I've got a 63 Fender Concert that blew one of the power tubes after only a couple hours of use. Had a tech replace the tube socket, the resisters at the socket, and new power tubes. After a couple hours, same thing, started to sound really hot (good!) and saw that the tube was glowing badly and shut it down. BTW, the amp had been in an attic for about 30 years. Any help would be greatly appreciated!