I've got a amp that keeps blowing a tube. The amp is less than 2 months old. I'm keeping the manufacturer's name quiet at the moment because I am in the process of dealing with them about this issue and giving them the chance to make this right. The tube it keeps blowing is a 12ax7 that controls the reverb. I can put in a new tube, and the reverb works for 5-15 minutes, and then suddenly the reverb goes out. The tone of the amp does not change in any other way - the reverb just goes out. So far it has gone through three tubes in one day. When I contacted the manufacturer they suggested replacing the tube, and it blew. When I got back to them on this they said try it again because if the reverb comes back it must be the tube. Sure enough, a new replacement and it blows again. I'm curious if anyone might have an idea of what might cause this?