DC-10 Power Tube About to Blow?

[MJ Slaughter]

When my channel masters are turned up around 5 or more and I'm either hitting the front of the amp hard with an OD pedal or engaging the GEQ set for a boost the power tube closest to the input jack glows to almost red then white/blue and I hear crackling coming out the speakers. I've already swapped all the power tubes and it does it in both 60 and 100 watt mode. With the channel masters down around 3-4 and the main level cranked all the way up it will do it to some degree but not as much as with the channel masters up. I use an attenuator so no, I'm not blowing my ears out, I hope. :lol:

I had this problem a few months ago and took it into a tech who found a burnt resistor near that tube's socket. I/we figured that to be the problem and I hadn't noticed any other trouble once that was fixed until this weekend. I don't usually play with the channel masters turned up much so I guess it wasn't a problem until now. That same resistor isn't burnt yet. It's not that I need to play that loud but I want the amp to be reliable and this doesn't seem like anything I should have to put up with. Until this is fixed I just won't use the attenuator and keep my volumes down.

Any suggestions or tips would be greatly appreciated.

 

[MJ Slaughter]

Update:

While the wife was out of the house I tried all the above without the attenuator attached. Though it was crazy loud, even with pillows and blankets over the cabinet, the power tube did not act up. All settings where identical with and without the attenuator installed yet it only acts up with the attenuator. Do you think there is something wrong with the attenuator and why should it cause any more strain on the amp than just having the volumes turned up high?