Hi Bill, if by "floating the screens" you mean no voltage applied and no
path to the cathode, then this is not a good thing! The screen voltage will
very
quickly rise to the plate potential and with no grid bias, the plate current
will jump to a very high value. The result will be a very sudden and loud
"KAPOW". To prevent this a current path between the screen and cathode has to
be present. I have not used this tube so not sure what the resistance value
should be but probably several K ohms.
73,
Gerald K5GW
In a message dated 3/14/2005 3:09:52 P.M. Central Standard Time,
n2bc@stny.rr.com writes:
Adding a "tune" mode to an AM RF PA with a pair of 4-400s. What's
better... floating the screens or grounding the screens. Does it matter?
To round out the picture: no bias supply (grid leak bias only), screen E
derived via dropping R from plate B+
I have a relay that will easily handle the screen voltage and plan to switch
in a suitable R in place of the screens to keep the voltage coming into the
RF deck near normal screen value. I don't foresee it ever being 'hot
switched' - It probably wouldn't last too many cycles at 3KV. I don't want
to mess with a clamp tube.
THX & 73, Bill N2BC
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|