Dual rect. in distress

[Coraje]

i own a 2 channel dual rectifier... which i bought used ..
i havent had any trouble with it till now .. whenever i use it for around two hours sound stops coming out of the channel im using ( the red one). this would never happen before.

i thikn its something in the preamp . kause when i use a effects pedal as a Pre ... the amp sounds again ...
usually when it kools off it'll start sounding again on its own without a pedal..
anyways i live abroad so there is no mesa store or support here .. and id very much appreciate some advice

 

[Hopkins-WitchfinderGeneral]

sounds like a blown or nearly dead tube. You should look at replacing all the preamp tubes.