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Texelec's keyboard foam replacements

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    #31
    Originally posted by falter View Post
    I wonder why they didn't just subcontract the whole deal to Keytronics. I also wonder if there is much variation in the different revisions of Sol keyboard.. mine is a Rev B.

    In any event, I have been going through the first batch of foam pads and tested each on the keyboard pcb. It's interesting how some work well and others just don't. It's about 50/50. I wonder what determines whether it works or not. I would have thought given they were cut from the same material it'd be less black and white.

    The mylar ones do not work at all on mine. Not one.
    It was the same with my first batch Falter. More like 60/40 though. Some worked some didnt, no in between. I wondered if maybe on the ones that didn't work the conductive material was upside down. Seems you are making progress though. I suppose you can ask Sarah to whip you up another batch of the original material. She told me she was hand punching those however but maybe shed make the exception if you ask her.

    Comment


      #32
      I tried an experiment to prove or disprove the "dome" theory. I trimmed the edges of the aluminum/mylar disks to make them smaller. This prevented any scrubbing against the plastic housings. In baseball they call the results of this an "O-fer". Zero for 10 keys worked. So much for that theory...

      I'm still wondering about the extension of the pads when the keys are pressed and if some additional height in the pads would allow better key detection.

      After re-reading yet again some descriptions of how others have replaced the pads I'm now wondering if the thickness of the aluminum is not contributing to the problem. Many seem to have used mylar from "space blankets" and mylar balloons/wrapping material with no additional backing, minimizing the distance from the mylar to the PCB pad sites when a key is pressed.

      Comment


        #33
        i had to "trim" a few that didnt fit perfectly or were catching on the plastic. Trimming them did nothing to change whether or not they worked from the start.

        Comment


          #34
          Originally posted by falter View Post
          Yeah I don't understand at all what is going on with mine. When I repalced the pads on my Lisa it was like immediate success.

          What's strange is that some from the first batch Sara made do work. Just none from the second. So bizarre. I have to read up on how the keyboard takes care of business and then figure out what needs to be fixed. I don't know why they'd use such a convoluted system rather than simple contact switches.
          Originally posted by DaveL View Post
          I tried an experiment to prove or disprove the "dome" theory. I trimmed the edges of the aluminum/mylar disks to make them smaller. This prevented any scrubbing against the plastic housings. In baseball they call the results of this an "O-fer". Zero for 10 keys worked. So much for that theory...

          I'm still wondering about the extension of the pads when the keys are pressed and if some additional height in the pads would allow better key detection.

          After re-reading yet again some descriptions of how others have replaced the pads I'm now wondering if the thickness of the aluminum is not contributing to the problem. Many seem to have used mylar from "space blankets" and mylar balloons/wrapping material with no additional backing, minimizing the distance from the mylar to the PCB pad sites when a key is pressed.
          Originally posted by VERAULT View Post
          i had to "trim" a few that didnt fit perfectly or were catching on the plastic. Trimming them did nothing to change whether or not they worked from the start.
          Hey guys!

          I have had to trim some myself as I use ones from my reject pile. I don’t like to use my “sellable stock” for myself too often except when testing. The dome that happens sometimes, is just unavoidable, but it doesn’t seem to make a difference for me versus the ones that come out perfectly flat. Just like with Falter’s Lisa and Verault’s Compaq. I have pulled a few that are slightly domed as well as flat from my stock. Here are some photos showing how much they stick up from my Compaq as well as just sitting free:
          https://texelec.com/wp-content/uploa...-samples-2.jpg
          https://texelec.com/wp-content/uploa...-samples-1.jpg
          https://texelec.com/wp-content/uploa...n-compaq-1.jpg

          I don’t have much use for the double height pad in my situation. Once the PCB is attached it is directly against the top of the frame of each key, meaning the PCB sits on the frame all the time. It even screws into some of the holes in the corner of the keys. Having double height pads on it would mean the key cannot be pressed all the way in without pressure and it would compress the pad when pressed all the way.
          https://texelec.com/wp-content/uploa...n-compaq-2.jpg

