Amp repair where do I start

[LoveChet]

I wish I had a capacitor value checker but I don't!

[Helmholtz]

If you have a 470p or 1000p cap with sufficient voltage rating you could try that in place of the 250p.

[LoveChet]

Continuity is good for all six wipers.
However when the fat switch is in position 1 there is a direct short from the treble pot to the 250 pf cap (by design) therefore if I'm going to short out the 250pf as a test I don't want it in position 1 since dc would get into treble pot. SO, I will put it in position 6 if I plan to short out the 250pf test

[Greg Robinson]

Yes, correct, you must have missed my edit above, sorry.

[LoveChet]

Makes no sense. Checking right at upstream side of the 250pf cap I get that low ungained signal. However when I check right at pin 1 of the data switch it shows 4v. It's a direct connection between the two !

[Greg Robinson]

Quite possible you didn't break through a layer of oxidation when you were probing earlier.

So have you measured signal level at the output of the treble pot wiper?

[LoveChet]

Shows 4v at pin1 of fat switch and it doesn't matter what of the six positions of the fat is in

[LoveChet]

Yes. I suspect I'm not getting good connection right at the cap !

[Dave H]

Yes, it's more like a "Thin" switch.
The "Fat" switch is usually a single cap in parallel with the 250p

[Helmholtz]

Does the treble control work with a guitar?

[LoveChet]

Yes they do. In fact my Fender Deluxe Reverb which is a popular model has only a treble and bass pot (no middle pot).

[Helmholtz]

So it seems the 250p cap is actually good.
Next I'd check output power on a dummy load.

[Helmholtz]

Yes, it's more like a "Thin" switch.
The "Fat" switch is usually a single cap in parallel with the 250p

That's why I suggested the increase the value of the 250p cap.
The series caps around the rotary switch will then allow to lower the effective capacitance to a useful value.

[LoveChet]

Problem solved. Cap test point had varnish on it. I'll get some output readings at treble wiper and then move on to v2 2nd stage

[Greg Robinson]

I suspected we were jumping into diagnosis without being sure there was actually a problem. Let us know test results.