Yes, it is possible for electrolytics to self-heal.  Whether it is temporary or permanent is another question.   

Agree with Phatt, tank should be ok.  Fix the reverb first, then change tanks if you still want to.
Sometimes there is signal but not enough.  The tank takes quite a bi to drive it.  You said you thought it was appropriate but what is the level you are getting in to it?
Also you should be able to get very loud crashing from shaking the tank if reverb and volume are both turned up.

If it is running the chips with single supply, it will have blocking caps at input and output of IC.  Check that they are not leaky.
Also check for protection diodes at IC input.

Normally I would say yes, it is in the power amp section.  But you also said the tone controls affected the sound of the ticking.  If the tick was just in the power amp the tone controls should not affect it.

The item that is common to both the preamp and power amp is the power supply.  But it would still be good to run the preamp out (FX send) to a different amplifier and verify if the tick is there or not.

Your math is off by some factor of 10 I would think.
He has 6.3V and a 47K resistor, you have roughly 3 times the voltage, maybe should have 120K instead of 1.2M ?
Re-check your calculations.

Excellent.  Have never seen one with a stand like that, usually they clamp on to desk.
I like this so much more.  I think I'll try to cobble something together with my desk mount lamp and a broken mic stand. 

Quote from: mccutter on January 13, 2024, 09:11:44 AMIt's called CR13 (one of these in the heat sink)
Seems to be good but the vf value is different from the others (616mv vs 840mv)

CR10 to 13 are critical to the bias circuit as they compensate for the heatsink temperature.  The Fender part # for them comes up as BYV26E.  You should replace all 4 just to be safe.

Also, what I said earlier about checking for DC with no load won't work on this amp, because of the IC driver.  You will need some resistor on the output instead of the speaker, 1K should be safe for testing.

Do you have any electronics on your person?  I don't know many people who do not.  Turn them off and see if it has affected anything related to the fault(s).  It may seem like a long shot but it's something that must be eliminated as a possible cause.

What is that BYV26D diode called in the circuit?  CR18 or 19?
Disconnect one end of it and recheck.

Once you learn all those equations backwards and forward, you will have a much easier time with practical applications like multiple speaker cabs with speakers of various impedances.  Then you can throw power handling into the mix and find the weakest link.   

I don't think they will provide any service documentation for anything they make, even to dealers.
For that, and the SMT issue, you pretty much have to send to them or their authorized station.
But I would check with them whether you could send the board rather than the chassis.  That would save a lot of weight for shipping.

You said you heard a buzz before when powering up, so I assume you had the speaker connected.
It is best to first power-up with no speaker or load connected.
Then check that transistors are not overheating and there is no DC voltage at the output.
If all that checks out, then connect speaker and test.

Yes, I see now.
From the voltage drop (across the 2K2) you had with the 741's, assuming you are again at 22V with the 820R, you have increased from 8mA to 22mA.

So there is no defect, just an imperfect part substitution.  TL071 would have been a direct drop-in replacement with no mods.

The amp was working before with the 2K2 resistor, so changing it is just a 'band-aid' solution to some fault in the low voltage powered circuits.
You need to repair it rather than modify.
37V across 2K2 was 16mA of current, where was it going?

Does your friend have a multi-meter and know how to safely work inside of amps with power on?
If so, I would start by verifying that the preamp is getting it's proper DC voltages from the power supply.
This can be done by measuring the DC volts at both sides of the following resistors:
R20,R45,R29,R72,R10,R5