Plug your guitar into the 'power amp in' jack, is the hum still there?

Quote from: Tassieviking on February 22, 2024, 12:01:47 PMIt is usually a M205 fuse that costs cents, sometimes a ceramic type but still cheap.

My meter uses a regular fuse for the 2A range but has a special fuse for the 10A range (that has it's own probe port).
The special fuse is very expensive due to safety ratings and odd size.
You can find cheap ones from China but I think they are fake as far as the safety ratings go.
Mine is not a Fluke, but this will give you an idea:
https://www.fluke-direct.ca/online/fluke-instruments-replacement-fuses

If the hiss is so loud that the amp in unusable, it is likely a noisy transistor is the cause.
If you understand the signal path, you can try a cap to ground at various points along the path to try to isolate the location.  Something like 0.1 or 0.47uF rated 100V or more should work.
If the cap to ground kills the hiss, you know the source is somewhere ahead of that in the signal path, so you move the cap further toward the input and try again.

I think if you tweak it to get symmetrical you will still overdrive the stage anyway.  And it won't sound any better if it's clipping evenly on both sides rather than just one.  It's not really meant for that kind of guitar signal.
Some tubes amp do that as well, the gain stage before the volume control clips unless you turn down the guitar volume.  Just that with tubes no one really minds as much because the clipping is softer.

You can tweak the gain of the stage to deal with it, but you might just find the next stage or somewhere down the line clips the same way.

That's why I suggested getting full unclipped output and seeing what kind of input signal level that requires.

Have you verified that the input stage is the first thing that clips before the amp gets to full power?  Seems odd that they would have such little headroom at that stage.
At full power (just before clipping) into a load, what is the peak to peak voltage coming out of the first IC ?

Where did that example come from?  Why did they say the biasing resistors should equal R1?
The ratios are about RF and Rin and set the gain of the non-inverting op amp.  Your circuit and the example circuits have different gain so the "=1/2 R1" does not apply.

See this page:  https://sound-au.com/articles/gyrator-filters.htm

When you are getting the 1V from E-C, short the base to the emitter and see if the reading goes to open circuit.  If so, it should be ok.

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.