Best replacement foam for keytronic foam and foil switches

PancakeMSTR

11 Jul 2017, 02:30

Hi,
I've got a keyboard which uses keytronic foam and foil switches and the foam (and foil, but I've got that figured out) has completely deteriorated, on every switch.

I can replace the foam pads, but I'm not quite sure what the best foam to use would be. Could anyone offer me advice? An amazon or link to some other place where I could buy the foam would be fantastic, too.

Thanks.

Parak

13 Jul 2017, 17:46

I haven't done it myself, but it'd be something of this sort:

http://vintageapple.org/lisainfo/Lukes_ ... repair.pdf

Basically pick closed cell if you want more stiffness but more durability, and open cell for the opposite. I'd probably go with the softest closed cell epdm/neoprene blend you can find of the appropriate thickness, which would be the thickness of existing pads or slightly less due to being not as compressible.

Also, go with adhesive backed foam for obvious reasons.

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XMIT
[ XMIT ]

13 Jul 2017, 18:46

Foam and foil boards get a bad reputation here. They tend to be really nice linear boards (or okay tactile boards depending on the quality of the buckling rubber sleeve used). They're also capacitive and thus, with enough love and a controller replacement, inherently NKRO. Plus, they have built in down stroke damping. There are loads of vintage boards with really nice high-profiled ABS double shot spherical key caps, that people pass on.

The trouble is that most of the foam and foil boards you'll find have corroded foam and thus will have sensing issues.

I personally pass on most foam and foil boards because I don't love linears enough and don't want to do the repair myself. but I've got a bunch of them already, and maybe one day I'll fix them up.

I would use something like Super 77 contact adhesive to glue a sheet of the mylar to the non-adhesive side of the foam, use a leather punch from the mylar side to cut the pads, prep the old surface with isopropyl alcohol, and stick them on. I'd wear gloves for all of this.

Punching foam and foil pads is no harder than punching foam for a Model F rework. Same process really.

PancakeMSTR

15 Jul 2017, 21:53

XMIT wrote: Foam and foil boards get a bad reputation here. They tend to be really nice linear boards (or okay tactile boards depending on the quality of the buckling rubber sleeve used). They're also capacitive and thus, with enough love and a controller replacement, inherently NKRO. Plus, they have built in down stroke damping. There are loads of vintage boards with really nice high-profiled ABS double shot spherical key caps, that people pass on.

The trouble is that most of the foam and foil boards you'll find have corroded foam and thus will have sensing issues.

I personally pass on most foam and foil boards because I don't love linears enough and don't want to do the repair myself. but I've got a bunch of them already, and maybe one day I'll fix them up.

I would use something like Super 77 contact adhesive to glue a sheet of the mylar to the non-adhesive side of the foam, use a leather punch from the mylar side to cut the pads, prep the old surface with isopropyl alcohol, and stick them on. I'd wear gloves for all of this.

Punching foam and foil pads is no harder than punching foam for a Model F rework. Same process really.

Yeah but what foam?

PancakeMSTR

15 Jul 2017, 21:54

Parak wrote: I haven't done it myself, but it'd be something of this sort:

http://vintageapple.org/lisainfo/Lukes_ ... repair.pdf

Basically pick closed cell if you want more stiffness but more durability, and open cell for the opposite. I'd probably go with the softest closed cell epdm/neoprene blend you can find of the appropriate thickness, which would be the thickness of existing pads or slightly less due to being not as compressible.

Also, go with adhesive backed foam for obvious reasons.
Hey thanks I'll look into that.

User avatar
seebart
Offtopicthority Instigator

15 Jul 2017, 21:57

I would NOT buy these I just wanted to show you that something like this is available:

http://www.ebay.de/itm/Victor-9000-SIRI ... Sw91NTtPPK

http://www.ebay.de/itm/Foam-Pads-for-Ke ... Sw91NTtPPK

You should be able to find more offers online make sure you know that they fit your Key Tronic keyboard these may not since they are for specific keyboards! What model is your Key Tronic?

