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Texelec's keyboard foam replacements

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    #16
    Originally posted by falter View Post
    But a conductivity test shows no conductivity at all.
    There is not supposed to be any conductivity. The silver disk on the pad acts as a capacitor, hence why these are called capacitive keyboards.

    It is possible that different keyboards are designed for different capacitance values, but that would mean their original pads would have had to use a different material than other capacitive keyboards.

    Do you still have any of the original silver disks that came with your keyboard? I'd try attaching one to something besides a finger and making sure it still recognizes those. It is possible it could be slightly damaged and out of spec even though a higher capacitance material might allow it to work.

    Anyway, that is a bit disappointing to hear as I recently acquired another capacitive keyboard that needs new foam pads.

    Comment


      #17
      Originally posted by falter View Post
      Unfortunately they did not work at all this time.Whereas the previous batch sort of worked, my Sol doesn't react to these at all. And I have verified the keyboard is in fact working. If I use my fingertip, or if I take one of the pads from the first batch and press it to the contact manually, the Sol reacts. But the new ones, nope. Not even a little
      Falter, I bought these to repair a couple compaq portables. I did the same thing as you. The pcb worked when I used my bare finger. Out of the first Batch of texelecs pads, 44 didnt work. I tested every single one between my fingertips and the pcb. They would either work or not work.. there was no grey area. The new ones Sarah sent all worked for me, and yes they were a new material. I am wondering what the requirements or tolerances are for your SOL keyboard compared to the original compaq portable.

      You tried every single pad and not one worked? Did you clean each contact of possible corrosion? I did as the contact pads on the PCB are not gold, but tin maybe and had some slight corrosion. I use this eraser as it contatins sand to clean all card edge connections and corrosion: https://www.ebay.com/itm/Mono-Sand-E...sid=m570.l1313

      Comment


        #18
        Originally posted by SomeGuy View Post
        There is not supposed to be any conductivity.
        The problem was she wasn't using aluminized mylar, and the originals conduct ON THE ALUMIZED SIDE
        There was no conductivity on the side which is SUPPOSED to be conductive ACROSS THE PAD, NOT THROUGH IT.
        Measure an original pad yourself!

        That side gets glued to the foam and forms one side of the capacitor

        Comment


          #19
          Originally posted by Al Kossow View Post
          Tthe originals conduct ON THE ALUMIZED SIDE
          Ooops, I totally forgot about that. Thanks for the clarification.

          Comment


            #20
            So is the verdict that the post-July 4 pads actually don't work in a Sol? If this is true, does anyone have a source for replacement pads that will work in a Sol?

            Comment


              #21
              So if I've read Al's comment correctly, if I were to remove the shiny material from one of these foam replacements, on the shiny side I'd have no conductivity but on the side that was glued to the foam there would be conductivity? I took one foam pad apart, scraped away the foam residue on the glued side and tried a conductivity test... nothing on either side of the 'mylar' or whatever the shiny stuff used is.

              Does this suggest there's something wrong with my keyboard since mine seems to prefer having the conductive side contact the PCB?

              Sorry if I'm misunderstanding what's been said. I'm just wanting to clarify if I have a defect with the pads or the Sol itself.
              Last edited by falter; July 13, 2018, 07:26 AM.

              Comment


                #22
                Originally posted by DaveL View Post
                So is the verdict that the post-July 4 pads actually don't work in a Sol? If this is true, does anyone have a source for replacement pads that will work in a Sol?
                Originally posted by falter View Post
                So if I've read Al's comment correctly, if I were to remove the shiny material from one of these foam replacements, on the shiny side I'd have no conductivity but on the side that was glued to the foam there would be conductivity? I took one foam pad apart, scraped away the foam residue on the glued side and tried a conductivity test... nothing on either side of the 'mylar' or whatever the shiny stuff used is.

                Does this suggest there's something wrong with my keyboard since mine seems to prefer having the conductive side contact the PCB?

