Bias adjustment pot. 112-RP-65, 2165RP, GP1

dinsdale

Greetings. I'm working on this 112-RP as a favor for a friend because it had a loud hum and was distorted. I did a complete recap. with quality parts found a few bad solder points and it seemed to be all good but while trying to set the bias per the MM service bulletin the adjuster pot seems to have become not effective after a few tweaks and tubes became very hot.
Is this common and are they available for replacement? This is my first stab at a PC board/transistor amp so I am being very careful with my de-soldering and soldering tasks. Thanks. Ed

Full Name
Lars Verholt
Music Man Equipment
HD-130 head, 210X cab, 210RH cab, RD-50 110 combo, Sixty-Five 112 combo, RP65-112

Member for

10 years 9 months

lmv Sun, 01/24/2021 - 15:23

Hi Ed

What sort of DC readings do you get? Do you know that the driver transistors and the grid voltage regulator diode are all good?

Sincerely,
Lars Verholt