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813 warm up time
The 813 filament is constructed of thoriated tungsten. One of the
characteristics of this type filament is "instant" on. See http://www.w8ji.com/vacuum_tubes_and...e_failures.htm and look under thoriated filament. You do want the filament to heat up and that probably means a second or two. I remember Bill Orr wrote an article about failure of the 3-500 ( which is considered instant on also). Some individual had a number of tubes fail and kept sending them back under warranty. Finally Eimac called him and learned that the chap was turning the tube filaments off between transmissions and turning them on immediately before each transmission. So, do not use either tube for break in cw by keying the filament. 73, Colin K7FM |
#2
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813 warm up time
COLIN LAMB wrote:
Finally Eimac called him and learned that the chap was turning the tube filaments off between transmissions and turning them on immediately before each transmission. So, do not use either tube for break in cw by keying the filament. 73, Colin K7FM I have to wonder what the keying waveform might have looked like. Probably added a unique sound to his signal. Something like a modified banana-boat swing, for lack of a better description? de K3HVG |
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