          Falter: I have a bag of rejects with the old material that I have been adding to since my hammering days. If you’d like that bag I’d be glad to send it your way. I have attached photos, some are actually “sellable stock”. Keep in mind, some of them are a real mess and I may have never used them anyway. It was just faster quality control for me to throw all bad ones in one bag. I was mid bag when I started getting feedback about failing pads in Lisa machines and then Verault told me about his 60/40 issue, so I never finished that bag. I could also make you a bag with the old material and I also have another set of bags I considered using that is a bit more reflective. But note, neither of these materials pass an ohm test on either side. I guess they are just mylar coated on both sides with thin aluminum inside? This would explain why they sort of work. I always pasted those down with the inside of the bag toward the foam This was after cutting apart 12”x16” bags I still have a use for the cards we build. You could also try pasting a space blanket to some of the non-working pads or even kitchen foil to see if that helps. I did have some people tell me they just did that instead of getting replacements, but again, this was not on a SOL. Maybe even cutting up an anti-static bag would work better for you since those seem to be working for you? Do you have any double stick tape? A 7/16” leather punch tools would also be handy. You can get them cheap from Harbor Freight or maybe even Amazon. The 16th and 17th is Prime Day. Unfortunately, you will likely have to buy a set, but they are super cheap.
          https://texelec.com/wp-content/uploa.../old-bag-1.jpg
          https://texelec.com/wp-content/uploa.../old-bag-2.jpg
          https://texelec.com/wp-content/uploa.../old-bag-3.jpg
          https://texelec.com/wp-content/uploa.../old-bag-4.jpg
          https://texelec.com/wp-content/uploa.../old-bag-5.jpg
          Punch set: https://www.amazon.com/SE-790LP-Leat...SIN=B001F27AMI

          I also have a bag of aluminum plated mylar rejects if that will help either of you:
          https://texelec.com/wp-content/uploa.../new-bag-1.jpg
          https://texelec.com/wp-content/uploa.../new-bag-2.jpg


          DavidL: Have you tried moving the ones that DO work reliably from those spots and putting them in the spots that DO NOT work reliably? It seems like that would tell you if it’s the PCB vs the pad and solve the height question. I know that all this testing starts circling and doubt starts forming after hours of clicking these pads in and out. Let me know if you need a second bag!

          I don’t know that the thickness of the mylar is an issue. I have seen people use wrapping paper, kitchen foil space blankets, mylar balloons and something called “party foil” from the craft store. All of these materials are different thicknesses. I would think the mylar balloons would be the thickest or possibly the foiled wrapping paper and the space blanket would be the thinnest. Plus, the static bags I was using were 3 mil and the aluminum plated mylar I use now is 2 mil. However, I wouldn’t know for certain without testing all of these on a SOL. I don’t think my Compaq cares about these very small differences. I could send you a second bag as well. I’m willing to work with you guys to get this solved.

          It seems like I may just have to drop support for the SOL at this point, however I hate to do that immediately. There doesn’t seem to be a uniform pattern as to why they are failing between the two of you. I’d be happy to borrow a SOL for testing and send it back to someone. �� Preferably someone in the states. Maybe my other SOL user will chime in sooner than later. He did get back to me and said he hasn’t tried them yet so maybe he will have time soon. For now, I may just make a note in my listings that they have not worked on a SOL reliably yet, I need more feedback and that's the only way I know how to get it, sell more of them. Maybe one of the users in the Lisa group could chime in as well. I’ll have to check.

          I would like for these pads to work for all KeyTronics so I am not giving up quite yet, obviously!

          Comment


            #35
            Sarah, if you ever need someone to test either original or Mylar let me know. I have a few more keyboards to rebuild. "hint hint, super obvious" I feel this is progress towards achieving a real replacement for our legacy hardware.