                Sorry if I'm misunderstanding what's been said. I'm just wanting to clarify if I have a defect with the pads or the Sol itself.
                Hello again everyone,

                The conductive side (or metal/aluminum plated side) is supposed to be the side that is glued to the foam and the capacitive side faces the board/PCB. That is how they are put together.
                So yes, trying to do an ohm test on the bottom of the pad will not show any results. The inside of the pad will pass an ohm test. However, trying to disassemble one will likely not work unless you are able to get all of the glue and foam left behind off. I just tried that myself and I also tried just sticking the probes in the pad against the aluminum side and it shows no reading. You have to conduct the test on clean material. Even if you tried to clean all the foam with something like rubbing alcohol it would also likely not pass an ohm test. If you could manage to get that dense foam and the glue off it would possibly also remove the aluminum plating from the mylar.

                Here’s how I know this. On my very first batch of pads with this new material I actually did glue the mylar side down to the foam pad leaving the aluminum plating outward to touch the board. This is because I did an initial finger test (meaning I put the aluminum plated mylar on my finger and touched it to my Compaq board) and it responded wonderfully! I turned it to the mylar side and got nothing, well nothing consistent anyway. I could barely touch the metal plated side to the board and it would register a reading. I could swoop it across and make it dance on that board and it would register a reading meaning it would deliver a character to the screen. I thought, “WOW THIS IS AWESOME! Nothing like that old material I was using.” Which was, by the way, static bag material. I tested it the same way before I made pads and the static bag was never this “sensitive”. So I made a batch and installed them in my Compaq. I also spattered a heavy amount of glue on parts of the outside as it was windy outside and tried cleaning it with rubbing alcohol in those spots. I had to scrub it a lot. All the pads seemed to work great except for those that I cleaned too much…OR SO I THOUGHT! However, sometimes key presses would register multiple characters to the screen, I didn’t know what was happening, I just thought there was something else going on with my Compaq. So I made another batch so I could send them to my Lisa tester. I then tell him all about what I have done and how excited I am about how it is so sensitive, and this is what he tells me:

                “Keep in mind that these are capacitive keyboards, not conductive. This means that the plastic side of the sheet needs to be outwards, touching the PCB. If you flip the conductive side towards the PCB, it will wear off quite quickly. Also, using your finger to press it onto the PCB isn't a good test, as your finger adds capacitance the same way an iPhone screen detects your finger. Gluing a piece to a pencil eraser would be a great test.”

                I then respond be asking about how long it will last and dissatisfied because I want these to last forever! So he is, again, very patient with me and explains even more. Also, keep in mind, I already had some other nice gentlemen telling me all of this on the Apple Lisa group on Facebook prior to my first batch. I just wasn’t getting it! He says this:

                “Yes. On a capacitive pad, you want only the plastic to touch the PCB. The metal on the other side acts as a capacitor, which the keyboard senses. It may work for a little while if flipped around, but the metal can wear off. Not just Lisa's, but all the Key Tronic keyboards should have the plastic side outwards. Some keyboards are just more sensitive to the materials than others. If we can find a good material that works well in the Lisa, it should work on all other keyboards also.”

                He also sent me this nifty diagram: https://texelec.com/wp-content/uploa...ad-Diagram.png

                He then added this:

                “Use a multimeter on the lowest resistance (ohms) setting. You'll find that one side is conductive, that's the metal side. The other side is not conductive, that's the plastic side.”

                So I did and I just made a video doing this test for you on the material I am using on the pads. I tried tearing apart a pre-assembled pad but it is not showing a reading through the left over foam and glue so here it is before assembly: https://texelec.com/wp-content/uploa...r-OHM-Test.mp4

                I also did an ohm test on an original pad from my Compaq. The foam was still decent, and the glue was holding on pretty well so I didn’t scrub it too much as I didn’t want to remove any of the plating so the reading isn’t as strong as it would be on clean material: https://texelec.com/wp-content/uploa...q-OHM-Test.mp4

                I have heard back from my Lisa tester, who ended up being a different customer than the nice gentleman that helped me SO MUCH during construction. He just got too busy to work on his Lisa so I got someone else to get it tested for me. He was very thorough and had some critiques on the foam being more dense than the original. He only mentions this because he knows purists out there will want the same feel when hitting the keys which I understand. I like this foam because it will have an overall longer shelf life than open cell foam, I mention all of this in my blog post. Anyway, he did verify that every single pad worked, unlike the static bag material which was hit or miss for him as well. This is what he said on the Lisa group:

                “I tested them in my Lisa keyboard, they all worked great. I have rebuilt a number of keyboards, at least 7 or 8. I think Sara's pads are the best option available. I usually purchase the foam pads, then build them myself, using the old parts from the degraded original pads. Unfortunately, the shipping alone for those foam pads is about $20. In addition, a lot of the time, the silvery colored mylar, is worn completely off. So, the old parts can't be used.”

