Solid State Guitar Amp Forum | DIY Guitar Amplifiers

Transformers produce AC voltages, and those voltages are called RMS voltages.  SInce AC voltage changes all the time, we use an average.

36v AC, moves from zero up to a peak of About 51v, then back down through zero and out to -51v and back.   The average of that zero to 51v is 36v.  When you rectify and filter that, the caps charge up to the peak of 51vDC.   This is how it works.  You take the RMS AC voltage of the transformer, and multiply by 1.414 to get the peak voltage, which will be the rectified and filtered result.We might subtract a volt or two for losses in the rectifiers or some such, but that basic formula is close enough.

He said it was the Studio Pro

What?   Just what large cap were you expecting?  This is not a single rail amp like older Acoustics.   Look at your schematic.  RUns on plus 42 to minus 42 volts.  Not plus 90 and ground.  The output sets at zero.  No need for a fat cap.  The fact it is quasi doesn't matter.

Your schematic shows no output jacks.   But if I were to guess, I'd say the extension jack puts the extra speaker in series with the main, rather than parallel.  SO the sleeve can be grounded, and the tip cutout goes to the sleeve of the main jack.   Thus the main jack needs to be isolated.

Why would they do that?  If they made it parallel jacks, then any moron could plug a couple 4 ohm cabs in there and load the poor amp to 2 ohms and blow it up.  Now a couple 4 ohm cabs makes an 8 ohm load.

We do find schematic errors now and then, but I think it is wise to resist the urge to immediately label something we don't understand as a mistake.

I am not where I can post at the moment, but google "Peavey semiconductor cross reference"  or "peavey semiconductor guide".   Many places will have it for download.

And did we unplug the footswitch?

Is the FS the real Fender FS for this model?  Or is it some stomp switch you had from something else?

Is there ANY sound in the speaker?  BAckground hum maybe?

Turn up the reverb and bang on the amp to crash the springs.  Does that noise come out?

The Hot Rod series do have some things that happen to a lot of them, BUT, there is a difference between "When they fail, THis is what often happens" and "This usually fails in an amp."

WHEN an amp comes in with channel switching problems, I know to look at the two hot power resistors.  But that does NOT mean that all the aamps do that.  Most of them do not have a problem.

"Leaky" caps don't usually look different.  The leak refers to electrical operation, not some goo oozing out.  That can happen too, but it rare.

My point being I generally do not like pre-emptive wholesale parts replacement.  We would be more likely to cause problems than to prevent them.

U3 and all those caps are the chorus clock circuit, they are not in the audio path.

U2, U7 Q6, Q7 are the chorus path.  MAybe Q5 too but I doubt it.  Turn chorus on, you get hiss.  Power off, remove U2, power on.  His still there?  You won't get a chorus signal with U2 gone but we are looking for the noise now.  Still noise?  Remove U7, same question?

Make SURE not to install ICs backwards.

It is fun to try to tweak an amp for tone, but remember, no matter what you do to a hamburger, you will never make it taste like a lobster.