Wait at least 30 seconds. The 813 doesn't have instant heating filaments
like the 3-500z.

73

Ralph VE3BBM
"Rick" wrote in message
...
How long after applying filament voltage till the 813 is ready to
transmit? Is it like a 3-500 or do I have to wait 30 seconds or so?

Rick K2XT

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

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