What neutral, what 22K?  You are scaring me a bit now so maybe stop til you can draw out what you are doing. 

Man....  
I have to say I'm totally floored 

Started hooking it up

I can't believe what I'm seeing

PACO's not even turned on yet and the AC is traveling through its neutral and the 22k resistor

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Now I'm scared to turn PACO on   

Put the DC supply in series, between the bottom end of TX secondary and ground.
Your drawing shows it in parallel, across the TX secondary.

Quote from: g1 on August 07, 2026, 11:33:05 AMTrim pot AP1 is the adjuster.

I haven't touched it because it told me that it was the pot "that calibrates the reference level from the preamp and the power amp", and it was "calibrated from factory" so I listened and Kept my hands away from it

Quote from: Kaz Kylheku on August 08, 2026, 11:04:46 PMTesting diodes with a leg desoldered from the PCB: what does it mean? If you don't actually pull that leg away out of the PCB, there is a good chance it's still making electrical contact.

I think it's time to have a conversation about your speakers. What is that head going into, a 2x12 or 4x12? Before opening and testing speakers individually, are you getting that nice sound out of all the speakers? What is the resistance of the cabinet reading? Does it pass the battery test: if you briefly connect the speaker cab to a 9V battery briefly, do all the speaker cones pop in the same direction? (Never connect speakers to DC for more than a moment.)

some explanations :
I tested all the diods with one leg desoldered AND away from the PCB, sorry, I didn't say it from the original post.

for the speakers, I burned the amp with another 4 x 12 cab than the one that originally came with the amp, (and I no longer have this cabinet), actually, it is connected to its original Crate 4 x 12 cab that I cross tested tested on another Head, and it's working perfectly, the Crate head have a similar issue on a Peavey 4 x 12 cab that i have.

Quote from: g1 on August 07, 2026, 11:33:05 AMTrim pot AP1 is the adjuster.

ok, i'll go and tune it tomorrow, but how does it work ? like a sort of "volume" ? may I have to take measures to make the adjustment ?

actually, to me, it sounds like the clean channel is louder than the two other channels, (at the same volume knob position), so it may be the way to go

PS, english is not my primary language, so please, excuse me if i'm not clear enough and don't mind asking questions if so 

Hey thanks man that was very generous of you to take the time to  offer that info I appreciate it

I need to start paying attention to impedance as it's obviously a major player in these systems

I was just reading about it here actually

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As G1 had me reading about it and this

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I did notice today that I had a pack of 741s also

The "butterfly-like" transistor pair arrangements, where one of them has the base and collector tied together are "current mirrors". The transistors are made together on the same substrated by the same fabrication process and have nearly identical VBE curves. And that includes temperature behavior, plus: the transistors are close together on the same chip and so thermally linked: one won't be hotter than another with a different temperature gradient of its VBE curve.

The VBEs of the current mirror pair are tied together, so whatever VBE is one transistor is the same on the other and that drives the collector current. This relationship causes the collector currents to be nearly identical (i.e. mirrored). By setting up the collector current in one half of the current mirror, the other half generates the same collector current.

The schematic shows several current mirrors tied together: Q8/Q9, Q10/Q11 and Q12/Q13.

The main purpose of current mirrors in amps is that current sources look like very high impedances.  It's like a trick for producing a very high resistor, that appears to be sitting on a high voltage. This is particularly valuable on a chip because it's hard to produce large resistors on a chip and takes up space. E.g. if we put a 1M resistor on a 10,000V supply, we would have a 10 mA current source. Provided we used the current source with loads much smaller than 1M, it would look stiff. If we make a similarly stiff 10 mA current source using transistors, it kind of looks like a 1M resistor on a 10,000V supply, in some ways. If we use that as a load resistor for an amplification stage, it produces a lot of gain. Using a current mirror (or other current source) as a load resistor is called "active loading".

