[Amps] 3.5 kV 2A REGULATED Power Supply: Schematic ?

[peter.chadwick at Zarlink.Com]

Rich said:

>Stabilizing the screen supply with a series pass regulator is not
>good engineering practice unless a screen supply bleeder is used to
>protect against reverse screen current.

I didn't make it clear that the  'low impedance' screen supply means low
impedance both for source and sink - i.e good regulation for both source
and sink..  For 6146B's, I use zeners - not ideal, but the screen current
doesn't go very negative - rarely more than 1 or 2mA.

>Stabilizing the grid supply in AB1 is of little value since there is
>neither forward or reverse grid current.

Stabilising has a lot of value if the screen supply is stabilised.
Regulation is the parameter that has little value. Stabilising both is best
to get around mains variations.

Definitions:
'Regulation' is a measure of the variation of output voltage with load.
'Stabilisation' is a measure of the variation of output voltage with input
(mains) variation.


73

Peter G3RZP






                                                                                                                              
                      "R. Measures"                                                                                           
                      <r at somis.org>            To:       "Peter C," <peter.chadwick at Zarlink.Com>, "Ian White, G3SEK"          
                                                <g3sek at ifwtech.co.uk>                                                         
                      05-Jan-2004 01:31        cc:       " AMPS" <amps at contesting.com>, <amps-bounces at contesting.com>         
                                               Subject:  Re: [Amps] 3.5 kV 2A REGULATED Power Supply: Schematic ?             
                                                                                                                              




**  Stabilizing the screen supply with a series pass regulator is not
good engineering practice unless a screen supply bleeder is used to
protect against reverse screen current.   Stabilizing the grid supply in
AB1 is of little value since there is neither forward or reverse grid
current.

>I have found problems when using high impedance supplies with 6146s,
>especially  as they get older.  Especially bad is the Yaesu 'anti flash
>over diode' in series with the screen grid - any negative screen current
>pushes up the screen volts, and the anode current runs away, with
>disastrous results for the valves.
>
>Grid bias and screen  supplies should either both be stabilised, or
>neither. If neither supply is stabilised, variations in supply volts tend
>to cancel. I prefer to stabilise them both, and keep the supply impedance
>(at low frequencies, including zero frequency) low. I'm still using the
>original 6146Bs in my FT102, and after 20 years of hard work, they're
still
>fine.
>
>73
>
>Peter G3RZP
>
>
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