Re: 577 AC collector supply not reading zero on display

DW
 

What you describe makes sense Chuck. I observe no issues with smoke, hum, and the variac works throughout its full operating range other than not going to zero. Therefore I been convinced the variac as far as the winding is fine.

Having ruled out the variac, Bob made a good point about the carbon brush, I believe he is on to something about the contact point being worn down widening the contact area and potentially causing what I am experiencing. I will try to rework the brush to a point with some sand paper and see if I notice any improvements.

I would like to thank everyone here for their valuable help, I see this being useful for someone with collector supply issues to check the wiper brush!

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