You know like when you use a larger resistor for a tube plate, or BJT collector, you get more gain in the stage.  But there is a limit; the bigger resistor you use, the more you choke off the current. You can make up for that with voltage to a point. One problem with that is if the transistor shuts off, current stops flowing and then the full voltage appears on the transistor, which may not be rated for it. Active loads will never generate a voltage in excess of the supply. While within their limits for current regulation, though, they look like a giant resistor with a large voltage behind it.

These current mirrors clutter the 741 representative schematic, making it twice as "scary" as a schematic in which resistors play similar roles. Once you understand the mirror pattern, you mentally treat it as one unit.

You've done a lot of work and replaced a substantial part of the payload silicon in the amp, front to back: differential stage input transistors, output devices as well as the transistors in the foldback current limiter.

Testing diodes with a leg desoldered from the PCB: what does it mean? If you don't actually pull that leg away out of the PCB, there is a good chance it's still making electrical contact.

I think it's time to have a conversation about your speakers. What is that head going into, a 2x12 or 4x12? Before opening and testing speakers individually, are you getting that nice sound out of all the speakers? What is the resistance of the cabinet reading? Does it pass the battery test: if you briefly connect the speaker cab to a 9V battery briefly, do all the speaker cones pop in the same direction? (Never connect speakers to DC for more than a moment.)

Solid state amps don't mind volume. What they don't like is a shorted output.

Speakers can fail in a way that they first create a short circuit (voice coil enamel degrades from heat, creating shorts between the windings). Then during the failure episode, the coil burns through, so the speaker is found open. While some amplifier parts have failed also.

If, say, a 2x12 cabinet has one speaker that is disconnected or blown, the undriven cone acts as a passive radiator. But it's not in phase: when the working speaker moves out, the nonworking one is sucked in. That causes cancellation, particularly for bass. That's in addition to (or in subtraction to? ) the one speaker being 3dB less loud than two.

This worked pretty good and was easy to set up

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I couldn't get much separation 

Sorry for the strobe light display

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So starting changing out different capacitors and resistors trying to achieve lift off for channel two but despite my efforts they stayed close and tied up comingled like two fighters that the referee is constantly trying to separate 

The point of this I'm still not getting the AC vs DC thing so I'm trying to take a look at various aspects

This will be a good opportunity to maybe learn a few things

I wanted to modulate ? DC with AC or vice versa

So I got a 1500 ohm resistor and put some AC across it through a VARIAC and transformer

Got a nice little sin wave

Next I thought ok cool now it's time to add some DC and I can make the sin wave go up and down

Seems I forgot that a DC power supply will ground out AC 

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So I'm gonna have to think about this one for a while 

I think one thing I'm noticing is maybe have a small miniscule AC and a large(r) DC

Hmm oh yeah now I'm starting to recall seeing something like a diode clamping circuit

Might be time to check it out 

Quote from: carlsoti on August 07, 2026, 09:55:21 PMIf there's a trope about tube amp techs being too lazy or not thorough enough to be competent SS techs, I might embody that trope to the Nth degree. I seemingly tried every trick I knew to work through this one.

Oh , don´t be so harsh on yourself.
Fact is Tube technology was already mature and stable over 70 years ago, in the 50s, so if you understand and can repair a classic Fender amp, which can be repaired without schematic if needed, you basically can repair ALL Tube amps.
To boot, other makes basically clone a Fender, more o less. which narrows the field even more.
No such luck with SS ones, which keep changing, even today.
 

QuoteQ106, the TIP30B driver, was the only device that was soldered directly into the PCB, making it a "pull the whole board" job to test out of circuit. Once out of circuit, it STILL passed all the basic tests, but the gain was SO low. A new part arrived this afternoon and tested about 20x higher gain that the device I pulled. Dropped it in circuit and everything else fell into place. As one might expect, this Sunn is loud, clean, and relatively noise free.

Thanks again, to all who offered assistance.