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54602A - Setup memories failed checksum test

Question asked by Philip on Sep 6, 2010
Latest reply on Sep 8, 2010 by Philip
I need a help to diagnose a problem with my old 54602A which displays the failure message...

illegal instruction: 0H

Setup memories failed checksum test - defaults loaded

I have located the service manual on this site and scanned through the table of contents, index and pages to determine how to move forward with this problem. I did not see a diagnostic flow chart, a description of a POST sequence nor a list of error codes/failure messages with probable regions of failure to investigate.

I wonder if such diagnostic aids exist and if someone would share them with me or perhaps impart their experience to help.

I assume the power supplies are sound as the VDU powers up and the processor/logic appears to work in so much that it results in displaying the message quoted. The 'defaults loaded' message perhaps indicates that settings saved the last time of use (Can't say when that was!) were lost although one could have expected the routine to continue then allow use. However, the system hangs - no soft keys are displayed - and - there are no responses to any key when pressed.

Inside - there are no smoke blackened bits - have removed much fluff (more like someone's beard), washed down the main board with solvent re-seated the PROM and looked over the components which all seem sound.

There's a couple of static RAMs on-board (6264) and a Non-Volatile SRAM (DALLAS DS1220).

I guess that the 'illegal instruction : 0H' relates to a firmware program vector that means the processor has not handled the exception properly! I suspect the NV-SRAM is responsible for the problem in some fashion.

Anyway, now I'm stuck ---> Please help or advise as what I might do next.