[R-390] EAC AGC

[Guido Santacana]

Hi Larry,

  I already have it at 113VAC with a Variac that I connected today but will
do the bucking transformer project because I use the Variac on other
smaller radios and for this one I want a dedicated power source. The caps
that I used, and have used before, are polypropylene types that seem to
work quite well. Voltage rating is at 630VDC. I sent for a couple of 2uF
caps to replace C551. There were none in my parts box. I can install it
underneath the IF deck and keep the original for the looks.

  Today I performed the old Chuck Rippel procedure for IF gain adjust and
to my surprise I was able to peak the noise with the antenna trimmer at
15.2MHz with no antenna connected, so I was able to lower the noise floor.
The original multisection 30 and 45uF caps are holding well. I tested them
at max voltage days before and apparently they are still ok. They also
tested well in my cap meter and ESR meter. Nonetheless I am keeping them
under surveillance for any leakage or heat. After I get the 2uF C551 in and
also replace C609 then everything will be prepared for alignment. The
vedeer root counter is a bit off but I think that it can be corrected with
the zero adjust. The fact is that I bathed the whole gear section with WD40
to clean out the crud and forgot to take out the WD40 from the zero adjust
area. It is slipping. My bad! as millennials say now. The set has been on
today for 3 hours with excellent sound and good sensitivity. Now I wish
that one R390nonA would suddenly appear around here as this one did. Then
my setup would be complete because I already have the R392. The next
challenge is looking for space in this crowded shack for this set. I may
get rid of some of my sand state stuff.

Best 73s

Guido

Guido Santacana KP4FAR

On Tue, Aug 2, 2016 at 10:26 PM, Larry H <dinlarh at att.net> wrote:

> Hi Guido,  Good plan for the 125v ac in - that high is not good.  112 to
> 117 is a good target.
>
> And, very good on the caps.  I assume that you know the recommended type
> for c553: sbe 225p, 418p, 715p   (715 is larger due to polypropylene) orange
> drops. These are 'film and foil'.  Don't use metalized film.  400v should
> be the minimum, 600v is suggested as they last longer.
>
> Let us know how it turns out.
>
> Regards, Larry
> ------------------------------
> *From:* Guido Santacana <gsantacanav at gmail.com>
> *To:* Larry H <dinlarh at att.net>
> *Cc:* "r-390 at mailman.qth.net" <r-390 at mailman.qth.net>
> *Sent:* Tuesday, August 2, 2016 3:41 PM
> *Subject:* Re: [R-390] EAC AGC
>
>
> Hi Larry,
>
>   Thanks for the information. I replaced all the bumble bees in the IF
> deck and also C553 and 549. Will do the same with C551. My last R390A here
> was gone back in 2000. This one appeared in a hamshack and was stored for
> about 35 years. It required major cleaning, recapping, tube pins cleaning,
> a lot of Deoxit, main chassis cleaning after removal of all decks and
> reassembly. Luckily it came out strong.
>
> I want to build prepare a bucking transformer to run this radio at a line
> voltage that is more in agreement with the times when it was built
> (110-115VAC). The line coltage here is almost 125VAC. The set requires 140
> watts without the crystal ovens so I think that a 3 amp bucking transformer
> can do the job.
>
> Many thanks for the info and 73s
>
>
> Guido
>
> Guido Santacana KP4FAR
>
>
>