On Fri, 04 Feb 2005 05:55:55 GMT, "James Sweet"
wrote:


"NSM" wrote in message news:EPDMd.301$rB6.91@edtnps91...

"Sam Goldwasser" wrote in message
...

Hmmmm. Cost of electricity to run heaters: Totally rough guess of 100 W
over
10 years or about 8,000 kW-h. What did electricity cost back then?

About 3 cents per KWh.

How did the cost of the electricity to keep the heaters lit continuously
compare to the cost of a service call to replace a tube?

I'd have been doing the replacing and the kine ran till the set died. They
didn't all do that, for sure, I replaced my share for other people. That's
how the old tube computers kept going too, keep the filaments alive.


Doesn't keeping the filaments heated boil off emissive material from the
cathode? I haven't had a ton of vacuum tube equipment but of 2 dozen or so
bad tubes I've replaced, only *one* of them had an open filament.


Most tube sets I came across had their standby reduce the current
going through the filaments.