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Texelec's keyboard foam replacements

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    #91
    Originally posted by SpidersWeb View Post
    I am looking forward to hearing more about the new foam and would be keen to order when available.

    I just redid the pads in a Wang Professional keyboard (same as Wang 723 keyboard I think, but with different electronics), and it's a wee bit of a slow/squishy typing feel - so I'd be very keen on pads that'll collapse easier. I wouldn't really want to type on it like that for a long period of time.

    One other tiny detail I'd like to mention would be if it's possible to get a few more in each bag - my Wang keyboard had more than 98 keys.

    Having someone who will supply them precut with mylar is a godsend. I couldn't do that by hand without going insane.
    So thank you very much for your efforts Sara! (and everyone else that's helped with ideas/feedback).
    I just listed them for sale. The list of people waiting was starting to really pile up, I just couldn't wait any longer. I have included 105 per bag, I think I had a couple people tell me they needed a few more so I felt 105 seemed like a nice round number. The price is still the same as it's always been.
    TexElec-Blog-Post-9.12.2018-Featured-Image.jpg

    Here is the listing:
    https://texelec.com/product/foam-cap...ads-keytronic/

    Comment


      #92
      I finally had an opportunity to work with the foam pad set I ordered on eBay on Sep 27, 2018 for my Compaq Portable. Before starting the replacement, the keyboard basically had about 1/3 of the keys not working. After replacing the pads with the new ones, I kept getting "stuck key" symptoms, even after some advice from another to make sure I got the mounting plastic disc under all four tabs in the key caps. Still the same stuck key symptoms. That same person told me the pads may be too tall for the Compaq keyboard and that's why I'm getting a stuck key. I even made sure that I see no mylar surfaces sticking out of the key cap well after the pads are inserted. There appears to be less than 1/8 inch difference between the square key cap frame surface and the recessed mylar surface on the foam inserts. Does that make the gap too shallow? Could gravity simply be allowing the foam to stretch just enough to cause surface contact with the circuit board? I have verified that the space bar is at least one of the stuck keys, no matter how many times I reinsert or replace the foam insert for the space key, as the cursor moves one space at a time when DOS prompts me for a new time and date.

      Someday I'll be able to find a block of time to revisit the issue. It was just a bit disappointing to go through all this and having these issues.

      Comment


        #93
        Originally posted by VintageVolts View Post
        I finally had an opportunity to work with the foam pad set I ordered on eBay on Sep 27, 2018 for my Compaq Portable. Before starting the replacement, the keyboard basically had about 1/3 of the keys not working. After replacing the pads with the new ones, I kept getting "stuck key" symptoms, even after some advice from another to make sure I got the mounting plastic disc under all four tabs in the key caps. Still the same stuck key symptoms. That same person told me the pads may be too tall for the Compaq keyboard and that's why I'm getting a stuck key. I even made sure that I see no mylar surfaces sticking out of the key cap well after the pads are inserted. There appears to be less than 1/8 inch difference between the square key cap frame surface and the recessed mylar surface on the foam inserts. Does that make the gap too shallow? Could gravity simply be allowing the foam to stretch just enough to cause surface contact with the circuit board? I have verified that the space bar is at least one of the stuck keys, no matter how many times I reinsert or replace the foam insert for the space key, as the cursor moves one space at a time when DOS prompts me for a new time and date.

        Someday I'll be able to find a block of time to revisit the issue. It was just a bit disappointing to go through all this and having these issues.
        I am so sorry for the struggles you’re having! I know it can be a finicky process and doubt in the replacement pads does not help. I would like to send you another bag with shorter pads. The pads do vary in size a bit due to the nature of the open cell foam so I can get a bag of shorter pads for you to try if you would like. If so, please send me a message with your eBay name and actual name so I can find your old order. I will get a set out to you right away.

        I also thought I would add updates as to what has happened with the testing and so forth. I am going to make it as short as I can as I plan to add much more detail in a blog post on our website. We have spoken to KeyTronic at this point as well as one of their original manufacturers so I thought the vintage computer community would appreciate the knowledge. I will likely wait until one more thing I discuss below is finished.

        Since the testing on this thread fizzled, I have managed to get my hands on some old terminals that were stored in an airplane hangar for years. Needless to say, they were all a mess, so they are prime for testing. All I have done to the PCB in my terminal is cleaned it with a bit of rubbing alcohol, no eraser applied! So now I can test on my old terminal and a my, all too reliable, Compaq Portable. I have also had many people purchase pads and come back with success stories and even get more pads for other machines. I have also had someone use them on a BTC keyboard.