            Comment


              #36
              Originally posted by sarawill View Post
              A link to the Apple Lisa group (which is a closed group so you will need to join) post is below and in those comments you will also find a man who made his own pads and used them on Lisa’s, SOL-20s, Hyperions and a TRS-80, they were all the same pads.
              That would be me I did spend a little time trying to figure out the right material, especially for the foam portion of the pads. Sounds like I got lucky with the shiny mylar "foil" as it was dollar store wrapping paper. One side has a mirror finish and the other side is green (looks like it was applied to the other originally shiny side). Neither side of this flimsy wrapping paper has any hint of conductivity or resistance so I originally didn't think it would work but it does on anything I've tried so far. I started with the SOL-20. Here's my old post with a link to the weather stripping that no longer works.

              Foam and foil - foil.jpg

              Sadly, the weather stripping that I finally selected for the foam is no longer available at the hardware store I bought it at. I am not 100% certain but I believe it was 1/4" thick by 1/2" wide by 35 feet long. 1/4" thick is slightly thicker but it was not too much thicker. The picture below has a real - new old stock Keytronic foam and foil disk on the left and my homemade version on the right. You can see the slight height difference.

              Foam and Foil real vs mine.jpg

              It's 1/2" wide because I used a 7/8" punch and hand punched them out. I used a wood backing so that it was soft for the punch. You might notice some slight saw dust in the foam

              I chose open celled low-density foam because of key feel and it's closest to the original material. I actually tried closed cell foam but it's like trying to press down on several balloon as opposed to the open cell nature that collapses much better giving a lighter feel as there is less downward resistance. High density foam was too dense and was stiff. To be honest, I don't know how long the foam I selected will last but replacing these again is inevitable. I've seen closed cell foam in IBM 5100s turn to a tar like substance (and that is a mess to clean up) so one never knows what to expect with any foam.

              I don't have many extra foam and foil disks left but how about I send Sara and Falter five disks each?

              Sara, you can check out my materials and construction. I don't have any weather stripping chunks left but I can send you a scrap of "foil". It's really thin. If you would send me five disks, I can check out your construction. If you want to send me a set, I can try it out on a Sol-20. PM me.

              Falter, I'd be happy to send you five disks and you can try them out and see if it makes any difference. PM me.

              Be warned, I made lots of these and the few that I have left are crooked and not exactly showroom condition but they work just the same. I just have to trim them because sometimes they are crooked enough to touch the sides of the key housing. I still use these myself when I need to.

              As for the "dome effect", this is normal and doesn't affect operation in my experience. I have many that are domed and they work just fine for me. I actually like the look of that

              Hope this helps.

              P.S. Sara, I have no idea why you would need "double height" key pads. All of mine are all the same thickness. I have never seen keyboards that required them. If you know of a particular model, let me know.
              Maintainer of http://vintagecomputer.ca

              Comment


                #37
                In the event, I went through all of the pads I bought from the first order, and tested each manually with the keyboard. I had originally ordered two bags, by the time I tested them all I had just enough to do the complete Sol keyboard... probably about a 50% success rate.


                Works great with the good ones installed.. except for some reason it needs 5 minutes to 'warm up' before the computer will recognize anything typed. I suspect the problem is on the motherboard somewhere. But yeah.. about half the first batch worked with mine. No idea why the other half and the whole second batch did not.

                Comment


                  #38
                  Originally posted by snuci View Post
                  That would be me I did spend a little time trying to figure out the right material, especially for the foam portion of the pads. Sounds like I got lucky with the shiny mylar "foil" as it was dollar store wrapping paper. One side has a mirror finish and the other side is green (looks like it was applied to the other originally shiny side). Neither side of this flimsy wrapping paper has any hint of conductivity or resistance so I originally didn't think it would work but it does on anything I've tried so far. I started with the SOL-20. Here's my old post with a link to the weather stripping that no longer works.

                  [ATTACH=CONFIG]46814[/ATTACH]

                  Sadly, the weather stripping that I finally selected for the foam is no longer available at the hardware store I bought it at. I am not 100% certain but I believe it was 1/4" thick by 1/2" wide by 35 feet long. 1/4" thick is slightly thicker but it was not too much thicker. The picture below has a real - new old stock Keytronic foam and foil disk on the left and my homemade version on the right. You can see the slight height difference.

