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[AMPS] Screen stabilization in 30S-1?

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Subject: [AMPS] Screen stabilization in 30S-1?
From: (Ian White, G3SEK)
Date: Sat, 27 Feb 1999 14:16:13 +0000

Someone e-mailed to ask how to stabilize the screen voltage in the
Collins 30S-1. 

The 30S-1 uses a 4CX1000 with a DC-grounded screen, and it derives its
total anode-cathode voltage from a positive anode-screen supply and a
negative screen-cathode supply, the two supplies being stacked in

That means the so-called "screen" supply has to provide several hundred
mA of cathode current as well as the few tens of mA for the screen. It's
way beyond the current capabilities of normal screen stabilizers such as
zeners, AG6K's series regulator or my Tetrode Boards, all of which are
only good for a few tens of mA. 

It would be possible to stabilize the screen-cathode voltage by radical
re-wiring - essentially by leaving the existing two stacked supplies to
float, and providing the screen voltage separately - but has anyone
found a simpler idea that will work with the 30S-1?

73 from Ian G3SEK          Editor, 'The VHF/UHF DX Book'
                          'In Practice' columnist for RadCom (RSGB)

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