Dano Centurion problem

[drewl]

Got a Dano 272, similiar to the 275 schem below but no reverb.
I'm getting DC on the volume pots, but it's coming from the following PI stage.
The preamp is seperated from the power amp, with a shielded cable connecting the two 330K wiper resistors, when I remove that cable the DC is gone from the pots.

Pretty sure I need to change some of those .01 PI coupling caps, as that stage is compressing/acting funny.

Any idea why dc is coming from that PI input grid?

[52 Bill]

Any idea why dc is coming from that PI input grid?

Bad tube?

[drewl]

C'mon, you don't I would have checked that?

Anyway, it's alot like this schem here.
Notice the 1Meg they added. I tried it and it seems to have done the trick.
That's checking it with no preamp (left it at home) Maybe those resistors drifted up or the cable between pre/power amp is flaky.



Anyway that stage looks good now, the output tubes probably need replacing. They compressing when driven hard, cutting out almost.epiphone_dano_century30_1961.pdf

[Enzo]

Those PI grids can build up a small DC voltage charge from accumulated electrons. That is the basis of "grid leak" bias.

[drewl]

It was going up to like 4 volts sometimes, it was the cable. It was flaky and corroded.
Hmm, that and found a couple more of the old brown 50uf paper caps were dying under load and everything is sounding great now.