DC-3 red plating and squealing

Hi so I'm new to this forum, but have always been a fan of Mesa amps! So my DC-3 that i've had for about a year or so has recently started making a squealing sound (both channels) and two of the EL84 tubes are red plating(from looking at the back the two on the left). I'm pretty new to troubleshooting amps, but my friend is pretty good with it. We checked to see if it was any of the preamp tubes, but they seemed to be ok. Pretty much when you turn on the amp it starts squawking loudly, and if you tap around the amp it amplifies the problem. He though it may be a solder joint going bad for one of the power tube sockets. From my eye it looks like the solder joints are fine. I tried further localizing the problem, but it seems like I am running in circles. No matter where I tap inside the amp the symptom seems the same. Does anyone have some insight into this problem?

Thanks

Welcome to the forum!

I am sure it's the two EL84's going south, it's time for a retube (power amp) double check the preamp tubes to be safe.

I'm surprised he didn't tell you to swap those out (EL84's) for new ones.... :?

How old are those EL84's? Have you tried a new set? I would think that's the place to start. If new tubes don't help, I reckon you'll have to take it to an amp tech. And you'll have a backup set of tubes. Let us know what the outcome is.