DSL 401

[Valvehead]

I powered it up tonight , removing 1 transistor , out of the amp 1 at a time for signal , then replacing it....next one , replacing it , etcc T9 - 10 - 11

Nothing--no OD channel .

Im so close......and so frustrated .

tested each of the 3 J174 , out of the amp and on the bench for resistance and Diode test---all 3 are identical .

[DrGonz78]

Did you suss out that T11 issue and do the voltages make any sense now? So we have no signal on OD channels. Perhaps you have all the channel switching circuit running fine now. Have you tried to replace V2 to make sure it is not bad? Just a quick thing to check or at least to make sure you have checked it.

Edit: Or do I have that backwards and V1B is the tube used to generate the Overdrive in the amp? Perhaps it is V1 since I see ODMUTE at that tube.

[g1]

Agree with Dr. Gonz that the fet switching cirucuits seem to be working properly. Time for signal tracing.
You hear the relay click, but are it's switch contacts closing and passing signal?

[Valvehead]

FOUND THE PROBLEM !!!

What a F$!$@@#! n relief............ !!

i went back thru the preamp area with my meter and magnifier , triple checking connections---finally found a bad one....looks like someone replaced a 100k in there previously , and it was just barely on a bent up trace....so i soldered and Bingo---------------amp works perfect now !!

I appreciate everyones time and knowledge and I definitely learned a little about the J174 !!

THANKS GUYS .