Hi. First post after lurking here for a while. I've been reading some of the recent posts about power transformer temperature and it's got me wondering just how hot is too hot. I have a new st70 with KT-88's that I built from the kit a few months ago. After extended use in a warm room the power transformer gets pretty hot. Not burning hot or anything. Just uncomfortably hot where you can't hold your finger on it for longer than a few seconds. Is this normal? I've put about 250 hours on the amp with no ill effects. Basically I'm just wondering if this thing is like a neon sign transformer and it's designed to run hot in normal operation.
Btw it's only the power transformer that gets significantly hot. The two output transformers just get slightly warm to the touch.
The tube setup and bias is the following
4 sovtek KT88's biased at around .510-.520 each (it won't go any lower)
The original ruby 5ar4 arced over internally after like 5 hours of use and kept blowing the fuse after that( them darn chinese). Since then it's been using an old copper plate GE 5ar4 without any issues.