Fender Stage 165- Something I have never seen in 40 years

[kscience]

Enzo, Juan, anyone-

https://www.facebook.com/5oftscience...9352513041925/

This is the low voltage dc supply post 82 ohm resistors; i have the output devices out and no hv even hooked up. Trying to find a nasty buzz after a friend gave it his best shot. There is distortion on the positive rail ripple that sure as hell is the buzz.

I unhook the zener droppers and of course its gone. looked at the current on both, one at a time; 120 & 119.5ma, so they are balanced.

WTF???? Anyone ever see this before?

[kscience]

Oh, and its not the zeners. They as per usual ruin the phenolic pc board so i always take em out and mount ones we make on the chassis; the wires between do not carry the heat back to the board. Betwen these fenders [m80's, stages, etc] and ampeg ba115's we have the system down. do TO-220 zeners; the npn does the - one, pnp for the positive so they just screw directly to the chassis, no isolation needed.

no difference.

It is as if one of the op amps is arcing internally or something. Damndest thing. They use Vbe multipliers for bias voltage references, too; Dad suggested its easy to do this and not have to carry a ton of zeners in stock.

[g1]

Is this maybe a 185 ?
Have you checked the main filter caps for bad solder in case you have a problem before the dropper resistors?