                I also heard back from Verault, who has posted on this thread as well and said every single pad worked, again, unlike the static bag material. I have received feedback from people on eBay as well but only 3 people (including Verault) mention the actual product. I think people order these and don’t get them installed right away. I really hope I will hear back from more people soon. I have sent all replacements out up to this point so maybe more from the Lisa group and eBay will give me feedback. Here is a link to my eBay feedback: https://feedback.ebay.com/ws/eBayISA...?ViewFeedback2

                Here is a link to my blog post where I talk all about the saga of the foam pads but there I did not go into all this capacitive/conductive detail. It was more an overall story from the original material I used and the final Lisa testing with the aluminum plated mylar. It also discusses other computers that the guys from the Lisa group were telling me about that used KeyTronic “foam and foil” pads: https://texelec.com/2018/07/04/new-a...nic-keyboards/

                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. You will also see others explaining the capacitive versus the conductive sides on the post comments: https://www.facebook.com/groups/1456...2704983662249/

                Here is a Deskthority article talking about KeyTronics keyboards that use the “foam and foil” capacitive pads: https://deskthority.net/wiki/Key_Tronic_foam_and_foil

                Here is a page that I hope will be updated someday to include my premade capacitive pads because there is a replacement available now that doesn’t include all the cleaning, cutting, punching and gluing! Maybe someday, one can hope. http://sol20.org/keyboard.html

                I started making these because of many articles I read about cutting foam gluing old plastic and using aluminum foil, mylar balloons, foiled wrapping paper, space blankets, etc. and painstakingly removing old materials and cleaning and gluing...and so on. I purchased a punch set and started making my own to fix old terminals and Compaq Portables as well as a Tandy or two along the way. You’ll see if you read my blog post.

                Falter, I can’t help but think that your keyboard does have an issue outside of the foam pads needing to be replaced and I really hope that my very long-winded comment here has helped you understand the construction of the “foam and foil” pads and how they work. I know that I learned a lot myself in this process.

                DavidL, if you were to buy a set of pads to fix your SOL I would be happy to accept a return if they did not work out for you and I would appreciate the testing on a SOL! I contacted a customer of mine earlier today when I read these new comments that I KNOW is going to be replacing his pads in a SOL. I will be happy to let you know when/if I hear back from him. He may even comment on this thread as he appears to have previously commented on this thread already.

                Comment


                  #23
                  After installing the post-July 4 TexElec pads in one of my Sol-20's I can report that they do indeed work! There are a few keys that aren't yet playing nice but I suspect I need to clean some the PC board's pad sites. A number of keys didn't appear to work at first but with some repeated use they seemed to get better. I think that points back to cleaning but I'll check the more problematic keys to ensure the replacement pads are installed correctly and aren't deformed. During installation I was careful to pick out the most pristine pads.

                  I believe falter's keyboard is actually a little faltery.

                  Sara, thanks for hanging with us on this. It's sometimes "challenging" to get this cranky old stuff to go once again but it looks like yours is a good solution.

                  Comment


                    #24
                    Originally posted by DaveL View Post
                    After installing the post-July 4 TexElec pads in one of my Sol-20's I can report that they do indeed work! There are a few keys that aren't yet playing nice but I suspect I need to clean some the PC board's pad sites. A number of keys didn't appear to work at first but with some repeated use they seemed to get better. I think that points back to cleaning but I'll check the more problematic keys to ensure the replacement pads are installed correctly and aren't deformed. During installation I was careful to pick out the most pristine pads.

                    I believe falter's keyboard is actually a little faltery.

