504 MPU System Error

[Ash100]

Hello,


Was testing some boards today and ran into a couple of them that would not fully boot.


The VFD would cycle between EEPROM Error and System Error.


It would then give me a message that read Bad Serial Number ROM -0xAE03


I would get this message over and over after EEPROM Error, Press Test Switch, Close Door, Initializing, Testing Memory, System Error. Turn key, Press Test Switch, Close Door and so on.


Anyone run into this before and may know if a way to repair it?


It's happened on 2 boards so far. If I leave it sitting long enough powered on, eventually it will say Displays Netplex Link is down.


I've swapped chips, I960 and checked for bent pins. No corrosion damage, Varta previously removed.


Hate to trash 2 more boards.


Thanks. Curtis ash100

[Stayouttadabunker]

...If I leave it sitting long enough powered on, ...

That's a BIG CLUE right there Ash.

Technically I don't know specifically which IC component on any circuit board is going out of specifications and causing errors,
 but it is DEFINITELY something overheating.

Believe or not, the problem can even be a badly crimped or oxidized pin in a connector housing. 

No one I know knows how to decipher...>>>  [-0xAE03]

We need an IGT god that might have a sheet on those VF display codes. 

Or, perhaps someone had this particular problem before and can chime in to help ya.