Amp bias fluctuates 6 to 7 mV

[VintageNut]

I have one of my SX-1050 that the bias fluctuates by about 6 to 7 mV
Could this be caused by the trim pots being dirty? I see no way to clean them. I know EW mentioned replacing them with Bourns pots in some posts. Or, is there another compnent on the amp board that could be causing this?

 

[Lefty]

Most likely the pots, they are pretty course control even when new and after many years with the pot contact touching the same carbon track spot, well they just are not as precise as one would like....

Lefty

 

[VintageNut]

it's supposed to be 50 mV per the service manual, I just looked at it again, with a meter on it, it fluctuates from 45 to 54, so it's 9 mV. Is there a way to clean the pots?

 

[VintageNut]

I don't really see anywhere to put the deoxit in

 

[VintageNut]

Hang on, I shot some from the backside in. I'll work the rotary switch a few times, and try again. In case anyone wonders about a SX-1050, the service manual is correct. Counterclockwise is zero mV for the bias

 

[Pioneer727]

I have had only one receiver that I could set the bias right on most had a value from 4 to 6mv from spec. I am going to replace them in my 1050 and see if it makes a diffrence.

Ron

 

[VintageNut]

Yeah, I'd like to know if the Bourn pots would do the trick. 2 of my SX-1250 receivers would hold nice and steady at the designated bias mV