[Milsurplus] [RCA] SRR-13 Article, more

Tue Aug 2 14:34:27 EDT 2016

KenI too initially though that the ac input filter was at fault but looking at the schematic wiring, the filter is connected to the rear apron power connector, then goes to the fuses on the power supply module then to the power switch on the front panel and then finally back to the power supply power transformer.  So, the ac filter is always connected to the ac line but the problem only becomes apparent when the power switch is turned ON.  Perhaps my bench test connector is wired so that the leakage terminal is connected to the low side of the ac line but the proper power connector wiring reverses that wiring.  Will try a spare power supply module and see if the problem goes away.
I will take you up on the offer of a set of mounting brackets.  The two I have made used heavy sheet aluminum which seems to be working just fine but I have had to make several adjustments in hole size to make it fit well!  So much for eyeballing and trying to transfer dimensions!  Using a proper set of mounting brackets as a template is certainly the way to go.
Jim Whartenby205 Charteroak StreetHot Springs, AR 71901-6145
I will be happy to reimburse you for the cost of shipping.
As for the lack of ventilation lovers in the receiver case, I would think that a tight fitting case was in the receiver specifications.  Most likely to prevent signal leakage into the receiver from high powered transmitters operating nearby.  This would also explain the finger stock used around all mating surfaces.  Reading the labels on the ac, audio and IF filters found in the back apron indicates effective filtering up to 400 mc.Jim

      From: Kenneth G. Gordon <kgordon2006 at frontier.com>
 To: antqradio at sbcglobal.net 
Cc: Milsurplus at mailman.qth.net
 Sent: Tuesday, August 2, 2016 12:39 PM
 Subject: Re: [Milsurplus] [RCA] SRR-13 Article, more

On 2 Aug 2016 at 16:58, antqradio at sbcglobal.net wrote:

> Ken
> My test was only for 6 hours with a modified power supply using the FRR-23 as a
> test bed.  With 60 VA ac power input, the temperature reached and stabilized at
> 107 degrees internally and the top of the case was just barely warm.  I can
> imagine that a rack of stacked receivers with unmodified power supplies with
> about 100 VA ac power input would be a bit different.

Well, I am not convinced that that is the only reason. But, as I said, it was a long time ago.

> I have made two sets of brackets so that the FRR-23 and the working SRR-13A
> can be rack mounted.

I have a number of the original rack-mount adapters for these receivers. They are VERY
heavy steel! I can send you a set if you would like to have them. At least you could use them
as models. ;-)

>  This makes working on rhe receivers much easier than
> struggling with a receiver that is table mounted.  One interesting problem that
> popped up with the SRR-13A is that when in the case and rack mounted, it
> started tripping the shop GFCI.  

Hmmmmm....not good....

> Since the GFCI only trips when the SRR-13A power switch is turned ON,
> perhaps there is an issue with leakage in the power supply?

Well, as you know, there are very extensive filters in the back-plane of those receivers. I
would suspect bypass capacitors right at the AC input. This is a common problem with
R-390s for instance.

>  But the receiver
> operates correctly on the bench with a direct connection for ac power to the rear
> connector.  Anyway, using a constant voltage ferroresonant isolation transformer
> cured the problem.  Now I have to investigate why there is a difference between
> the SRR-13A and the  FRR-23 which does not have this particular issue.  Always
> something to look into!

Oh, yes. This is what makes this stuff fun! :-)

>
> I did notice that the back apron of the SRR-13A has one less BNC connector
> then the FRR-23.  This extra BNC connector allows the FRR-23 to have a
> remote First Oscillator.  I guess this is for the diversity setup that allows the LO of
> one of the FRR-23 receivers to be slaved to the other.  While the SRR-13A is
> also capable of diversity reception, each must evidently use independent local
> oscillators.

Yes.

> More to come after I do some housekeeping in the shop!

Boy! Me too!!! :-(

Ken

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