External heating?

[Don Symes]

Thought I saw a question on this idea go by, but couldn't find it.

Once upon a time, I worked for a company that designed instruments to measure the characteristics of wellbores, where temperatures routinely reach 200C. There were some museum-piece instruments around and one of the old hands was pointing out the tubes, reminiscing that because the temps were so high, they didn't need to worry about heater current - they just used the ambient heat.

Was my leg being tugged?

What temperature range(s) do our favorite tubes favor?

Would my tubes last longer - or at least as long - being run in an oven than with their internal heaters?

/ my feature creep tendencies are creeping back

[Enzo]

Well it sure sounds like a left handed monkey wrench, but you never know. I can't imagine inside that vacuum bottle that there would be consistent cathode temperature. Is 200C enough to make metal incandesce? If the whole tube were that hot wouldn't it increase noise? Of everything in there is hot enough to create a space charge, how would that affect operation of the tube?

According to the RCA book, page 4 in mine (RC28), indirect heated cathodes are held by the heater at 1050K, so what is that in Centigrade, maybe 750C? I don't think 200C comes very close.

Look for finger marks on your leg.

[Don Symes]

According to the RCA book, page 4 in mine (RC28), indirect heated cathodes are held by the heater at 1050K, so what is that in Centigrade, maybe 750C? I don't think 200C comes very close.

Look for finger marks on your leg.

Hmm. A google on Kelvin to Celsius yields 1 kelvin = -272.15 degrees Celsius.
That would say 200C is 447.15K and 1050K would be about, yeah 750C.
And, for my avoirdupois-addled mind, 1050K is roughly 1430F.

A hydraulic-assisted left-handed monkey wrench with a sable-leather grip and digital torque readout.

[Enzo]

MAke sure it is metric too.