Blues Deville Repair: Bias issue

[Steelwitch]

Hey y’all, I have a blues Deville reissue up on my bench that came with a redplating 6L6 (V4)— the 1R cathode resistor and in4006 were both shorted. After replacing them, the maximum bias I can get is 40mv on the test point. There may be a bad connection on the v4 socket. When it’s nudged slightly to the right the bias goes way up and it’s starts to redplate— there isn’t anything I can see that would be causing this to happen. Any suggestions for things that might have failed besides the tube socket? Thanks! Here’s a schematic:

https://www.thetubestore.com/lib/the...atic-Rev-A.pdf

[Enzo]

Resolder all the pins of the power tube sockets on their circuit board.

[nevetslab]

Hey y’all, I have a blues Deville reissue up on my bench that came with a redplating 6L6 (V4)— the 1R cathode resistor and in4006 were both shorted. After replacing them, the maximum bias I can get is 40mv on the test point. There may be a bad connection on the v4 socket. When it’s nudged slightly to the right the bias goes way up and it’s starts to redplate— there isn’t anything I can see that would be causing this to happen. Any suggestions for things that might have failed besides the tube socket? Thanks! Here’s a schematic:

https://www.thetubestore.com/lib/the...atic-Rev-A.pdf

It sounds like the bias pot itself is either damaged, or on the foil side of that PCB, you have a solder joint fracture. I've had these pots go bad...often from having to break the red glyptol that locks the pot at a specific bias setting from the factory. With the amp still in Standby, measure the bias voltage range at the wiper of the bias trim pot (those are the rear support terminals on both sides of the dial). If there is a sudden jump in bias voltage, instead of a smooth continuous variation of negative voltage, then either the pot is bad, or there's a connection issue on the control's feed to R59/R60 where the bias voltage feeds both input grids to your power tubes. (Bias is ALWAYS present even in Standby mode).

[g1]

When it’s nudged slightly to the right the bias goes way up and it’s starts to redplate— there isn’t anything I can see that would be causing this to happen.

When you nudge the socket, or when you nudge the bias pot?

[g1]

As far as not being able to get the bias over 40mV at the test point, do you have proper voltage at pin 4 of both power tubes?

[Randall]

"the 1R cathode resistor and in4006 were both shorted. "

What makes you think the 1 ohm resistor was shorted?