                  [ATTACH=CONFIG]46815[/ATTACH]

                  It's 1/2" wide because I used a 7/8" punch and hand punched them out. I used a wood backing so that it was soft for the punch. You might notice some slight saw dust in the foam

                  I chose open celled low-density foam because of key feel and it's closest to the original material. I actually tried closed cell foam but it's like trying to press down on several balloon as opposed to the open cell nature that collapses much better giving a lighter feel as there is less downward resistance. High density foam was too dense and was stiff. To be honest, I don't know how long the foam I selected will last but replacing these again is inevitable. I've seen closed cell foam in IBM 5100s turn to a tar like substance (and that is a mess to clean up) so one never knows what to expect with any foam.

                  I don't have many extra foam and foil disks left but how about I send Sara and Falter five disks each?

                  Sara, you can check out my materials and construction. I don't have any weather stripping chunks left but I can send you a scrap of "foil". It's really thin. If you would send me five disks, I can check out your construction. If you want to send me a set, I can try it out on a Sol-20. PM me.

                  Falter, I'd be happy to send you five disks and you can try them out and see if it makes any difference. PM me.

                  Be warned, I made lots of these and the few that I have left are crooked and not exactly showroom condition but they work just the same. I just have to trim them because sometimes they are crooked enough to touch the sides of the key housing. I still use these myself when I need to.

                  As for the "dome effect", this is normal and doesn't affect operation in my experience. I have many that are domed and they work just fine for me. I actually like the look of that

                  Hope this helps.

                  P.S. Sara, I have no idea why you would need "double height" key pads. All of mine are all the same thickness. I have never seen keyboards that required them. If you know of a particular model, let me know.
                  Originally posted by falter View Post
                  In the event, I went through all of the pads I bought from the first order, and tested each manually with the keyboard. I had originally ordered two bags, by the time I tested them all I had just enough to do the complete Sol keyboard... probably about a 50% success rate.


                  Works great with the good ones installed.. except for some reason it needs 5 minutes to 'warm up' before the computer will recognize anything typed. I suspect the problem is on the motherboard somewhere. But yeah.. about half the first batch worked with mine. No idea why the other half and the whole second batch did not.
                  Snuci: The double height are supposed to be for the deeper set mechanical Caps Lock key on the Lisa's. Both the Lisa guys that I was working with from the Apple group tested them in that key on the Lisa. Well I say that, JJ made his own from two of my pads from the "bad material", this is what prompted me to make them. Jeremy actually tested the ones I now provide in each bag. I don't have a Lisa myself but they did use them so I assume they are needed for Lisa machines. I just provide them each bag in case people are buying for a Lisa. I'll PM you, I'd love another SOL test on a known good machine!

                  Falter: So the new aluminum plated mylar pads ARE working for you now? Is that what I just heard? Sorry, I'm in shock over here so I need to hear it again.

                  Comment


                    #39
                    Originally posted by sarawill View Post
                    Snuci: The double height are supposed to be for the deeper set mechanical Caps Lock key on the Lisa's. Both the Lisa guys that I was working with from the Apple group tested them in that key on the Lisa.
                    I have five or six Lisa keyboards. I replaced the pads in at least three or four (if not all). Out of curiosity, I will check them. Hopefully I didn't replace the pads in one of them yet and I'll see if there is a difference on the Caps Lock. This picture of one of my Lisa keyboards has my homemade pads in it already. They aren't perfect and the domes are quite apparent but they work perfectly fine. At the right most side of the picture is the Caps Lock key with the white plastic surround. I would have put a normal pad in there. Of note, there were variations of the keyboard for the Lisa so they are not all the same. Has anyone else experienced the need for a different pad on Caps Lock?

                    Apple_A6MB101_bottom_key_switch_profile.jpg
                    Maintainer of http://vintagecomputer.ca

                    Comment


                      #40
                      Originally posted by sarawill View Post
                      Snuci: The double height are supposed to be for the deeper set mechanical Caps Lock key on the Lisa's. Both the Lisa guys that I was working with from the Apple group tested them in that key on the Lisa. Well I say that, JJ made his own from two of my pads from the "bad material", this is what prompted me to make them. Jeremy actually tested the ones I now provide in each bag. I don't have a Lisa myself but they did use them so I assume they are needed for Lisa machines. I just provide them each bag in case people are buying for a Lisa. I'll PM you, I'd love another SOL test on a known good machine!

