Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: pbman1953 on February 12, 2026, 09:37:14 am

Title: Fender Output balance pot resistor, out of spec, do I need to re-bias?
Post by: pbman1953 on February 12, 2026, 09:37:14 am

I had to replace a bad pot in  my Super Twin so I decided to check all the carbon comp resistors.  All were fine except the Output Balance , 33k 1w resistor , that goes to one side of the tube set. It's measuring 42k which is way out. All the others nearby 33's are right on spec wise.


After i replace that would you suggest a re-bias?


Thanks

Title: Re: Fender Output balance pot resistor, out of spec, do I need to re-bias?
Post by: stratomaster on February 12, 2026, 02:03:34 pm

Rebias or at least checking bias after touching anything in the bias circuit is a good practice.

If the components have drifted due to age/material composition, then I'd suggest replacing all resistors in the bias supply with much more stable modern resistors just to do the job once and for all. Address any aged electrolytic caps in the bias supply at this time.  Finish with a bias check and rebias as necessary.

Title: Re: Fender Output balance pot resistor, out of spec, do I need to re-bias?
Post by: pbman1953 on February 12, 2026, 04:17:43 pm

The 3 other 33ks are spot on spec wise. I replaced the bad one and it's balancing nicely

Title: Re: Fender Output balance pot resistor, out of spec, do I need to re-bias?
Post by: pbman1953 on February 13, 2026, 10:12:13 am

Another value to ask about-


 from Power transformer orange wire-


after the 035604 diode is the 47 ohm 1 watt resistor. It's measuring 54 ohms.


Since beyond the 10% should t be changed?   

Title: Re: Fender Output balance pot resistor, out of spec, do I need to re-bias?
Post by: pbman1953 on February 13, 2026, 03:16:18 pm

I replaced it anyway