Unusual Hum/oscillation

[Mark]

Glad the amp is fix. So the 10K resistor went to the input?

If so I would have stuck it in anyway when making the amp.

[RockinRocket]

Yep on the input. I don't start with the grid resistor so I can see how close to stable the amp is first.

[Littlewyan]

Very odd. Glad it's fixed though . Where did the 10K grid stopper go?

[Mark]

On the input.

[RockinRocket]

Yes on the shielded wire input.

I'm still going to track this down with out the gridstopper. My curiosity needs to know why.

I'm going to remove the bright switch and do a normal 500p on the pot to see if the switch was picking up oscillations.
It could be the wires run from the TS on the chassis floor fairly close to the switches micas. Its laid out wire for wire as per Francesca.
Latter amps such as Ingrid and Kitty have the wires run away from the bright switch.

[pompeiisneaks]

As I understand it from reading posts here and about Ken elsewhere, he had to occasionally add grid stoppers as well, but it just depended on the amp. The general design consideration of all the Trainwrecks was that he put them right at the limit of oscillation, blocking distortion, etc to get really raw tone out of it, and then just barely dialed it back enough to not let those things happen. He had a basic design, built them, and then tweaked a few parameters to settle them down.

It sounds likely to me that grid stopper is just going to be needed for your particular amp. In my general understanding anyway.

~Phil