                    Sara, thanks for hanging with us on this. It's sometimes "challenging" to get this cranky old stuff to go once again but it looks like yours is a good solution.
                    DaveL, that is excellent news! HOORAY! I actually just did a little jump for joy over here! Thank you VERY MUCH for the update! I do hope falter gets his SOL working. I have to admit I'm a little jealous, those are sweet looking machines!

                    Comment


                      #25
                      Thanks Sara! Yes, that definitely helps a lot. Now i know that I need to target my Sol a bit more and figure out what's going on here. I note that my Sol takes a good 2-3 minutes to warm up before it even notices any keypresses - foam pads or finger. Some have suggested solder problems, etc. Now that Dave has confirmed your pads work, I'm all good and will figure this out! Thank you again for the explanation and excellent customer service!

                      Comment


                        #26
                        Originally posted by falter View Post
                        Thanks Sara! Yes, that definitely helps a lot. Now i know that I need to target my Sol a bit more and figure out what's going on here. I note that my Sol takes a good 2-3 minutes to warm up before it even notices any keypresses - foam pads or finger. Some have suggested solder problems, etc. Now that Dave has confirmed your pads work, I'm all good and will figure this out! Thank you again for the explanation and excellent customer service!
                        No problem falter. I hope you get it up and running, she's a beauty! Best of luck to you!

                        Comment


                          #27
                          Well, we may not be quite golden yet. After cleaning all the pad sites on the PCB, trimming the power supply so that there's exactly 5V at the keyboard-side ribbon connector, re-seating some pads that I didn't mount correctly the first time (must listen for the little clicks!), and swapping out a couple pads that weren't as pretty as the others I still have keys that aren't first-time-every-time reliable and a few that still won't register at all. (Please note: All the pad sites will register if I do the "finger test" or use one of the pads mounted at the end of a plastic screwdriver handle, so I don't believe there's any electronic issue with the PCB.)

                          In examining the key assembly I noticed that when keys are fully depressed none of the pads extend very far past the bottom of the keys' plastic housings. Some pads don't extend very far at all. I also noticed that the aluminum/mylar of most of the pads is slightly deformed (picture "domed") due to their scrubbing against the inside of the plastic housings due to a very slight slant in the pad stack. The aluminum/mylar "dome" stays intact and may even accentuate as a key is depressed until it's fully extended, at which point it begins to flatten out due to pressure against the PCB pads. I'm wondering if this "dome" effect in combination with the limited pad travel might be contributing to the problem: as a key is depressed and the domed mylar approaches the PCB pad site the sensed capacitance doesn't "jump" to provide a solid key detection, maybe it ramps instead as the dome flattens. Further, if the domed mylar doesn't flatten enough due to the limited travel of the pad there may not be enough of a capacitance change to be reliably detected.

                          To test some of this madness I put one of the double-height pads in a key that previously wasn't working at all. The pad now extended past the plastic housing further than I would have liked but there was no dome and suddenly that key started working pretty well. Hm.

                          So my wonderings at this point are A) pads for a Sol need to be somewhat thicker, maybe somewhere in between a normal and a double-height pad and B) the "dome" effect has to be somehow minimized by reducing/eliminating any slant the pad stack might have so a pad doesn't scrub against the sides of its key housing.

                          Dunno, just thoughts. Capacitive keyboards really do seem to be freakin' voodoo and Sol keyboards are 40-year-old freakin' voodoo. Lovely.

                          Thoughts?

                          Comment


                            #28
                            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.

                            Comment


                              #29
                              It was the 70's, baby!

                              It would be a great question for Lee, however. That keyboard was the bane of many a Sol, both kit and assembled. By the time I built mine in '78 the kits came with pre-assembled keyboards and even those were hit-or-miss. Mine had to be replaced immediately as it was DOA (but I didn't know it until I had built the whole system).

                              Comment


                                #30
                                Originally posted by DaveL View Post
                                It was the 70's, baby!

                                It would be a great question for Lee, however. That keyboard was the bane of many a Sol, both kit and assembled. By the time I built mine in '78 the kits came with pre-assembled keyboards and even those were hit-or-miss. Mine had to be replaced immediately as it was DOA (but I didn't know it until I had built the whole system).
                                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.

                                Comment

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