[time-nuts] Racal-Dana tactile switches

GandalfG8 at aol.com GandalfG8 at aol.com
Sun Apr 22 10:22:49 UTC 2012


I made a successful repair of a Racal 1991 counter that I  originally 
bought as a spares unit, the original switches and switch caps  had already been 
removed and discarded, but decided after all that it was too  good to just 
use for parts, especially as all that ever seems to fail  anyway are the 
switches:-)
 
As I believe others have also suggested I found that 6mm square  tactile 
PCB switches could be modified to fit in place of the original Racal  switches.
 
Refitting the original switch caps wasn't an option for me, but whilst  
trying to devise some convenient method of operating the normally very  squat 
PCB switches through the front panel I came across some  switches on Ebay 
with extended actuators.
Using a switch with an overall height of 13mm allowed the actuator to  
protrude approximately 3mm through the panel and this works remarkably  well.
 
It's obviously not totally ideal, one downside for many would be that  the 
keypad numbering is normally only on the switch caps, although I was  lucky 
with this unit and the numbers were part of the panel markings, but  it did 
restore the 1991 to being a perfectly usable counter.
 
However, given that most users contemplating something similar would  
probably still have the original switch caps, and that it shouldn't be  too 
difficult to refit these to the longer actuators, I think such  switches might 
provide at least one answer to the problem.
 
Anyway, I've written up a few notes to go with some photos I took whilst  
fitting the switches to my unit and have uploaded these to Rapidshare  just 
in case anyone might be interested......
 
 _https://rapidshare.com/files/1424161401/Racal1991Switches.zip_ 
(https://rapidshare.com/files/1424161401/Racal1991Switches.zip) 
 
Please feel free to share or bin this as you think fit:-)
 
Regards
 
Nigel
GM8PZR
 
--------------------------
 
 
In a message dated 21/04/2012 11:22:03 GMT Daylight Time,  
df6jb at ulrich-bangert.de writes:

Gentlemen,

I know I am not the only one in this group to  have difficulties with "weak"
tactile switches on Racal-Dana's 1991/2/6  range of counters. The other day 
I
talked to the chief technician at  Rosenkranz-Elektronik which is one of the
biggest surplus suppliers in  Germany. 

He knew the problem very well and his claim was that an exact  replacement
for the original Toko switches is no more produced anywhere in  the world.
Which may be an explanation why none of us managed to find an  exact
repelacement. 

His second claim was that the switches can be  repared: After removing the
cap gently grip the moving part with  a  pair of pliers and twist it a 
little
bit while pulling it out a bit at the  same time. In this way the moving 
part
can be removed without destruction  of the switch. Then you find the source
of the problem inside: The weak and  mostly destroyed rubber part inside.
Replace it with the rubber part of a  switch which has NEARLY the same
dimensions. He told me that he had done  such a repair for a number of 
times.
Unfortunately he had no reference for  the switches that he had used as the
source for the replacement rubber.  

I am aware that this is only half of the solution of the problem but  I
checked his suggestion with a original switch that I had laying around as  a
replacement and found that his description worked for me. I made a  
photgraph
of the switch to be found here:  

http://www.ulrich-bangert.de/Racal.JPG

and perhaps anyone of  you has an idea where to get a similar one from. The
problem to find a  similar switch is perhaps easier to solve than to locate 
a
direct  replacement. Note that the scale in the photo is in cm with
subdivisions in  mm.

Best regards

Ulrich  Bangert
www.ulrich-bangert.de
Ortholzer Weg 1
27243 Gross Ippener  


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