[Amps] switchable zener cathode bias

[Mel]

Steve,
 
I placed the two zener diodes in series and used a set of relay contacts to bypass one of the diodes to lower the zener voltage and make the tube run hotter (or cooler).
 
73
 
ko0m

--- On Tue, 12/30/08, Steve Flood <kk7uv at bresnan.net> wrote:

From: Steve Flood <kk7uv at bresnan.net>
Subject: [Amps] switchable zener cathode bias
To: amps at contesting.com, rfamplifiers at yahoogroups.com
Date: Tuesday, December 30, 2008, 11:53 AM

Considering the common zener bias circuit (with the 2n3055 and resistor), what
precautions should be taken if I wanted two different zeners (and associated
bias voltages) selected by a switch or relay?   Is there a danger in the moment
when the switch/relay throw is transferrring from one pole to the other and
neither zener is in the circuit?   Likewise, if I used a make-before-break
setup, can the two zeners be in parallel for a moment without causing trouble?

Thanks,
Steve KK7UV
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