Hot Rod Deluxe issue

[Speedsense]

At a gig two weeks agp, my Hot Rod was making a low crackling sound, like rusling paper... then the power started to go in and out as I was playing and breaking up on the clean channel. I switched channels and the same thing was happening.
I shut the amp off and played through another the rest of the night.
I decided at home that it was a tube problem and switch out the power and pre amp tubes. It seem to be working fine and thought I'd fixed it.

The next gig when I turned it on and played it, it was fine, though still the crackling noise, I left it on and played the first song with more dropping out of the volume (it would cut out to low volume, cut back in to adjusted volume.

A friend who taught me how to work on my amp (I've fixed issues before, like the 5 w channel switching resistors.), suggest a routine of turning it on until the problem happens and go from there with his suggestions.

However in doing this test, as soon as turned the amp off of standby, the tube closest to the pre amp tubes (V4) had a glowing red stripe down the middle of it and the amp sounded a blasting noise of low tone squealing.

I have read in the forum that it could be A) the plate resistors or B) the bias circuit or C) the soldering joints on the tube holder.

The question is do I replace R61, R62, or are there other resistors that I need to change.
Secondly, I can't figure out which resistor (s) to replace in the Bias loop or where it is in the diagram. (Don't know the symbol for the adjustor)

The solder joints were freshed up a couple of months ago.

Thanks in advance for anyone's help

[Billy R aka DynaFreak]

it sounds like you may have a problem with the negative bias voltage on one or more power tubes. After checking for presence or absence of bias voltage at pin 5 on the pwr tubes, I would look closely at the solder joints on the pwr tube sockets, especially pin 5 where the bias voltage and signal is applied. An intermittent connection there could cause the symptoms you describe. In any case, after inspection I would go ahead an reflow all those solder joints and add a little fresh solder. Some of these amps come from the factory with a bare minimum of solder on the pwr tube socket connections and a little touching up helps, especially in an amp that is gigged often. If you still have lack of bias voltage at pin 5 you will need to trace the bias circuit. I recommend you do that rather than just start replacing resistors. Another hint for these amps is that the bias filter capacitors (C38 and C43) tend to vibrate loose and cause bias problems.

[Enzo]

First suspect is the tube itself.

As long as you are inside look CLOSELY at the solder on the power tube socket pins. Any small cracks? I resolder those routinely.

Aside from that, first thing I;d do is try different power tubes. Or at the very least swap places with the ones you have. If teh same tube in the new socket still ge4t red hot, it is a bad tube. If the other tube now gets red hot in the socket the first tube used to be in, then the socket or amp circuit has the problem.