                      Falter: So the new aluminum plated mylar pads ARE working for you now? Is that what I just heard? Sorry, I'm in shock over here so I need to hear it again.
                      About half of the first batch of pads you sent me (the ones with the blue coloured discs on one side) worked for some reason. None of the shiny foil ones have worked with mine so far.

                      Comment


                        #41
                        Some one might have done this already, but, it's worth mentioning.

                        Any time we have to clean contacts (like on keyboards or card-edges or what have you) we just use the pink eraser on the end of a pencil. It seems great at taking off tarnish, oils and most contaminants and very lightly burnishes the surface. It's cheap, usually right at hand and what have you got to lose?
                        Legacy Computers and Parts

                        Sales of, parts for, and repairs to, Vintage and Legacy computers.

                        Comment


                          #42
                          Originally posted by Druid6900 View Post
                          what have you got to lose?
                          What's a little graphite contamination amongst friends.

                          https://electronics.stackexchange.co...with-an-eraser

                          Comment


                            #43
                            After spending some quality time with the pads, calipers, a scope, and the analog mux U19 I believe the fundamental problem is the thickness of the pads. I measured the pads at ~3.5 mm but there's variance because not all of them are perfectly flat (I believe a slight slope of the mylar/aluminum becomes important). Further, unpressed, a key's "plunger" is 8 mm from the lower edge of the key's housing (and hence, the keyboard PCB). When pressed, a key's plunger travels 5 mm, leaving 3 mm to the PCB that must be accounted for by the pad, which must then apply enough pressure to the mylar/aluminum to create enough capacitance to be detected. 0.5 mm isn't a lot of margin for error, especially for pads that aren't perfectly flat (i.e., have some slope). The visual difference between mostly working (left) and non-working (right) can be seen in the attached photo.

                            (A theory about a sloped pad is that while it may ultimately present enough of a capacitance change it does so in a fashion that it gets rejected as spurious by the sense amp and downstream logic. Just a thought...)

                            Scoping the inputs and output of the analog mux at U19 showed that as a key is depressed the magnitude of the pulses propagated to the sense amp vary significantly depending on how far the key is depressed. If the key is bottomed out you'll (of course) get maximum capacitance and a pulse the sense amp may (or may not) accept as a valid keypress. Keys with the better-acting pads (similar to the one on the left in the photo) more reliably produced detectable pulses while ones similar to the pad on the right rarely (or never) produced pulses with enough magnitude to be detected.

                            I think the fundamental problem is the ~3.5 mm height of the pads. They should probably be 4-4.5 mm instead. The double-height pads I tried are too tall (too stiff when their key is pressed) and sloped so I believe they end up having their keypresses rejected by the logic downstream of the sense amps.

                            Thoughts?
                            WhichOneWorks_1.jpg
                            Last edited by DaveL; July 21, 2018, 07:25 PM.

                            Comment


                              #44
                              Haha, I think Al's been holding out on us! This post from 2013 (elaborated on here recently) has what I think is the very best answer for foam (because it very closely matches the original open-cell design): Woodland Scenics 5mm HO Track-Bed

                              I'd suggest that the best overall fix would be to combine Sara's outer layers with the 5mm Track-Bed foam.
                              Last edited by DaveL; July 22, 2018, 03:57 PM.

                              Comment


                                #45
                                I concur on the foam. Both the height and density of it seem to be an issue. After assembling a working set I'm left with a few that work inconsistently and it seems to be the height of the foam that is the issue. The slope also creates some alignment and fitment issues, although some slope may be unavoidable if you're doing 'mass' production.

                                Sara did some really nice work overall. I had heard of that track bed stuff being used before.. funny I forgot that as I'm also a railway modeler. I'm kind of curious if the batches of pads I bought for my Lisa years ago used that or were spare originals. They had that texture of foam.. it's very light but responsive. But it was green rather than black. Can't think of why one would want green trackbed.

                                Comment

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