Fender HD deville no sound in drive channels

[pontiacpete]

This amp works fine in the clean channel but when switching to the drive channels it is silent.
The LED turns on to yellow and red when pressing the more drive switch.
With the ohm meter I'm am able to see that both relays are doing some switching but I'm not sure if they are switch completely.
At TP 13 I'm am not getting anywhere near 510mv. This is AC right?
I'm wondering how do I test the 2 zeners CR1 and 2 and how to check the JFET Q1 and 2?

[Tone Meister]

What schematic are you looking at Pete? The schematic I have for the earlier Hot Rod Deville shows 1.51V AC at test point 13 and the Hot Rod Deville III schematic shows 1.82V AC at test point 13.

Have you tried another 12AX7 in V2 yet?

[pontiacpete]

Thank for pointing that out, I was looking at the blues deville schematic. Wrong.
I'll try the TP again.

[pontiacpete]

TP13 reads 4.2mvac when in clean channel and 3.4mV when in drive.

[Tone Meister]

What do you have at TP10, TP11, and TP12? Might be worth the effort to try another 12AX7 in V2. The V2B triode provides the gain for the Drive channel. You just might have a dead plate in that tube.

[pontiacpete]

Thanks Tone Meister for the heads up on V2 and it's function. I had changed the tube and have plate voltages on both plates. While probing around the drive channel came on.
I think it is a connection issue, perhaps the socket or the ribbon connector.
I'll be back with that info
thanks again!

[Tone Meister]

Glad you're on the right track. The problem could have been just dirty and/or loose pins in that socket. Any time I am inside any of these amps I always: 1) re-tension and clean all the socket pins, 2) re-solder every tube socket on the tube board, 3) clean the PREAMP OUT and POWER AMP IN jacks, and if there is a reason to peel back the tube board, I always swap out R57 and R58 with 1/2 watt metal films because they are all potential points of failure.

[Tone Meister]

If it's not socket or tube related, another thing to check is the solder joints on those relays. A few times I've seen fractured joints there keep the following circuit from responding to a relay that seemed to be switching fine. Of course, you'll have to peel the main board back to see.

[pontiacpete]

When the amp came in there was no sound on both channels. I found R57 opened up so with the socket PCB out I re-tension the sockets because the owner said V2 was falling out after playing a while.
I pulled the socket PCB again and decided to change the V2 socket. Removing the solder I found 2 pads disconnected
from their traces on pins 8 and 9.
New socket in place and both channels are working.
Thanks for the help Tone Meister!!

[Jazz P Bass]

The newer Fender amps seem bent on using single sided boards.
Single sided boards suck eggs in tube amps.
Traces lifting, pads cracking.

The whole point of double sided boards is that they are durable.

This point seems to have eluded the bean counters at Fender. (a raw single sided board is more economical to produce).

[Tone Meister]

Good news indeed Pete and good catch. Yeah, the new Fender stuff could really benefit from a sturdier PCB that's for sure. It definitely takes a delicate touch to work on a modern Fender without curling a trace, or worse.