Dual Rectifier channel 3 problems, ideas?

[Choop]

Hello, I own a Mesa Dual Rectifier 3-channel head, and there seems to be a problem with the channel 3 setting. Lately when I switch to this channel, it plays as it should for about a minute or so, and then a very noisy cutting out kind of sound begins to happen. The signal is well, cutting out, and it's very fizzy, kind of like when you have an old instrument cable with a loose solder. It looses all of it's gain and perceivable power. I know it isn't tube related because the head recently went through a full retube and the problem still persists. Would anyone here be able to tell what the possible problems are from my description?

 

[fluff191]

Time for a retube.

 

[Choop]

Time for a retube.

I said in my post that I just recently gave it a full retube, yesterday actually since I'm posting at 1:29 am here. It still does the same thing, and only on channel 3.