So my DSL 401 has been giving me fits for a while now and i cant get it figured out. The amp has had the br changed and is raised off the board with a heat sink. When it died it was blowing F4 so i replaced it and the amp would work for 30 minutes or so then nothing. However the fuse was still good, so i took the board out and did some investigating for bad solder joints. I found several and touched them up and tried again. The same thing happened, it worked for about 30 minutes and then nothing. I checked voltages, touched up solders again and fired it up. I got all the tubes back but had very faint sound and the tubes were very hot almost instantly. The tube furthest from the power transformer started to red plate and smoke started coming from around the transformer area. Im almost ready to give up, can someone please help.