Sunn Solos II problem

[jvm]

I have a 73 Sunn Solos II on my bench. Had failed output transistors. I've replaced them and the amp is working fine except that if I touch the chassis the sound becomes very distorted, no loss of volume , just a very nasty distortion. Both channels are affected. Same result when touching the strings of a guitar plugged into the amp. However, a cd player connected to any input plays perfectly clean and all functions on the amp work perfectly. I've cleaned all the pots, jacks and switches. The problem does not seem to be with a intermittent connection or component as I've poked, prodded and banged on everything. The amp works fine until I am connected to the chassis. Anyone have any ideas?

[drewl]

Is the chassis grounded, does it have a 3prong plug and does the plug ground have continuity with the chassis?

[gbono]

Input or output jacks now grounded (no fiber insulating washers)?

[jvm]

drewl, I've checked and cleaned every ground in the amp. Power cord is grounded. I've resoldered every connection in the ac circuit. I noticed that when I reverse the polarity switch the problem was worse. I replaced both .047 caps on the polarity switch. The problem persists in both positions but one is much worse than the other.

[jvm]

None of the four input jacks are insulated from ground. Both output jacks are. Schematic shows inputs grounded to chassis.

[glebert]

Does it do the same thing if you plug into the power amp input? Might as well figure out if it is preamp, poweramp, or global gremlin.

This has a "special effects" circuit, right? Could that be being kicked on by some sort of switching circuit grounding issue? Have you tried all the footswitch inputs, and does it act the same no matter if things are switched on or off?

Schematics here: https://forum.sunnstillshines.online...p?topic=4781.0

[loudthud]

Is there continuity between the power cord safety ground and the chassis? Is there DC across the speaker? Note the unusual bridge drive power amp with a floating power supply. The driver transformers in these amps are prone to developing shorts and this puts DC across the output. The only known replacement for the driver transformer is from Mercury Magnetics and is very expensive.

Schematics can be found here: https://forum.sunnstillshines.online...p?topic=4781.0