On 11/08/2010 15:45, Carl wrote:
----- Original Message -----
From: "David C. Hallam"<dhallam@knology.net>
To:<dezrat1242@yahoo.com>
Cc: "Amps reflector"<amps@contesting.com>
Sent: Wednesday, August 11, 2010 10:03 AM
Subject: Re: [Amps] 50 watt stud mount zener diodes
It's good that NTE can still supply them if needed, but their prices
take you breath away.
David
KW4DH
Just another reason for 1N5408 or 6A10 strings. A tube arc will take out a
50W zener as fast as a 10W version.
Carl
KM1H
Carl, et al -
50W Zener diodes are now "hard to get" items in the UK - they are
expensive, never quite the right voltage, noisy, and drift with temprature.
Have you considered making a "programmable Zener" using a TL431 and a
TIP147 as per Ian G3SEK's "Triode Board" design (circuit attached).
The full Triode Board info can be found here:
http://www.ifwtech.co.uk/g3sek/boards/triode/triode-manual.pdf
the grid bias circuit is on page 11 (and attached) and can be built on
its own. I have substituted one in to a 50MHz 3-500Z amp (the QST 1970
design) and it works great.
This circuit is protected (assuming you have glitch resistors) by the VDRs.
Mike G8TIC
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