Hi Dom
1kV on the screen i nothing to worry about if you have ~5kV on the plate.
I´ve been running my 2m QBL5-3500 amplifier like that the last 10 years
(with the same tube). I also have the screen supply unregulated with just
a big bleeder across the supply terminals.
But..... a good screen regulator is better if you run SSB.
Take a look at the AG6K web site: http://www.somis.org/D-a-08.GIF
Screen supply: 2kV maximum - 0,1% regulation
Good enough I think.
73 // Einar // SM3MXR
DEHAYS Dominique skrev:
> Hello ,
>
> I'm looking for ideas.... I am using a QBL5-3500 amplifier on 2m. Untill
> now , I have been using unregulated screen power supply with quite good
> success , but since I've moved to a new place , my mains voltage is higher
> than previously and my screen voltage went up to 1000v ( instead of 800v
> recommanded for that tube) . Off course , it is possible to use a small
> variac on the transformer primary , but a better idea would be to design
> and build a 800V screen regulator , if possible , an high performance
> design , like the one designed by GM3SEK in his famous " Tetrode Boards" ,
> with the various protections needed..
> But the tube is a little bit greedy ( or GRIDdy :0))
>
> Screen voltage is 800V WG2 power is 100W maximum , so screen current can
> go up to 120ma during normal operation. There is nothing said in the tube
> data sheet about negative screen current , but there is no reason why it
> cannot occur.
> So I am looking for a design able to statisfy my needs. Maybe the GM3SEK
> can be modified to run with that tube?
>
> 73 Dom/F6DRO
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