DRRI Bias Issues?

[retrorod]

Hi, Hoping someone can help me troubleshoot!
I am working on a DRRI. I understand most of bias supply as it pertains to the older hard-wired type amp boards. On this amp, I am not getting neg.voltage to the control grid(pin5) of the pwer tubes. Turning the 10K pot adjustment makes no difference in the reading. Should I suspect a bad resistor or capacitor in/near the bias supply? The 10K pot reads good. The diode reads good (continuity in one direction) There is a 22 ohm resistor (R69)that is parallel to the diode that reads kind of funky? None of the resistors appear scorched.
I was told that the OTubes were changed and were ran extremely hot and eventually blew a fuse and maybe took out the rect. tube.
If anyone is familiar with these amps technically, I would be greatfull for some hints on specifics to measure and troubleshoot. I have downloaded the layout and parts list, so referencing to the #'s (R& C) would help alot.
I will look for replies and can give additional readings if needed...Thanks, Rod

[Blue Strat]

Take voltage measurements at the pot or components connected to it. If the pot doesn't have any negative voltage on any of the leads there's an open connection or resistor feeding it.

The circuit is identical to hard wired DR's.

[mbratch]

There is a 22 ohm resistor (R69)that is parallel to the diode that reads kind of funky?What does that mean? ;)

You'll need to disconnect one end of some components to get a reliable reading. But checking the components about the bias circuit is the right thing to do. It should be very similar to the old amps. The schematic is available at the Fender web site if you haven't obtained it already. Use that as your guide for what to check.

[retrorod]

Just an update. It turned out to be the 22 ohm res. that was reading kind of funky(open). It was in line with the diode. Replaced that puppy and BAM! Instant fix! I like it when a plan comes togather! Thanks for your support...Rod