[AMRadio] Johnson trannies...

Sat Jun 4 14:37:19 EDT 2011

IMD deteriorates with the 3-500 when the Ep starts getting up over 3
KV (according to what I have read).

I've seen a table with 3rd order spec's for different Ep from 1.5 KV
up to the limit, of course I can't remember the source for the data
which is why I try to avoid technical disputes--I can remember general
facts but can never say where I got them--but I remember at around 2
KV the tube looked pretty darn good with the 3rd order down around 40
dB or more, at 3 KV it was okay but at 3.3 or higher it began to get
less than 30 dB down from fundamental and be marginally legal.   I
have no idea how the measurements were made so don't take it as
gospel.

I still think it is a great tube, 20 w. grid dissipation for one
thing--a ham has to almost have to be deliberately trying to damage
one to damage it (or not know what he is doing).  I went through a
period where I contemplated the ceramic tube route, but decided to
stick with glass.

73

Rob
K5UJ

On Sat, Jun 4, 2011 at 10:19 AM, Kim Elmore <cw_de_n5op at sbcglobal.net> wrote:
> I noticed the same thing with a transformer that Dahl designed for me
> many years ago. It's a replacement for the original AL-80A
> transformer designed to generate about 3.6 kV B+ under load using a
> FWB instead of a doubler. This was the result of a question that went
> like "I wonder how much I'd get if I ran the 3-500Z right up against
> its voltage rating limit?" I had to alter the output network values
> because this changed the output impedance (something I had not
> considered until I tried tuning up the amp) but with the appropriate
> changes it's well-behaved. All the effort bought me a bit over 1 dB,
> and so wasn't worth it from the standpoint of increased output, but
> the knowledge gained was far beyond price.
>
> Kim N5OP
>
> At 08:04 AM 6/4/2011, you wrote:
>>yeah but the big question is do they still sell it and for how much.
>>
>>The Dahl drop in replacement for the B+ transformer in the Ten Tec
>>Centurion amp mysteriously disappeared from their list a few years
>>ago; I have no idea why but I'm sure glad I got mine before that
>>happened.  It is far and away better than the stock transformer.
>>
>>73
>>
>>Rob
>>K5UJ
>>
>>On Fri, Jun 3, 2011 at 10:41 AM, Kim Elmore <cw_de_n5op at sbcglobal.net> wrote:
>> > Hi Jim,
>> >
>> > I do believe that you pulled that right off of the Peter Dahl/Harback
>> > web site :) It's pretty handy for stuff like that. It's amazing how
>> > many different transformers they've re-engineered for the old rigs!
>> >
>> > 73,
>> >
>> > Kim N5OP
>> >
>> > At 09:11 PM 6/2/2011, you wrote:
>> >>I think this is what you are seeking:
>> >>
>> >>JOHNSON VALIANT DRIVER XFMR
>> >>P/N 22.1286, T4
>> >>CORE) EI-062 X .75           STYLE #) 01  E-I LAMINATED CORE
>> >>PR) 230 OHMS DC (12AU7 AUDIO DRIVER PLATE)
>> >>
>> >>S1) 800 OHMS CT (PP 6146 MODULATOR GRIDS)
>> >>
>> >>DM) HT =  1.643 WT =  1.955 DT =  1.438 MD =  0.000 MW =  2.375
>> >>
>> >>
>> >>
>> >>----- Original Message -----
>> >>
>> >>
>> >>
>> >> > Thanks, Darrell. Do you, or anyone else on the list, happen to know
>> >> > the
>> >> > specifications of the driver transformer in the Valiant?
>> >> >
>> >> > -----Original Message-----
>> >>
>> >> >
>> >> > Not the same transformer. The Ranger uses an interstage transformer
>> >> > (step-up). The Valiant uses a driver transformer (step-down).
>> >> >
>> >> > Darrell, WA5VGO
>> >>
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