Bill,
I make the basic assumption that the Zener in your case is to set the
Zero-signal Anode current (PTT and no signal) to the correct value. and
that value you will find in the manual and the tube-data.
Instead of a Zener, do as suggested before: Buy 9 pcs of 1N5408 and put
them in series, each diode will have about a 0.7V drop, independent of the
Bias-current through it. So with 9 diodes you will have 6.3V. Please note
that with this method you have to turn the diodes so the current passes
through them.
The "Zener-Voltage" is not important, what is important is the Zero-signal
Anode current, now you can adjust that current by selecting the proper
number of diodes!
73,
Thomas Carlsson, PY2ZXU, SM0CXU
On Thu, Feb 12, 2015 at 9:40 PM, Bill Turini <mailing_lists@hamanuals.com>
wrote:
> Folks:
>
> On 2/2/2015 2:36 PM, Bill Turini wrote:
>
>> I need a zener for my 2KD-3. It's a 1N4561. It appears that they are
>> really hard to find and exorbitantly expensive when you do. Has anyone
>> found a source for a replacement at a reasonable cost?
>>
>> This request generated many wonderful replies and suggestions to fix my
> problem. Last night I was RTFM when I noticed something very strange - the
> zener diode I had removed from the amp was not the same as identified in
> the schematic, and it was connected totally differently from the
> schematic. Remembering the wise post from the Henry web site, I decided
> not to trust my eyes or the schematic and asked the learned group for their
> opinion.
>
> First, the zener diode I removed from the amp was a 1N4561, a 5.6v 50 watt
> device. The schematic calls for a 1N2804, a 6.8v 50 watt device. Since
> the removed device was not wired in any way close to the schematic, I
> assume that this was an attempt at a repair or "improvement". So, what
> should the voltage be? 5.6 or 6.8volts? Or should it be something else?
> Since most of the other Henry 3-500z amps have 10 volt zeners, I would
> vote for the higher voltage 6.8v device.
>
> Second, as for the wiring in the amp, I think it is just wrong, since all
> the other Henry GG amps have the cutoff circuitry the same. So, I'm going
> with the schematic.
>
> And, in case anyone is wondering, the 1N2804 costs just about the same
> ridiculous price as the 1N4561, so I'll probably opt for the zener and
> transistor route.
>
> 73's and thanks in advance.
>
> Bill
>
> --
> Bill Turini
> KA4GAV
>
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>
--
Thomas, PY2ZXU/SM0CXU
Member of the PW2D Team
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