Even Steven wrote:
I'm working on a Hallicrafters SX-25 Super Defiant. It uses two 6F6
tubes in push pull in the audio
circuit. Boy do they get hot! Too hot to touch. If my finger lingers I'd
have an awful blister in less than a second. Is this normal? I've checked
the tube voltages and they seem to be where they should be...280 VDC on
plate, 6 volts on heater, 18 volts on cathode. Does anyone have any ideas
about how to help these things run cooler?

If the quiescent cathode voltage is good, you can rule out a bias problem
although it might be worth replacing the coupling cap pre-emptively. The
heat tends to bake 'em.

About all you can do is remove the 6F6 and put in a tube with a higher
dissipation rating.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."