deskthority

This was an interesting looking board I picked up - sure enough KeyTronic foam and foil. However it's a smaller board and when I mapped out the matrix it was 8 x 12 - a candidate for the xwhatsit Model F to USB - something I've been wanting to try.

As is typical the foam on several switches had degraded but most looked to be in fair condition so I went ahead to see if the xwhatsit would work with this board.
I desoldered the relevant IC's and wired the rows and columns and ground to the xwhatsit. I did quite a bit of checking and as far as I can tell, the row and column terminations are isolated from the rest of the on board controller so I left the rest of the controller components on the board.

Plugged it in and success!

The board works well with a voltage threshold of 180. A number of keys with bad foam didn't work, but all the alphabet keys except 'N' do (I've remapped the 'N' key until I replace that foam). I've started the process of replacing the foam and foil starting with the non-functioning keys - ultimately it all really needs to be replaced (tedious). The ones I've replaced are now working well. I didn't want to go though the process of replacing the foam and foil first in case the xwhatsit mod didn't work at all!

Also, although I can't detect any connections to the remaining on board controller components with my $20 multimeter, and the board seems to be working fine, I'm still a little nervous about the caps, etc. still there and may just go ahead and desolder them too. Does anyone have any thoughts about that?
It's a pretty cool old board, and fun to get it working!

Nice job! There is something about those older "hand" routed trace PCBs that just looks nice.

Great job, great looking board. GL with the fine tunning.

Gorgeous caps, and I like how there's enough buttons up top you can actually use it as a daily driver board with some creative layering.

As far as caps go, the electrolytics had a lifetime of about 10 years. The ceramic and mica ones are good basically forever. Main thing I would look for on the board since you removed the IC's is any drop resistors connected to the ground plane.

Can you tell us some more about replacing the foam? Looks like an interesting process

Sangdrax wrote: Main thing I would look for on the board since you removed the IC's is any drop resistors connected to the ground plane.

Thanks for the info!

Sangdrax wrote: Can you tell us some more about replacing the foam? Looks like an interesting process

Sure! I have developed a rather technically complex procedure that produces 7/16" x 0.20" cylinders of foam and 7/16" disks of aluminized Mylar.

First the materials:

After doing rather extensive online research into what would be the best type of foam to use, I decided on Loops&Threads brand because Walmart didn't have any foam and this was the only one on the shelf at Michael's. Similarly, I chose the Coghlan's Emergency Blanket because it was in the sporting goods department at Walmart.


A 7/16" leather punch worked well punching the foam and Mylar.


Finally, I devised an apparatus to divide the foam cylinder into 0.20" segments:
The two lines are 0.20" apart, clever right? There's also a good reason I chose blue painter's tape and a piece of purple household sponge for a backstop - they were on the counter.


The foam and emergency blanket are actually working well. I've done 15 or so keys so far and they all work. I read on the internet somewhere (so it must be true) that the KeyTronic foam was 0.20" in length and it actually does appear to be an appropriate choice.

Also, I cleaned and reused the original plastic disks from the disk/foam/foil sandwiches and just glued the new foam and foil to them (non-conductive side of the Mylar facing the PCB).

All the previously non-functioning keys are now working. Now I just need make myself go ahead and replace the original foam on the remaining keys. Otherwise, since all the original foam is in pretty rough shape, it's just a matter of time before more keys start quitting.

Good lord those traces and Keycaps are gorgeous.

Finished up with the foam and foil and using the board now.

This is what the foam was looking like:

New foam and foil in place:
Finished board:
I know some people are really down on the foam and foil switches, but I like the feel of this board. The springs are on the heavy side - I guess it's just a matter of personal preference. The spring on the "RESET" key is crazy heavy - they made sure no one was going to press that by mistake.

Now put a solenoid in it!

I agree that foam and foil isn't as bad as people hammer it for, but it's probably a result of what it was competing with at the time. A choice between it and some microswitch or honeywells and people feel like they lost the lotto when they open up some old board and find the foil instead.

Nice job on this neat looking keyboard!

Once again very nice work OldIsNew, the form-factor reminds me a bit of this Incoterm A103-06:
Here is another Westinghouse at terminals wiki:

http://terminals-wiki.org/wiki/index.ph ... stinghouse