Tempest

I have a Tempest game that (surprise) has been difficult to keep running.  When it fails, I'll pull the boards out, remove all the socketed proms, clean them and the sockets and reseat them and, it'll be good for another month or so.  Last time, I was seeking a more permanent solution so I reflowed all the solder connections on the prom sockets and the interboard connectors.  It worked for a couple of months but now, it has failed again.  I know it's the proms again because the self test works fine.  It's just when I switch to game mode that the screen goes blank. Two questions: 1.) I don't have a memory map so could someone suggest to me which proms contain the game software?  I don't want to bother those proms that are still working by reseating them again. 2.) Would replacing all the proms help?  I mean, besides the external connections do proms actually fail where they become flaky?  I've always thought that proms either work or they don't--not that they can only work sometimes. Thanks.
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Received on Wed Jul 11 16:19:46 2012