        That being said, I have also had a handful of people have issues. With the exception of one other customer, the problem has been with some keys not registering a reading on key press. In some cases, this was remedied by cleaning the PCB pad repeatedly. I don’t always hear the end results so I don’t know what happened with everyone. These few issues have triggered me to keep trying, as you all know, I don’t want to give up on these pads! While I tried doubling up the foil side, we decided to give contacting KeyTronic another try. Yes, we had tried long ago to no avail. My testing led me to determine I needed thinner aluminum plated mylar which has now been verified by an analysis of the original pads by a metalizing company! In fact, my original aluminum plated mylar thickness was correct only it is 1mil “sandwiched”, not a single layer of 2mil.

        I have had one other customer contact me, it was just about a week ago actually, with a similar height issue and it was on a Compaq. Note, I am not having this issue on my Compaq. Like I said, my Compaq is too reliable. This customer decided to make shims with a 3D printer instead of getting another bag from me. It is possible you both received an extra tall batch. But I’m not really satisfied with this outcome, so we decided to try another foam manufacturer to see about getting foam custom cut elsewhere. It just so happens that the manufacturer we called knows a guy with a special machine and now I have a sample on the way right now!

        Comment


          #94
          Sara,
          Im amazed this is still a problem. I remember last year the first batch I had from you had a 60% failure rate but you promptly sent a replacement which was 100% effective for my compaq portable. I'd still buy your product in a heartbeat as it did the job perfectly. I am wondering if the problem is everyone with Compaq portable isnt using a small flat blade screw driver to ensure all 4 corners of each backing bad are pressed into the retainer, its time consuming but not difficult.

          Comment


            #95
            Originally posted by VERAULT View Post
            Sara,
            Im amazed this is still a problem. I remember last year the first batch I had from you had a 60% failure rate but you promptly sent a replacement which was 100% effective for my compaq portable. I'd still buy your product in a heartbeat as it did the job perfectly. I am wondering if the problem is everyone with Compaq portable isnt using a small flat blade screw driver to ensure all 4 corners of each backing bad are pressed into the retainer, its time consuming but not difficult.
            The good news is that it has really been just a handful of people. Because of these issues I am making them even better and reaching KeyTronic was pretty cool as well!

            Comment


              #96
              Originally posted by sarawill View Post
              The good news is that it has really been just a handful of people. Because of these issues I am making them even better and reaching KeyTronic was pretty cool as well!
              Hi, I bought some of your pads. I thought you did a very nice job making them and I am grateful for your efforts. However, they do not work well for the keytronics keyboard in the Sol-20 (they probably do in other types of keyboard) I found out the reason why. Here is some text from an article I wrote about fixing the keyboard:

              4) The keyboard required the usual replacements of the foam pads with the dielectric
              coated discs.
              The original arrangement uses a 0.07mm thick dielectric (possibly mylar or polyester)
              on a foam disc with the conductive layer sandwiched in the middle of the dielectric, so
              about 0.035mm from the surface.
              Experiments showed that the capacitance has to rise to about 10 to 15pF to produce a
              reliable negative going output pulse from the transistorized differentiator and threshold
              circuit, of about 800nS width. This sets the S-R flip flop U14 on a key-press.
              Prior to getting the Sun 4 keyboard replacements pads, I had experimented with
              conductive rubber discs, which also work and running in a “DC coupled” mode the
              output pulses are 5uS long.
              I bought some other capacitance pads to try which had a similar thickness dielectric, but
              the conductive coat was on one surface and therefore the capacitance didn’t rise high
              enough for reliable key detection as the dielectric layer was too thick.

              ......So if you can find a material where the conductive layer is only about 0.035 from the surface, they would also be fine for the Keytronics/Sol-20 keyboard.

              Comment


                #97
                Originally posted by Hugo Holden View Post
                Hi, I bought some of your pads. I thought you did a very nice job making them and I am grateful for your efforts. However, they do not work well for the keytronics keyboard in the Sol-20 (they probably do in other types of keyboard) I found out the reason why. Here is some text from an article I wrote about fixing the keyboard:

                4) The keyboard required the usual replacements of the foam pads with the dielectric
                coated discs.
                The original arrangement uses a 0.07mm thick dielectric (possibly mylar or polyester)
                on a foam disc with the conductive layer sandwiched in the middle of the dielectric, so
                about 0.035mm from the surface.
                Experiments showed that the capacitance has to rise to about 10 to 15pF to produce a
                reliable negative going output pulse from the transistorized differentiator and threshold
                circuit, of about 800nS width. This sets the S-R flip flop U14 on a key-press.
                Prior to getting the Sun 4 keyboard replacements pads, I had experimented with
                conductive rubber discs, which also work and running in a “DC coupled” mode the
                output pulses are 5uS long.
                I bought some other capacitance pads to try which had a similar thickness dielectric, but
                the conductive coat was on one surface and therefore the capacitance didn’t rise high
                enough for reliable key detection as the dielectric layer was too thick.

                ......So if you can find a material where the conductive layer is only about 0.035 from the surface, they would also be fine for the Keytronics/Sol-20 keyboard.
                I’m so sorry the pads didn’t work out for you. Thank you for the information, I appreciate it!

