes Self Test, But No Game Play

From: Malcolm Mackenzie <maxstang_at_sbcglobal.net>
Date: Sat Jun 05 2010 - 18:40:00 EDT

Been working on this board for months on and off.  Looking for a bit of direction here. 

Board came to me completely dead.  Almost all of the RAM chips were dead and I ended up replacing the ROM set with a known working one.  CPU is new, and vector ROMs have been replaced with known working ones.  I've diode tested all the TTL chips on the board with no obvious failures.  Aux board  and cable are known working.  Headers reflowed

Current state of the board is it fully passes self test with stable video.  If I switch it to game play, I get flashes of text and sprites, but no tube and the scaling seems off as some of the sprites and text seem too big.  I also see selftest text flash on the screen during game mode. 

Anyone seen anything like this before?  Just need a place to start looking.  

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Received on Sat Jun 5 18:40:04 2010

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