[quote author="Wavebourn"]
Yes, they have both a pot and a switch on output, so in some position of a switch and a pot anode is connected to ground through a cap and low resistance of a pot, so current flowing through ground creates a voltage drop on HF enough to cause oscillations.
They have only one ground wire going to PCB (though, on the schematics they go from 2'nd triode to switch then to the pot, then to the 1'st tube, etc...), if your version is close to what I've seen.
I mean a socket through which the output chassis is connected to a preamp section. Is it separate on your amp?
That amps I've fixed had such a problem, so I decided to share my experience with you.[/quote]
Ok. I understand the 10k resistor now. that makes sense.
as for the ground... the ground from the preamp board goes to the output tubes pin 8, and then that wire goes to the negative terminal of C17 and then grounded to J6 (the speaker output jack)
there is Also the ground wire from the tone control pcb. that goes to the preamp pcb. There is only one wire, it goes to the preamp board.
does that sound right?
on my vt-22 there is no socket that connects the powertubes to the preamp board, they are connected to the preamp pcb by wires. soldered directly to the board.
perhaps you are thinking of the newer V4 that SLM makes? or confusing it with the SVT?
would it help if I posted a picture of the insides of the amp?
thanks alot for all the advice, I really appreciate your help on this.