[Central-Electronics] My CE 20A once again

[RJ Mattson]

Hi Jim
Tnx for the reply.
I just got another reply that said I should get out the label gun!
I like ur reverse a secondary winding better.

I'm kind of vague on where my rewire info came from.
The W2EWL xfmrs are 22K CT to 600 CT.

Each plate of the AF Mod 12AT7 is shunt fed with 22K 2w resistors to B+
The xfmr primary (22K CT) is in series with a 10 mfd  350v and goes from
plate to ground.

The xfmr sec (150 ohms) is wired normal (I'll reverse one winding).

I'm wondering since non-polarized 10mfd are available cheap now if there is
any advantage to switch ?
I'm also thinking, if this shunt feed was done as a modification, the old
xfmrs would not have opened?

b well,
bob...w2ami x wn2ami 1962

On Tue, Aug 21, 2012 at 3:24 PM, Jim Candela <jcandela at prodigy.net> wrote:

>
> Bob,
>
>    If it works good as is, I'd re-calibrate my brain and just use it. To
> make it right you need to swap the phase on one of those transformers, and
> I'd pick the secondary side.
>
>    Your story is interesting. Those transformers in Tony's W2EWL special
> capacity coupled the audio to the primary of those transformers, and then
> they used a plate load resistor on the driver tube. Is that what you did?
> If so what R, C values did you use?
>
>   Someone else replaced those transformers with a pair of Radio Shack
> 120V/12V 300ma transformers and had good results. These have a 10:1 turns
> ratio (100:1 imp ratio), so they are about right for matching 20K to 200
> ohms.
>
> Jim
> WD5JKO
>
>   ------------------------------
> *From:* RJ Mattson <wn2ami at gmail.com>
> *To:* CE_20A QTH <central-electronics at mailman.qth.net>
> *Sent:* Tuesday, August 21, 2012 9:59 AM
> *Subject:* [Central-Electronics] My CE 20A once again
>
> Back in the 1960's, I bought a used 20A and 458 vfo.
> I used it for many years before it failed to work.
> One of the modulation xfmrs had opened.
> I bought two W2EWL xfmrs and a schematic at a hamfest for the repair.
> The W2EWL bal mod xfmrs were advertised for years in QST to homebrew ssb
> xmtrs.
> The schematic and parts bag sat inside the 20A cabinet for years until this
> August.
>
> I installed the xfmrs and wired them in per the old sketched schematic.
> I also replaced a dozen or so parts out of tolerance.
>
> It works great on ssb from AWA net check-in reports.
>
> The only problem is the SB1 and SB2 are reversed from what the
> manual states the USB or LSB should be for each band tried.
>
> Do I need to reverse a mod xfmr winding  ?
>
> b well,
>
> bob...w2ami x wn2ami 1962
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