SF/BFVR Channel 2 peak distortion

[Clearspider]

On Channel 2 of my SF BF'd Vibrolux Reverb, I have a distortion that is engaged only at peak signals. Like, if I rake the strings I get a momentary high-gain distortion that quickly levels off. It happens at high amp volume.
I noticed that certain PI 12AT7s will control it, while others don't.
12AX7 in the PI will surely let it happen.
Certain tubes in the preamp let it happen (hi-gain RCA, Pro/Comm relabel) while a Mullard 12AX7 will better control it (unless there's one of the 12AT7s in the PI that allows it.)

Also, I have not replaced the pull-boost volume pot and wonder if somehow it is letting it boost at high-signal... somehow. Sound dumb?

Could there be a bad solder joint after the PI that rattles out at high gain?
If so, I can't figure out why it's only on Channel 2 but the PI tube has the greatest effect on the effect.

[TheAmpNerd]

Can't get peaks eh?

Filters been changed?

Tubes test okay?

[Clearspider]

The filter caps have been replace, none of the others though.

[Clearspider]

How can I rephrase this to get some possible solutions?

[DanD]

How can I rephrase this to get some possible solutions?

I know folks who refer to fenders with a irritating peak as having that pissed off sound. It's a non-musical distortion on top of harmonic distortion.
I heard a black face Pro Reverb that gave it up like that.
It wasn't pleasant close up but from a distance it gave the amp a certain unique character.
Have you listened to yours from a distance?
Hope that helps.

DanD

[Clearspider]

No, but I don't know if I'd like it. It sounds like there's some tiny animal in it that gets very angry when you rake the strings to hard. It yells at you then goes back to sleep.
I just want to fix it, cuz it sounds wrong.

[Blue Strat]

How can I rephrase this to get some possible solutions?


Did the amp do this BEFORE you modded it? If not, there's only one thing to do...demod it and start again....step by step, testing after each change. Apart from that we'd be totally guessing. As of now, we don't even know if the work has been done correctly, what the status was before the change, status of the tubes, etc....so it's like asking someone to do open heart surgery over the telephone:)

[Clearspider]

Well, not necessarily. I was wondering if by my description, someone could say, "Yes that would be ..." or "Does it happen when (scenario)?"
It's happens at such a specific action that I thought it'd be common or easy to diagnose, as it's one of the most popular amp designs ever.
The amp, as far as I know, did not do this before the mod. However, I did not play it very much before that, so I couldn't tell you.
As far as the tubes go, like I said, the PI has the most say in whether it distorts or not. The rest of the tubes seem to have a negligible effect. So I wonder if it is something like a cold or broken solder joint after the PI which only malfunctions upon encountering a very strong signal. Then there's the fact that it's only on Channel 2. So maybe it's a bad resistor in that signal path? I don't know enough about amp repair to diagnose by description but it seems like it happens every day here. I do know enough to not kill myself, so I feel comfortable with suggestions.
Chopstick?

[Blue Strat]

An intermittent connection is always possible and can show up in any number of ways. Try the chopstick method, re heat all solder connections, wiggle the tubes in their sockets and see if that produces any crackling, and FIRST OF ALL, clean all sockets and tube pins.

Measure all voltages and compare them to the schematic.