[Amps] Alpha vs Henry - tube temperature

[John Lyles]

I use the old fashioned but accepted method to measure tube 
temperatures, a range of Tempilaq paint or Omega's labeled versions of 
the same, Omegalaq. It takes some practice to get a dot of paint without 
making a glob. Try it on a piece of metal in your oven first. Place it 
on locations of the tube that are air cooled, or not. Such as around the 
filament connector rings, the screen ring, the ceramic seal under the 
anode (use a very small dot here). It should work on glass tubes as 
well, just keep the amount small. It is not a cheap method, though, as 
you need a range of temperatures to get any resolution. I tend to use 
100, 115, 125, 139, 150 deg C or something like that. Then run the tube 
at full power, shut down and read the results. Rarely do I like to 
exceed 150 deg C in commercial amplifier designs, as the thing may have 
to work at higher elevations or with dirty air filters at some point.

73
John
K5PRO