TexElec

09 Oct 2019, 19:20

Just thought I would update this thread in case anyone else runs across it and needs to replace their foam and foil pads. We are currently making replacement pads that can be popped into place. They have been tested and used across many machines and the list is still growing. We have even had a customer repair a BTC keyboard successfully! We have been in contact with KeyTronic and even previous and current manufacturers of theirs. During this venture we were able to match our pads to an analysis completed on original pads by a metallizing company as well as matching the foam properly. :) Here is a link if you'd like to save time repairing your keyboard:

https://texelec.com/product/foam-capaci ... keytronic/

User avatar
JP!

09 Oct 2019, 19:53

TexElec wrote:
09 Oct 2019, 19:20
Just thought I would update this thread in case anyone else runs across it and needs to replace their foam and foil pads. We are currently making replacement pads that can be popped into place. They have been tested and used across many machines and the list is still growing. We have even had a customer repair a BTC keyboard successfully! We have been in contact with KeyTronic and even previous and current manufacturers of theirs. During this venture we were able to match our pads to an analysis completed on original pads by a metallizing company as well as matching the foam properly. :) Here is a link if you'd like to save time repairing your keyboard:

https://texelec.com/product/foam-capaci ... keytronic/
Thanks for sharing. I have a few boards in dire need of new foam and this looks to be a great time saver.

Also is this replacement foam superior to what was originally used?

User avatar
OldIsNew

09 Oct 2019, 22:02

I've replaced the pads on a number of boards with polyurethane cushion foam, a Mylar emergency blanket and Elmer's Craft Bond glue. It's a softer foam and I personally like the feel. I've done 7 or 8 boards now using about half of one of the two foam pads that came in the $11 package I bought and maybe a quarter of a $3.75 emergency blanket plus one $2 craft glue stick. It's tedious but I actually enjoy doing it for some reason. I guess it just depends on whether or not you feel like spending the time - if not, the texelec pads do look tempting! I put some pics of the materials I've been using on the post I put up after working on my first F&F board here : viewtopic.php?f=7&t=17294

If you do make your own pads the conductive side of the Mylar foil should face away from the PCB.

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Sangdrax

09 Oct 2019, 23:32

And you guys know I'm a fan of the hard foam. Super Glue brand precut archival grade foam tape ($1 and you need two rolls for the average full size board double stacked) and electrostatic discharge bags because they have both sides insulated and they're basically free and laying around if you do any other kind of electronic projects. Just takes an 11mm punch and about half an hour to get it done.

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mr_a500

10 Oct 2019, 00:04

I bought a set of the TexElec pads for my Victor 9000 - mostly because I am very lazy and didn't want to go through the tedium of making pads myself. So I was very happy that somebody did all that work for me and at a very reasonable cost. The replacement pads worked perfectly 100% on the very first test after installing.

One thing I did note while installing was that they were slightly thicker than the originals. I didn't think anything of it at the time, thinking that the originals were degraded, disintegrating and therefore would be thinner. When typing, however, I noticed a change in feel. The original (non-working) Victor 9000 feel was super-smooth and light, one of my all-time favourite keyboards - far nicer than my many other Key Tronic foam and foil keyboards. After the pad replacement, it felt like my least favourite Key Tronic foam and foil keyboard - too stiff. Possibly, the light & smooth feel that I liked was because the pads were degraded and it was never really that nice - or the replacement pads were slightly too thick for this keyboard, making resistance too great. Or maybe I tightened the keyboard screws too tight. Who knows?

I don't want to say anything bad about the TexElec pads because I think it's a great service they provide at a reasonable cost, helping restore many vintage keyboards that would otherwise be a pain in the ass to restore. Possibly there were variations in foam thickness for different keyboards of that era.

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Sangdrax

10 Oct 2019, 00:09

Different switch types probably had different thicknesses. The 1978 block style keytronic I'm working on right now seems like it had around 2mm pads instead of the 4'ish of the 1980's tall single switch models.

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