On 28 Jan 02, at 14:21, Steve Thompson wrote:
> Possibly or probably - I'll find out when I fire one up (anyone out
> there save me the bother?). They put -ve contours on the 4CX1600B so
> maybe they just cut and pasted the text. Happens all the time - or did
> when I worked in the semiconductor business. Anyhow, that's a
> digression. My guess is that any -ve current is likely to be small,
> and normal operation appears to run around 40mA +ve. It seemed to me
> to be wasteful dumping 40odd mA all the time in a shunt just to meet
> peak demand so I designed a series circuit, then got to thinking about
> protection which is where I came in.
When I was doing my 4cx800a/Dentron MLA2500 conversion, I got some
plate curves from Svetlana in Russia. I decided that -20ma was the
most "wrong way" screen current I'd ever get for a single '800a... I
diesigned my screen regulator with a zero signal 20ma drain (see "New
life... QST, May 1996, if you want.) In actual pretty heavy use
(contesting) with varying antenna loads and driving conditions, I
never noticed any more than about -5ma; when it's driven properly and
loaded properly, +15 - 20 ma is what I see. (All numbers are "DC"
meter readings. It's not that the tube doesn't EVER swing into
negative screen current on RF anode current peaks... I don't monitor
that.)
73,
George Daughters, K6GT
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