-----Original Message-----
From: rich <2@mail.vcnet.com>
To: Steve Thompson <g8gsq@qsl.net>; AMPS <amps@contesting.com>
To: <amps@contesting.com>
Date: 29 January 2002 22:03
Subject: Re: [AMPS] Shunt regulated high voltage psu
snip
>>>There doesn't seem to be any real need for an active series element to
>>>feed an active MOSFET shunt regulator. The loop gain in the shunt part
>>>is already very high, so the series feed can be just a plain resistor.
>>
>>Certainly, in that configuration. There's numerous valves where the
reverse
>>screen current appears to low or non-existent (4CX800 for example), where
>>dumping 40+mA all the time in a shunt regulator feels wasteful.
>
>// Low screen-V tubes such as the 4cx800 (350V-sc.) suffer more from
>reverse screen current than tetrodes with handles. However, even
>4cx5000As and 4cx10,000s occasionally exhibit reverse screen current with
>1200 - 1500 V on the screen. Bleeding 25mA seems to take care of the
>problem.
>
>>This led me
>>to look at series supplies, which led in turn to thoughts about effects
>>under fault conditions.
>>>
>// Did you look at the screen current curves for the 4cx800?
Certainly did. The Svetlana data sheet shows no areas of negative screen
current, even though the text discusses the need to cater for it.
Steve
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