Fault could be either the ADC chip or the signals controlling it. I
believe the 8340 permits direct control of the peripheral boards.
Diagnostic procedure would be to measure value at ADC input and look at
corresponding digital; values. You could pull eht ADC chip or try to run
the board in a home made test jig. Additionally, as I remember, there are
some board specific diagnostics that you can invoke.
Look over the board schematic and decide how best to attack the problem -
probably not the digital control signals as other boards using the same
control signals working (?).
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Hi there,
I am looking into buying a 8340A with known problem — Fault light on,
fault code ADC. From the service manual, it says ADC fault indicates CPU
detected ADC circuit problem on A27 level control assembly. When ADC is
faulting, SYTM won’t track and won’t peak.
However, the manual has very little information on A27 troubleshooting.
What would have caused the ADC fault? How does the power-on-self-test
determine the ADC circuit is bad? Could it be as simple as bad reference
voltage on the ADC or something very involved?
Thank you!
Calvin
