Help-Tube Problem. How do you test a tube socket?

[MJ Slaughter]

DC-10 head one of the inner power tubes, closest to the input jack, has blue flashes and at that time I hear kind of a poof sound from my speakers. Doesn't happen right away but after a minute or two. Tried a different set of tubes with the same problem. Never noticed it before because I usually run in 60 watt mode and that only uses the outer tubes but recently I've been using the 100 watt mode.

Since having that problem I've been watching my tubes as I play looking for any other hint of trouble. In the 60 watt mode when the master and level are around 5, halfway up, the outside power tube closest to the input jack glows brighter as I play. At one point it became so bright I thought it would blow so I stopped. The other outer tube stayed a constant orange and didn't seem effected like the other.

When playing with the master and level around 2-3 I don't have any problem. I imagine that's because I'm not pushing the amp as hard. I am using an attenuator so I don't hurt my ears any worst than they are. A local tech I called said it might be a tube socket but he can't get to it until Tuesday so if anyone can assist I would sure appreciate it.

 

[acorkos]

sounds like you may have a problem with one inner and one outer socket, or maybe the sockets are ok and the tubes are going bad.

focus on one problem at a time. stay in 60 watt mode. swap the outer 2 power tubes and see if the bright orange glow remains with the socket, or moves as you swap the tube. if it moves, then the tube is bad. if it stays on the same socket, then the socket (or more likely one of the associated resistors) is bad.

once you correct that problem, switch into 100 watt mode and do the same tube swapping with the inner tubes.

hopefully, your amp is fine and all you need is a new matched quad of power tubes.

 

[MrMarkIII]

Try un-plugging the attenuator. They wear tubes out faster. Seriously. They do.

 

[Tuna141]

One of the tubes may be going bad. Try swapping the pair for some new ones or swapping the inner with the outer pair to see if the problem follows the tubes.