Centipede Screen Issue

Zud

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The cocktail cab has issues. It has random letters on the screen. What should I try? Reseat roms or just burn new ones?

Here is a link to the pictures of my purchase: Bulk Buy
 

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FYI: When I try test mode the screen goes blank except for a line of characters running vertical. Starts with the letter P followed by H's all the way down the screen. There is also a constanting beeping. None of the buttons work while like this. If I switch the game back to game mode it works fine other then the random charcters you see in the previous pictures.
 
Could be one or more bad screen RAMs. Check the manual for a description of the beeps.
 
It could be watchdogging before it has a chance to report. Check the usual suspects - voltages, reseat the Pokey, CPU, program ROMs. In fact, if you have a CPU and/or Pokey from a known-good board, try swapping those in. Also check for obvious physical damage to the board, ie. shorted pins, broken traces, etc.
 
If it is watchdogging in test mode, you could try jumpering the watchdog disable lug to ground. Once in awhile you get lucky, and it will then let test mode run and maybe give an error.

Edward
 
Clean the legs on the ROMs - inside and outside surface - and put them back in the sockets. I've had a couple of Centipede boards here that were making poor contact because the metal to metal connection between the legs and the sockets were oxidized. You could see a little dark spot on the legs where the sockets were making contact with them.

Once you do that try to go into test mode again and see how many beeps you get to find the bad RAM. You have at least 1 bad RAM chip.

RJ
 
Screw it, I just swapped boards and good to go. At least now I have a working board to compare off of.
 
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