[Ian Thompson-Bell]

I have just built a test rig to check a hunch of 6N1P double triodes.
Nothing special, just an 820R cathode resistor, 47K plate resistor, 300V
supply and the grid grounded - two sockets tests four triode sections at
once.

Each time I changed tubes I noticed how hot they felt so I stuck a
thermocouple on them and found they reached 84 degrees C (ambient is 23
C at present).

The I put in a pair of PCC88s and they reached only 50 degrees C. Now
this was not totally unexpected as the 6N1Ps draw twice the heater
current. I think the plate dissipation was about the same in both cases
although they ended up at different operating point.

Is this 84 degrees an OK temperature for a preamp tube??

Cheers

Ian