[Amps] Re: Amps Digest, Vol 21, Issue 44
David Lisney
g0fvt at lisney.org.uk
Sat Sep 18 02:30:14 EDT 2004
My little tetrode amp has two mains transformers, one for heater, grid bias
and screen volts, the other for HT and the various relay supplies. So the
second transformer is not powered until warm up period has passed.
I personally do not believe that it matters to have screen voltage present
without HT as long as cut-off bias is applied to the grid and hence no
screen current flows.
My screen supply is regulated, but has current limit to limit screen
dissipation to a safe level in the event of HT loss while transmitting, also
it will crowbar down to 0v in the event of excessive negative screen
current.
I could very easily key the screen voltage so that in RX mode the screen is
down to chassis, it would cost me a few inches of wire, but I ask myself
why?
I appreciate the Eimac know their products literally inside out, however I
am sure that the "care and feeding" does not consider every possible circuit
configuration. I do not see any obvious abuse I am putting my tube through
by operating it as I do.
73 de David G0FVT
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