The B52 amp I have runs pretty hot. Not so hot that I can't touch it but hot enough that it feels warmer than normal. I installed a cooling fan and that helps but the front panel(mostly next to the power switch) gets fairly warm.
It's the AT-100 and I've read that it may be biased to hot and that might cause some of the heat problems. Is that true?
If it was biased hot it'd be pulling more DC current through each of the tubes. This'd come through the power supply and more current equals more resistive losses which generates heat. I don't know whether a hot bias would be entirely responsible, but I'd imagine it would certainly contribute, especially around the input connector and rectification components.
There could be poor ventilation around these components also, heatsinks may be blocked with dust etc. If something is faulty it could be operating at a lower resistance, causing higher current flow - that's fairly unlikely though. Which components in particular are heating up? Or is it just the front panel in general?