>Series pass stabilisers do not absorb the negative screen current that
>tetrodes typically generate. Using a series pass stabiliser causes the
>screen voltage to go up and down in sympathy with the negative and
>positive screen current, which can cause the tube to flash-over with
>spectacular results!
Not if one uses the recommended amount of screen bleeder current. [see
Figure 5 on my Web site]. For tetrodes with handles, which typically use
1.5kV screen potentials, shunt regulators are neither practical nor
energy efficient.
>
>The only safe screen stabiliser is a shunt stabiliser. This can be made
>using either mosfet's or bipolar's, the tv industry has some good (cheap)
>devices which can safely handle 1500V. Today the tube shunt stabiliser is
>a bit of an oddity, but they can still be made to work, but transistors
>are a better choice.
>
>John ZS5JF
>-----Original Message-----
> From: Rich Measures <measures@vc.net>
> To: Bill Coleman <n2bc@ibm.net>; amps@contesting.com
><amps@contesting.com>
To: <amps@contesting.com>
> Date: Sunday, November 15, 1998 3:34 PM
> Subject: Re: [AMPS] Screen regulator circuit needed
>
>
>
> >
> >I'm wrestling with trying to get a couple of 811s and a string of VR
tubes
> >working as a regulator on a 1KV screen supply for a 4-1000 in AB1 (early
60s
> >handbook circuit).
>
> ? One needs triodes with a Mu of under 5 for pass regulator service .
>
> >I picked this circuit because I had the 811s. So far I've
> >succeeded in building a nifty 200W or so LF oscillator (big surprise)
--
FAQ on WWW: http://www.contesting.com/ampfaq.html
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
Search: http://www.contesting.com/km9p/search.htm
|