[Amps] Re: Amps Digest, Vol 21, Issue 44

["David Lisney" <g0fvt@lisney.org.uk>]

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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