Racal repair idea--quick!

[eevcandies]

I recently got a Racal 1996 counter (options 01 & 4E) for about $99.  It was in pristine shape, but of course, almost all of the buttons were junk (I own several other Racals, all working good).
I decided, finally, to replace all of the buttons.  I ordered the buttons, then kept putting it off--since I hate the thought of desoldering 40 buttons.

Then I had a Great idea--I set up my electronic solder tweezers to match the spacing of the switch leads  (see photo).  Since it awkward to pull switches without 3 hands, it is MUCH better to put the tweezers in a vise & move the board around to heat the desired switch--heating both leads together, lets you yank out the switch in about 8 seconds.  I pulled all of the switches in record time.

Now the 80 holes were kinda clogged up.  I broke out my vacuum desoldering "iron" and sucked out a pile of via solder in about 15 minutes.   
Then I installed the switches which fit in place perfectly---they were the same size, shape & lead spacing.  Put in about 6 switches (about as many as I could and flip the board), tacked soldered one lead so they wouldn't fall out, then when back, melted & fully seated each switch & soldered the 2nd leads of each.  Important each switch is flush to the PCB. Repeated this process, till all were in.  They all have a nice detent "click" like the originals.

I did some cleanup & reassembly.  Since the "T-shaped"  stalk on these switches is slightly thinner than the Racal version,  the switch caps fit great, but would somewhat easily fall off.  I used a drop of automotive  weatherstrip glue to keep each in place.  I wanted something tacky/sticky...not a "hard" glue that would eventually crack & fall apart from all the pressing.

The finished result looks as good as new!

 



 

[bitseeker]

Fantastic. Sounds like a great method. Do post more info about the switches that worked so well. I wonder if they'd work on the 1991 and 1992. I can't tell from the service manual because part number formats are completely different.

[eevcandies]

I took a look at all of the old switches...all of them had the little rubber part with the center cracked & hardened...so that seems to the common culprit.  Maybe spraying them with some  ArmourAll before they fail would keep them flexible & stop this from happening.

[bitseeker]

Yes, the rubber gasket is the common failure for these. What is the manufacturer and model of the switches you used for your 1996?

[eevcandies]

The switch is a SKEGACA010  by ALPS.  It is a perfect fit for the PCB holes & switch housing height.  It has a just-barely-noticable detent "click" when pressed.   The caps fit on fine, but slightly loose.

The stem travel is slightly offset compared to the original, so the button caps themselves stick out of the panel by approx 1mm more than original--which is rather minimal & wouldn't look bad when replacing 1 or 2 switches.  Or, you could file the stem 1mm pretty easy!  The drop of glue could be causing the 1mm difference. Use a gummy/tacky glue & the caps will stay right on.

Of course, if replacing every switch, height variation becomes invisible-- my pictures speak for themselves

I got 100 of these for about $24, plus few bucks shipping.

. 

[bitseeker]

Sounds great to me!

Here's a datasheet: https://www.mouser.com/datasheet/2/15/SKEG-1371040.pdf

[eevcandies]

Forget Mouser..they want like 0.75 each!!!...everywhere else MUCH cheaper.
Master parts is cheap, but they say $50 min order...Online components direct seems to be the same place (same address & same quan in stock & same price)...but no min $ order...go figure!!

[bitseeker]

It was just the first place I found the datasheet. I agree, it's really expensive there.

[basinstreetdesign]

 

[eevcandies]

There is a youtube video where switches were replaced...but those replacement switches (some black ones??), seemed quite much taller, and wanted to hit the panel (nearly causing them to become pressed).  The keycaps also stuck waaaay out.  This switch avoids those issues.

[bd139]

Interesting thread. I have been avoiding that series of Racal counters as literally every one I've seen at a hamfest is "working apart from a couple of buttons". Problem solved. Now just need to haggle them down 

[eevcandies]

maybe make a lowball offer...note this unit does not have the 1.3GHz input
https://www.ebay.com/itm/RACAL-DANA-1991-nanosecond-universal-counter-For-Parts-Not-Working/173899488850?epid=1690625083&hash=item287d379e52:g:UrIAAOSwZqRc1f-g

[bitseeker]

There is a youtube video where switches were replaced...but those replacement switches (some black ones??), seemed quite much taller, and wanted to hit the panel (nearly causing them to become pressed).  The keycaps also stuck waaaay out.  This switch avoids those issues.

I think you may be referring to Defpom's repair, but there may have been a different one I saw after that. Dimensions of the shaft and the top of it were definitely an issue until you found this model.

I have two 1992. One has all good buttons. The other...doesn't. However, it doesn't boot properly. When I get around to making it run again, I'll do the switches.

[eevcandies]

I've got two perfect working 1996's & one 1992.  I also have another 1996 that was working fine, then got slightly fritzy (perhaps bad key?).  I have another 1992 that I partly disassembled for some reason & sits on a shelf for past 8 years...maybe time to do some repair!   A few weeks back there were a bunch of 1992's on ebay for $80-$100...I wanted to have buy buy buy fever, but sanity took over & I let them pass by.

[bitseeker]

Haha! Yes, it can happen, especially once you're familiar with the ailments of a particular model or line of test gear.

[eevcandies]

I have two 1992. One has all good buttons. The other...doesn't. However, it doesn't boot properly. When I get around to making it run again, I'll do the switches.

The "boot problem"  could be switches that are defective & pressing down...if you hold down a bunch of switches during power up, you can get errors and all kinds of mayhem.

Maybe try swapping control panels as a sanity check...they are very easy to remove (10 minutes).

[bitseeker]

Oh, good idea. Totally makes sense. I'll have to try that (perhaps this weekend).

[eevcandies]

Update...the switches were very cheap...

SKEGACA010 Alps Electric
Switch Tactile N.O. SPST Button PC Pins 0.005A 12VDC 0.78N Thru-H...    Item Price: $0.236
Quantity: 100
   100 Ships 04/29/2019   Line Total: $23.60

now in May 2022 they are gouging: 100 switches from same supplier will be around $93

[mapleLC]

Interesting, I have a 1991.  This is good to know.

[thinkfat]

I have a 1998. Good to know should any of the switches fail.

But, I have to say, this is one seriously messybusy bench!

Approved!

[Gertjan]

I used the info in this topic to successfully replace the switches in my Racal-Dana 1992.

I am very happy with the result! The look and feel of the replacement switches is just the same as with the original ones. (That is, before they broke down )
I wrote a report with photos on Dutch language forum Circuits Online. (The photos will tell most of the story)

A few Photos showing the differences between the original switch, and the ALPS SKEGACA010 replacement switch. (Original switch on the left, replacement on the right):


IMG 1700  Racal schaks vervangen - oude naast nieuwe schakelaar-2000pix.jpg

The same, but now with a Racal-Dana knob:


IMG 1701  Racal schaks vervangen - oude naast nieuwe schakelaar met knop-2000pix.jpg

A better view of the stem of the switch:


IMG 1712  Racal schaks vervangen - oude naast nieuwe schakelaar stem profiel-2000pix.jpg

In front of the switches is a Racal-Dana knob, that should fit on the switch.
(With apologies voor the photo titles in Dutch )

Many thanks to eevcandies, who did the hard work to find the replacement switch!
Hopefully, many more of these very nice counters will get another lease of life, with perfect fitting switches.

Regards, Gertjan.