[Premium-Rx] FW: RA1792 Options

[George Georgevits]

Just a BIG thank you for everyone who has sent me info. on this. I am a
little snowed under with work at the moment, but should be able to start
work on repairs sometime next week. I will keep you posted.

Cheers,
George G


-----Original Message-----
From: Dan Rae [mailto:danrae at verizon.net]
Sent: Monday, 17 October 2011 1:20 AM
To: George Georgevits
Subject: Re: [Premium-Rx] RA1792 Options


On 10/15/2011 8:39 PM, George Georgevits wrote:
> Hi Dan,
>
> Many thanks!
>
> OK so if I read this code correctly, I have the normal 6 filter set (as
you
> have stated), and I have verified that these are indeed fitted.
>
> I should have the S2 frequency standard (S2 = 9442 ST80764), and I have
> found this in there, made by Racal Dana.
>
> I should also have the Integral sideband board and converter kit, the
SCORE
> interface kit, a 1Hz steps with list search, and an AC power supply. I
have
> the AC power supply.
>
> There is also an A1 RF AMP/LPF, and a box labelled 51-3002 on the side and
> 51-3001 by hand on the top.
You should have the ISB board fitted and also the twin 100 kHz convertor
unit 51-3002, which is in the steel box next to the OCXO.  If you only
have the single convertor 51-3001 you only have the one 1oo kHz output,
You can tell by looking.

You say later that you have the GPIB card, so you don't have SCORE.
Only one or the other and the eprom firmware needs to be different.
>
> Along the side, it has what I assume to be the processor card because it
has
> three ROM chips and a battery on it. The battery reads 2.8V so appears OK.
> The handwriting on the ROM chips has faded, but I think one says 83056/2/A
> Issue 1 8244.
Battery 2.8V when the set is not powered?  A duff battery will still
show a Voltage when the thing is on. If it is a Nicad, you should change
it anyway, if it hasn't leaked already, it will.  Fit the NiMH variety.
See below!

83056 firmware is for the gpib interface so that tallies with what you
have, not the plate.  1 Hz steps, I think scanning in 10 channel groups
and special facility, which I think was a spook thing to clear all the
memories by pressing the four corner keys on the keypad, so the office
cleaning staff couldn't tell what you had been listening to.
>
> > From the underside, I see an A2 1st Mixer, an A7 1st LO, a 2nd Mixer and
an
> A8 2nd LO.
>
> On the rear, it states DRG No. ST 80730, which I presume means I have the
> "A" version.
They are all As.  You could have the Mark 1 to 3 and can tell by looking
at individual boards...
>
> On the rear, it appears to be fitted with J2 main IF output (presumably
for
> the 100KHz ISB option, a J7 LO output and a J1 REF IN/OUT.
>
> Most importantly, it has the GPIB interface. I have quite a good
collection
> of HP ISA GPIB cards and have written a lot of software to drive vector
> network analysers and other HP test equipment from a PC. I was hoping to
> write something to control this RX.
>
> Cosmetically, it looks quite good.
>
> I tried firing it up - dead as a doornail. Checked the fuse - OK. So I
guess
> the power supply is first on the list.
>
>
First on the list would be to find the dead tantalum or tantalums that
are pulling the supplies down.  When the power rails are all present
then start with the cpu board which is where 90% of faults happen due to
the battery alkali leakage.  They are all fixable but can need a lot of
work...  On my first '92 I had 4 dead tantalums, so decided to change
them all.  Never again, it's a LOT of work.  I just do the ones that
fail now when needed.

I have fixed many A6A2 cards; the alkali gets under the solder resist
and into the VIAs, even if there is no visible damage there can be many
open connections.  It wicks up transistor wires, eating them through and
into the 34 way connector, and worse still into the IC sockets, many of
which I have had to replace.  Look for green or blue corrosion.

At least the manual scan that is around is the right one for the older
'92s so you are good there, but it is not that easy to read in places.

Good luck,

Dan