.
> Eimac does not say anything about limiting the startup current to the
> 8877 heater. While it is true that directly-heated cathode tubes have
> about 8.3-times less filament R at startup, the heater of indirectly
> heated cathodes does not exhibit a large R decrease when cold.
>
> cheers
>
The question was about a 3CX1200A7, I thought.
Measurements have shown that inrush on the heater of this series tube
can exceed the limit, especially if the filament transformer is more robust
than the required current rating of the heater(s) it is powering.
Also, the guys turn their amps on and off thousands of times more in the
life of the tube to get rid of blower noise/save energy, etc. than folks who
run 8877 amps. That increases the chance of inrush by many times that
of tubes that require 3 minutes before keying up. I just think it is good
financial sense to spring for the $2 for a $600+ insurance policy.
99% of all light bulb failures occur the instant the switch is turned on.......
Surely, this economical feature would be included in the parts list for the
"Nearly Perfect Amplifier" don't you think, Rich?
(((73)))
Phil, K5PC
--
FAQ on WWW: http://www.contesting.com/ampsfaq.html
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
Search: http://www.contesting.com/km9p/search.htm
|