[time-nuts] Repair of Racal switches

[Andrea Baldoni]

On Wed, Feb 22, 2012 at 08:23:34AM -0500, James Robbins wrote:

> Hello Andrea,
> Thanks for your insight into repairing Racal 1992 switches.  Could I
> ask for more detail about which "6x6mm tactile PCB switches" you
> actually used?  Also, any more detail about what part of the switch
> needed "tape"?  Many thanks.

Unfortunately I cannot give you exact part code of the switch used, because
I bought them from a local store and they didn't know. I just looked on
digi-key and the FSM2JH looks really very similar. Anyway, most of them
should work ok, if you choose a type with very short actuator.

The procedure is as following:

1) open the original switch (if you can, try to not break the minuscule plastic
retainers that lock the moving part in place... if you break them like I did,
you will need to use something to keep the thing from opening itself after the
repairing - I used the roof of the new switch and tape for this)

2) clean the inside

3) open the new switch by cutting the four plastic round retainers in the
corners and lift the roof - you need to keep all three pieces: the lenticular
spring, the actuator and also the flat sheet plastic (or metal) roof (this one
will be useful only if you break the plastic lock on the original switch)

4) put rectangular tape over the golden contacts on the original switch
Dimensions are exactly 5.5x2 mm. I gone to a printing
shop who cut adhesives and asked them to precut (half-cut) a piece of it.

5) put the lenticular spring over it, fix it with another identical tape
6) put the new actuator over it
7) put the old actuator over it - if the new switch is of the right type
they will match together, otherwise maybe glue or filing may be needed

8) the switch is now closed and should work correctly, but if you broke the
retainers on step 1, it will open easily. To avoid this, I put the roof of the
new switch over the old and tape it to the borders. I asked the printing shop
to cut a cross with a hole in it for the purpose, but normal tape could be
good anyway.

I have some helpful pictures put they are too big for the list. If someone
is interested, just ask.

Best regards,
Andrea Baldoni

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