>
>Radio WC6W wrote:
>
>> The shunt regulator consists of a venerable uA723 regulator IC driving
>>a FET. The FET is connected to the screen through a series R which drops
>>most of the voltage and therefore dissipates most of the heat. The '723
>>is powered from a +15V supply which is independent of the plate supply.
>> ...
> ...
>However, it does show that the more you think about screen supplies, the
>more potential failure modes you see, and the more complex the design
>becomes to defend against them. Marv's is complex; Acom's is complex;
>Alpha's is complex; and G4JZQ's and mine is complex. We all did it
>differently, but we all agree that a handful of cheap zeners won't cut
>it.
>
- The only person who used cheapie zeners is the one who sells
sophisticated screen regulator boards. I used quality zeners at about
35% of the max diss rating (at 25ºC case temperature) because I realized
that the case temperature would be somewhat higher -- especially when I
was operating AG6K/HE1L atop Mt. Purgatory in the ARRL June VHF contest.
cheers
- R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K,
www.vcnet.com/measures.
end
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