[time-nuts] Racal-Dana 1992 switches

[Charles S. Osborne]

Matt,

Not seeing a better alternative posted for the Racal 1992, and having dozens
of similar bad Toko switches on some Pacific Measurements 1038-N10 Scalar
Analyzers, I decided to buy a bunch of the Jameco ones and give it a try.

Definitely not a form fit replacement. But if you're not too asthetically
picky they do fit. The leads can be manually flattened with a pair of needle
nose pliers and reformed to fit under and down to match the closer hole
spacing. Also clip off the small plastic alignment pins to allow the
switches to sit flush on the board. The process only takes a couple of
seconds per switch. A lot quicker than removal of the original switches.

The real catch is the hole size in the 1992 original switch layout is a
couple of sizes smaller on one pin than the other. Using a #54 drill bit (no
bigger) you can clean the hole out and enlarge it without taking the plated
thru barrel out of the holes on that one side.

All my switches are in and working. I didn't even put the keycaps back on as
all the manual lead forming didn't necessarily center within the original
panel cutouts and the plastic posts are adequate for use as switches. The
numerical keys in center keypad may require Dan's epoxy trick. Haven't
gotten to that yet.

Now the real question is... is there a clever way to make the Racal 1992
readout the difference in µHz between two GPS disciplined oscillators? My
only other counter, an HP5384A, is offscale at 10.000 000.000 MHz . I'm
referencing the counter with one Lucent RFTG-m-XO and clocking a Lucent
RFTGm-II-XO. Things are working well enough to be beyond my counter's
ability to see any jitter. The Racal says nanosecond time interval counter,
so I bet there's a way to subtract and increase the resolution similar to an
HP53131?

tnx,
Charles
K4CSO
Duluth, GA
----- Original Message ----- 
From: "Matt Ettus" <boyscout at gmail.com>
To: <danrae at verizon.net>; "Discussion of precise time and frequency
measurement" <time-nuts at febo.com>
Sent: Monday, March 24, 2008 1:46 PM
Subject: Re: [time-nuts] Racal-Dana 1992 switches


> On Mon, Mar 10, 2008 at 8:47 AM, Dan Rae <danrae at verizon.net> wrote:
> > David McGaw wrote:
> >
> >  >Does anyone know of a source of push-button switches for the
> >  >Racal-Dana 1992?  I have one that over half are bad.  No luck from
> >  >Racal-Dana or their service house.
> >  >
> >  >
> >  The original makers of that switch (Omron?) stopped making them years
> >  ago.  I wonder why?
> >
> >  The last time I did this I found a switch at Jameco that was a near
> >  exact replacement.  The only difference was that the button was a
little
> >  too loose a fit and needed a dab of epoxy inside to hold it firmly in
> >  place.  These have been working in mine now for at least five years.
> >  The type I used was KIE22 (29 cents each in 100s), however the ones I
> >  got then with  a cross section shape blue plunger do not look exactly
> >  the same as the ones pictured in the current on line catalog.  Some
> >  further research is indicated obviously...
> >
> >  Once they start to go they will all need to be replaced, I'm afraid.
> >
>
> I bought the ones in the catalog, but they don't fit.  The footprint
> is bigger, for one thing.
>
> Matt
>
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