Super reverb screeching noise

[DesmondWafers]

Bad day today, I can't turn my super reverb on without a terrible screeching noise. Even with all the knobs at 0 and nothing plugged in, it still happens and it's LOUD. I'm assuming it's a bad tube (I haven't moved it around at all recently or anything) but I don't know enough about these old amps to just start pulling tubes and turning it on haphazardly. I know some of you guys are experts so any help would be appreciated.

[Racing]

One thing you CAN try yourself is pulling the phaseinverter tube.
Huh?
Yeah. Take the rear facia off. To the left there will be larger tubes. These are your powertubes. Then there will be like small aluminium "cans". These are springloaded shields for the smaller tubes,and you´ll notice there´s several of them (if they´re still in place)
These shields are fastened by a bayonet setup. Press gently towards the chassis and turn and they should come right off.
Now.
The small tube,with a shield,closest to the powertubes is the phaseinverter. Off with the shield and then pull the actual tube downwards.

Start the amp up. If it still squeels then the issue is your powertubes and these needs to be replaced. This needs to be done by a tech as bias needs to be set for the new ones.
If the squeel is gone...that´s simpler as that means that it´s one of the preamp tubes that has gone ape. There´s two types of such in there. ECC-83/12AX7 and ECC-81/12AT7. The latter being the phaseinverter tube.
These tubes you can replace yourself. Just yank the old one per above and shove a fresh one in there.

This "modus operandi" can be used all the way through the preamp tubes. Ie;you can not hurt anything as long as you just make sure that the small tubes gets reinstalled in their right position. They keep 9 pins and thus should corespond in that manner vs their sockets. Need be lay the amp down on the floor "belly down" to be able to see how respective socket is installed.
You do NOT need to replace them all. One at a time is just fine. Do so,in such a scenario,until the squeel goes away. Ie;ONE 12AX7 goes through the entire series of them...one by one..and ONE 12AT7 replaces the phaseinverter.

What´s what is printed on the glass of each tube.
Some tubes might also say 7025. These are ALSO 12AX7 tubes. Just less microphonic and less hiss.

[DesmondWafers]

Thank you for the help! No luck on the phase inverter tube. I pulled the power tubes just to look at them and one of them (the one closest to what I believe is the rectifier tube) has melted the little foam rings on the tube. I wonder if that means anything? I just had these tubes replaced less than a year ago as well, so quite a disappointment.

[Racing]

Foam rings?
Huh?
Can you take a picture?

[DesmondWafers]

Not mine, but same thing. They weren't THAT melted, but pretty bad. Just on the one power tube. When I bought the amp 7~ months ago, there were some problems with the old power tubes so they swapped and biased them for me. They also put those rings on, I just left them.

[andy_tchp]

Yikes. They should be silicone, aren't really necessary, but that ^ shouldn't happen either way.

Guessing that one power tube failed in a terminal fashion and starting generating SERIOUS (beyond the normal level of 'burning @#!*ing hot') heat