A slightly sick AA501

[Zenwizard]

It seems I have some more sick gear on the bench. This time it is a AA501. It is reading a VERY VERY high distortion on clean sign waves. Like 100% distortion. This is when sine waves above 1Khz. As soon as the frequency drops below 969 Hz the function output collapses in to what appears to be a possible oscillation somewhere in the THD circuit. It does not seem to do this in the voltage detection mode only the THD mode. I am thinking I might run it through a Cal process and see if it is a pot that is WAY out of adjustment or if there is larger issues. Switches have been cleaned. Any input would be appreciated as to the next steps in the troubleshooting process.

Thanks for the help
Zen

[jonpaul]

Did you recap the radial tamtalum capacators,they are notorious for shorting or loading  power rails.

Just a thought,


Jon