The output level on my BK Precision 4017A function generator is drifting.
For example, if I set the output level to 10.0V on a 2kHz sine wave, driving a variety of simple half-wave rectifier and diode clamp circuits, the function generator output level will hold fairly steady for perhaps 10 or 15 minutes then drift down to around 6 volts or up to around 15 volts over a period of a couple of minutes, then settle at the new level for a while.
Any suggestions what might be wrong please e.g. dodgy potentiometer, capacitor, or transistor, or are there just too many possibilities to diagnose? I have read the manuals, Googled FG trouble shooting (a lot on frequencies but nothing so far on output level) and emailed BK Precision support but no reply and I guess they are closed now for the weekend.
Best Answer
In case this is useful to others with similar problems in future, I opened up the function generator (power off and unplugged) and gently poked a few things, especially the output level potentiometer. Since then, the output level was dead stable for 4 hours yesterday and again for two hours this morning, so it seems to have fixed it, for now at least.
Link to other suggestions people made in addition to those above, with schematic and photo with the cover off.
As a follow up two weeks on...
BK Precision recommended first checking the output level potentiometer (spot on, it has been stable ever since) and have since dug around in their files and provided a component list with zoomed in sections of the schematic. It is a pretty ancient machine (schematic is from 1994), so all in all I say brilliant customer service from BK Precision!