I am not sure if a schematic of the analog board is available on the Classic/Classic II. 

So I cant advise, Other than if you have another Classic/Classic II handy you can compare voltages against a known good one. 

But the classics are known for bad caps though. You may need to change all the analog board caps in both the power supply section, AND sweep section! then grab a DMM, set it in diode check mode and start checking for shorted diodes.