Fender Hot Rod Deluxe- Cutting out and dirty

[llahwerd]

First of all, I don't really know anything about how amps work, so if anyone responds, please put your response in complete layman's terms. Here's the problem with my hot rod deluxe: The left power tube does not glow. All other tubes do. Both the clean and distortion channels sound extremely scratchy and terrible, and sometimes they cut out completely. There is a pretty loud humming noise, which does not go away if the volume is turned all the way down, and it happens whether there is a guitar plugged in or not. When it's on standby, there is no hum. I did the "pencil test" on all the tubes, and none make any noise, so I think they are all doing ok, except that the left one isn't getting any power. So what should i do?

Backstory: I've had the Hot Rod Deluxe for probably 5 years now. About a Year ago the sound started to go, so I had the tubes replaced at a shop. It worked for a month or so, and it started to get shitty again. I took it in again and got it repaired, and it worked for a few days. I forgot about the amp for a long time, I'm deciding that I want to fix it now.)

[JoeM]

Did you switch the power tubes and see if it's still the tube in the left socket that doesnt glow?
Try plugging a cable in the power amp in and preamp out jacks. Maybe the cutting in and out is a dirty contact. There's other possible causes, bad solder joint etc, but try these first.

[CharlieP]

Time for new power tubes before you fry something else!

[llahwerd]

New developments

Ok, so i found a bad solder on the left tube, so i resoldered that and now both tubes glow. I'm still getting the same terrible sound, all dirty and ugly, but it doesn't completely cut out anymore. I highly doubt my tubes are bad, since I only bought em a year ago and have barely used them, but i guess it's possible. JoeM, do you mean plug my guitar into the preamp out jack? or what? Please explain. (sorry if these are stupid questions, haha)

[JoeM]

Ok, so i found a bad solder on the left tube, so i resoldered that and now both tubes glow. I'm still getting the same terrible sound, all dirty and ugly, but it doesn't completely cut out anymore. I highly doubt my tubes are bad, since I only bought em a year ago and have barely used them, but i guess it's possible. JoeM, do you mean plug my guitar into the preamp out jack? or what? Please explain. (sorry if these are stupid questions, haha)

Not into the preamp out. Just a guitar cable plugged into the pre-out and power amp in. There's contacts that might be dirty. You can plug into the power amp in, the tone controls etc wont function, but if the noise/cutting out stops, you know it's somewhere in the circuit before the power amp.

[Jazz P Bass]

O/K. You found one bad solder joint.
Reflow all of the power tube solder joints.
If you feel up to it, the main board should be removed. (a real PITA)
Resolder the big 5 watt cement resistors.
For that matter, reflow all of the big components.
Especially the power supply caps.

[llahwerd]

Still Dirty

I plugged into the power amp in, still dirty. I also plugged a cord into the preamp out and power amp in, still dirty. So does this narrow down the problem some?