Do not assume transistors you already installed are OK.  ANy time ther is a circuit fault, the new transistors may have been damaged - and wiring them backwards certainly counts.  All around all those transistorws are various resistors.  Many times when transistors short out, they take out resistors with them.  SO check all the resistors in the output section for opens.

You may be right JM, an alternative might be that he doesn;t know how much power is being delivered for a given loudness.   For example, "Gee, this is pretty loud."  But is it 12 watts or 50?  I guess just to orient myself I might monitor power levels to get an idea how loud the amp can get before crossing into too much power for the speakers.   That is a real oversimplification of the system, but maybe that is his plan.  Once you know how loud 90 watts is, then you can try to keep the amp less loud than that.  Of course that assumes your "hearing memory" is up to that task.

I fairness, I don't think the little short 8 series reverb pans sound as good as the larger ones, which will drop in their place electrically.  Only issue would be whether there is room inside the cabinet for the larger pan. 

Yes it is a complex amp, but when the problem is NO sound, I think there is a lot of checking that can be done without the prints.

While they do fail once in a while, transformers are the LAST thing on the suspect list.  If power is missing to the power amp, it is way more likely to be an open fuse, a broken solder connection, and open resistor, etc.

The direct out works?  In BOTH pre and post settings?   That means preamp is OK.

Is signal present on the master volume control?  and on its wiper?  Is it getting to the power amp board?  Is there signal on pin 1 of the PA input connector?  Is there signal on R19 on the power amp?

I assume we have tried different speakers and speaker cords.

Is there ANY sound in the speakers?  Any little thump or pop at power on/off?  ANd little background hum or noise, or other sign of life?

Is there V+ and V- on the collectors of the power transistors?

I have to point out that the service center may have no idea what the specs are, even if they wanted to tell you.  My shop is an authorized warranty repair facility for most of the major amp brands - though not Line6 - and frankly I have no idea the specs on most any transformer I see.  If I determine a Peavey 5150 needs a transformer, I call Peavey and order one.  If I need a transformer for a MArshall TSL100, I call MArshall and order one.  And so on.  Knowing how may amperes of how many volts doesn't enter into the repair picture.

I am not stressed out by this, Jack, I am merely trying to determine if we are calling things by different names.

Semantics?  Well yes, if we are not all using the same definition of clipping then it will be difficult to agree.   In my world clipping is a classic term meaning the removal of the waveform beyond some certain amplitube away from zero.  In other words lopping off the tops of the waveform.

I don't consider slicing out part of the waveform at zero crossing but leaving the larger amplitude portions of the waveform to be clipping.  Distortion, yes, removal of part of the waveform, yes, but not "clipping."

If someone else uses the term clipping to refer to the removal of ANY part of a waveform, well there is our disagreement right there.

Didn't the article state that the preamp was custom made for the testing?  As opposed to using a commercial preamp.


Interesting paper, I'd note the preamp testing was limited to "linear" settings, meaning I guess that it was only tested running "clean."  Thus no attempt to compare overdriven preamps.

Go ahead and try different 12AX7s in the amp.  It might be interesting to find out how much difference the band makes, and again maybe how little difference it makes.


It certainly won;t harm the amp performance to install fresh caps, it is only my personal opinion that it probably is not necessary.

I agree, a 12AX7 can last for decades.  The preamp tubes generally do not wear out the way power tubes do.  They can fail by going noisy, getting microphonic, just not working at all, heater burning out, etc.  But unless one of those things happens, if it sounds good, I'd leave it.

And really, 10 years old is not all that ancient for your filter caps.  FIlter caps of that era were better parts than filter caps of 30 years ago.

I am following the circuit, are we looking at CR1, CR2 in the Triumph?   This is the same noise reduction circuit Peavey has been putting in many of their high gain amps the last 20 years.

The two diodes are in series with the signal, hard to clip in series.  Clipping diodes are generally across the signal path, not in series.  Or in the case of op amp related circuits, in the feedback circuit.  COnsidering the fairly strong signal at that point consider what the diodes do.  The need to have about half a volt across them before they conduct.  Noise in the signal tends to be a lot smaller than the signal itself.  SO until the signal waveform gets over that half-volt threshold - and in either direction since ther are two diodes cross wired - the signal doesn't pass.  Once the waveforn exceeds that junction potential, then things flow as normal.

That is not clipping.  What that is is slicing out a little bit of signal at the zero crossing.  It introduces a slight crossover distortion that is almost impossible to hear in the distorted overdriven signal.  But in so doing, it also slices out the majority of noise.

Look at the circuit for the PV JSX.  The same two diodes are there as D1, D2.  But in that amp they added a 1 meg pot in parallel with them to dial in the amount of effect they have.  That control is named "Noise Gate."


And at the risk of tooting my own horn, I have worked on a few of these myself in the last 24 years of running a Peavey authorized repair shop.

40 what?  Ohms?  Millivolts on diode test?

That is a JFET, it is ON until you turn it off with voltage at the gate.  SOurce and drain are interchangable, and have a low resistance between them.  I usually expect maybe 100 ohms, but who knows.  Since the source and drain are more or less connected together, the gate will act like a diode to them.  SO until I know what you were measuring, so far it sounds OK.

But the bottom line is this, with Q12 removed, does the amp now work correctly?

Yes, those zeners can get pretty darn hot.

Why are there two names?  Why do I call it "Germany" and the folks there call it "Deutschland?"

ECC83 is the European numbering system label for what we call 12AX7 in the USA.  Look at the page in the RCA tube manual, it says "12AX7/ECC83."

All the wondering about odd tubes that EC83 might mean aside, I am pretty sure you mean ECC83 - two Cs - as that is a common tube.  And if you google ECC83 instead of EC83, I bet you find all manner of 12AX7 information with it.


Now there are tube marketers like Groove Tube that make "both" 12AX7 and ECC83, but what they are doing is trying to come up with different names for each of the 12AX7 varieties they sell.   They are all 12AX7s.

D7, D8 are 5w zeners and they normally get pretty hot.   Hard pressed to think of any other diodes that would get hot.

Q4 has only 122 ohms between B and E in circuit.  Same with Q9.

It's a long shot, but just remove Q12.  it is a mute at the input.  If it is bad, it can mess with you, otherwise we don't need it until we are done here.

Q8, Q3 are limiters.  Try removing them.

Is Q1 shorted?

What is the nature of the distortion?  Do you have a scope?