[Amps] The GU84B and GU78B tubes / some brief history

[Ian White GM3SEK]

Vic K2VCO wrote:
>I'm thinking about this issue now for my project 4CX1000A amplifier. 
>The problem I see is the first element getting chopped by the screen 
>relay pull-in time, which would have to be under 8 ms. to work.  I am 
>going to use a fast bias switching arrangement along with the QSK RF 
>relays as usual, but it would be nice to also switch the screen voltage.
>Presently, I'm planning to have an "amp enable" switch which will turn 
>on the screen voltage and connect the transceiver key out to the QSK 
>relays. So the amp won't necessarily be 'armed' whenever it is warmed 
>up and ready.
>I have an extra vacuum relay that I could use for this, but Ian's board 
>seems to be designed for a 12v relay in this spot!

If you already have a +24V rail available, it will be easy enough to 
interlock the vacuum relay switching with the 12_HV rail on the board. 
Looks like three logic-level MOSFETs will do it... I'll PM you a small 
schematic later.


-- 

73 from Ian GM3SEK
http://www.ifwtech.co.uk/g3sek