Fender 94 Twin Amp with strange broken pot

[Randall]

This is the black knob verision, came in with the shaft pulled out of the Ch 2 volume pot. The push/pull is channel switching. First off, I had a bear of a time getting about half of the knob set screws to turn. They were so tight, some of them released with a crack using the biggest screwdriver I could fit. Then, about half of the pot nuts were on so tight I could not release them with my Excelite nut driver, I had to use a 9/16" socket and wrench. WTF.

When I got the board out I saw the pot body and switch box pushed back away from the chassis enough that everything seperated and fell apart as soon as I unsoldered them from the board. Tabs were bent, and parts were distorted like it took and awful hit. Yet, this does not reconcile with being bolted to the chassis and a big skirted Fender knob that would not allow this kind of inward pressure.

So I am left wondering, how did this occur?

[nevetslab]

Man, you sure took in a puzzler there! Very few times have I been unable to back out the set screw on the 'standard Fender Skirted knobs as used on the 94 Twin Amp. I gather no signs of moisture or rust on the set screws. Rust & time will yield them to be a PITA, but nothing like what you found here.

I agree with your assessment....how the dickens could a front hit on a knob drive the shaft back thru the bushing to take out the pot, since the knob would bottom out against the chassis front panel. All those pots use an 11mm hex nut. 9/16" nut? yes...WTF? I've had to replace that push-pull volume pot more than once, but never encountered what you've found this time. I've certainly had set screws strip out, but locked into place? Only thing I can think of there was someone must have thought using loctite on the set screw was the thing to do.

[Leo_Gnardo]

Agree with nevets ^^^ (as usual) AND if there were 9/16 nuts on all the pots, not the usual half inch or 7/16, I have to think someone replaced them all with non standard hardware, and may have gotten happy with the Loc-tite or krazy glue Perhaps the pot damage happened before the pot nuts & knobs were skunked up, and the last "tech" inside decided to retreat without fixing the pot. Hope you can get this amp sorted without any further problems!

[Randall]

My bad, it was 7/16" not 9/16".

[nevetslab]

I think it was back in the days of being a bicycle mechanic, where I discovered 11mm & 7/16" wrenches and sockets worked on the same nut. Same with 14mm & 9/16". And a 13mm 12-pt socket will drive the 1/2" square bolt in Greenlee Chassis punches. Nice to have the leverage and ratching handle driving chassis punches.

Not that any of this has to do with Randall's puzzle on how the heck did this Twin Amp get so afflicted with abuse.

[Justin Thomas]

Also 16mm & 5/8", I believe... & 19mm & 3/4". But that doesn't really apply to amps. That's just on Fords.

Jusrin