                You are correct, the discs are in fact aluminum plated mylar. The metallizing company did an analysis of some working original pads for me and found they were made from 2 layers of 1mil (0.0254mm) mylar with the aluminum plating in the middle (sandwiched). The only difference between mine and the original is that mine have around 30% to 40% more metal. However, he was certain that was due to the deterioration of the original pad over the years. He felt as if I was using the correct material. That thickness leads me to think that these new ones I have will work for you. I have tested them on my old dirty Visual Model 50 terminal with great success.

                I would really like to send you another set of pads, I have already pulled up your order so I already have your address ready. Would like another set of pads with the new dielectric? I would greatly appreciate feedback on their operation in a Sol-20.

                Comment


                  #98
                  Hi Sara,

                  That is a nice offer for more pads, you are very helpful & kind. Now I have the keyboard working it is unlikely I will dismantle it again in the near future, so I'm ok for them for now.

                  It sounds as though you have really figured these pads out. I'd expect your new ones would be fine for practically any capacitance pad keyboard now. The design of the keyboard in the SOL-20 at least, seems to rely on a very thin dielectric layer to get the capacitance high enough to be detected. It is quite an interesting circuit they use to do that.

                  Even though I had those issues with the pads I got from you, I was still very impressed with them and the effort you went to, to manufacture them. The vintage computing community needs these kinds of replica parts or it will not be possible to fix a lot of computer equipment in the future. Your efforts are much appreciated.

                  Hugo.

                  Comment


                    #99
                    Eagle 105 Enahnced Keyboard.jpg
                    Just used a set of these pads to restore my Eagle 105 Enhanced Keyboard, used on Eagle 1600 and Eagle PC machines. So far all the keys that DOS recognizes work fine. Now If I had that elusive "Test and Initialization Diskette", it might have tools to test everything.

                    When I first got this keyboard it looked like it had hardly been touched. Probably some Eagle user swapped theirs for a normal keyboard. Of course, now it has the usual signs of use on it. Only other thing I probably need to worry about is that the connector cable's plastic insulation is very dry and might start cracking.

                    As mentioned above, these foam pads are now sold via their web store: https://texelec.com/product/foam-cap...ads-keytronic/ (I tend to get eBeh tunnel vision sometimes)

                    Comment


                      Just to say I replaced all the pads on my Compaq Portable with the Tex-elec pads and it now works perfectly. About 40-50% of them were bad before. Really valuable parts - thanks for offering them for sale!!

                      As Verault says, it's critical to ensure all 4 fingers are correctly clicked into place over the backing disk. Took me a while to figure out how to do this - used a scalpel in the end and double checked them visually before reassembling the keyboard.

                      Comment


                        Just finished replacing pads on my Compaq Portable Plus with ones from Tex-Elec and the keyboard works great.

                        Ditto on the importance of getting all 4 fingers onto the backing disk. My tool of choice for getting them on is a pair of very small, curved, surgical scissors, which are very efficient for poking them into place. I also took Muzzer's advice about double-checking before I put the keyboard back together.

                        Comment


                          I was very happy to find these foam pads pre-made for such a reasonable price.

                          I replaced all the pads on my Compaq Portable and all keys are working on the first try.

                          I slid each pad onto the key which typically seated 2 of the clips (fingers). I then used a dental pick for the remaining two clips.

                          Comment


                            Originally posted by Hugo Holden View Post

                            Hi, I bought some of your pads. I thought you did a very nice job making them and I am grateful for your efforts. However, they do not work well for the keytronics keyboard in the Sol-20 (they probably do in other types of keyboard) I found out the reason why. Here is some text from an article I wrote about fixing the keyboard:

                            4) The keyboard required the usual replacements of the foam pads with the dielectric
                            coated discs.
                            The original arrangement uses a 0.07mm thick dielectric (possibly mylar or polyester)
                            on a foam disc with the conductive layer sandwiched in the middle of the dielectric, so
                            about 0.035mm from the surface.
                            Experiments showed that the capacitance has to rise to about 10 to 15pF to produce a
                            reliable negative going output pulse from the transistorized differentiator and threshold
                            circuit, of about 800nS width. This sets the S-R flip flop U14 on a key-press.
                            Prior to getting the Sun 4 keyboard replacements pads, I had experimented with
                            conductive rubber discs, which also work and running in a DC coupled mode the
                            output pulses are 5uS long.
                            I bought some other capacitance pads to try which had a similar thickness dielectric, but
                            the conductive coat was on one surface and therefore the capacitance didnt rise high
                            enough for reliable key detection as the dielectric layer was too thick.

                            ......So if you can find a material where the conductive layer is only about 0.035 from the surface, they would also be fine for the Keytronics/Sol-20 keyboard.
                            Just saw this post of your. Live and learn. May have to try something else - another approach.

                            Rick

                            Comment

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