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Texelec's keyboard foam replacements

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    #46
    Originally posted by DaveL View Post
    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.
    yup, that's what I used!pads.jpg

    Comment


      #47
      I've built a few sets of these now - I've found 5mm podiatry foam (which is available with adhesive backing, and is, like the track bed foam, open cell) + aluminised mylar space blanket to work perfectly.

      Comment


        #48
        Sara was gracious enough to send me a set of her foam pads. While I can compare them to the ones I made, I can also compare them to an original Keytronic version that John Woodall sent me some time ago.

        By no means is this scientific but there are a couple of differences that make Sara's different.

        1. They are thinner overall. I didn't measure with a caliper but they are visually thinner. Here is a visual comparison picture:

        Pad comparison 1.jpg


        2. The foam is too dense. I used the same item (one of those Intel 4004 commemorative clocks that are quite heavy) and placed it on top of each of the pads in the same way. Here is the compression test.

        Pad comparison 2.jpg

        The foam is definitely too dense which will definitely affect key feel. Relatively, it's really hard. The thinness appears to be just enough to cause some people issues. My pads, by no means, are accurate in terms of thickness but they still works for all applications I've tried. I am certain mine will fall apart much sooner but it is a good compromise to get a more authentic feeling keyboard.

        I haven't yet looked at the metallic mylar material (I got them about 30 minutes ago) but that material feels definitely thicker than mine and the Keytronic pad. I am guessing this will be better but I wonder if the thickness and material change the capacitive properties. If I knew how to measure the capacitance, I'd be happy to do so to see if there is any difference.

        Anyway, I hope this is constructive criticism for your future pads, Sara. Your process in making them is excellent as they look very professional and straight. I really want to test out your metallic mylar material this weekend to see how it works out. It looks very durable.
        Maintainer of http://vintagecomputer.ca

        Comment


          #49
          I looks like the originals are open-cell foam, where Sarah's are closed-cell. I can't tell for certain, but it appears to look that way. A good way of testing is to hold a sheet of the stuff in front of your mouth and see if you can blow through it.
          Reach me: vcfblackhole _at_ protonmail dot com.

          Comment


            #50
            Originally posted by Chuck(G) View Post
            I looks like the originals are open-cell foam, where Sarah's are closed-cell.
            Yes, the originals are open-cell and Sarah's are closed-cell, hence the resistance when collapsing. This affects key feel as the keys are not allowed to bottom out so you don't get the full key travel. That said, it might not be a big deal to some who just need a working keyboard.
            Maintainer of http://vintagecomputer.ca

            Comment


              #51
              Ah, well. I guess Sara doesn't like us anymore. I bailed and found a Sun Type 4 for a reasonable price to scavenge for pads. I set aside a few to send to her as I still think her mylar/aluminum is better than the original design. If we could just fix her foam...

              Comment


                #52
                Has anyone tried the Woodland Scenics foam sheets to make pads? 5mm foam (3/16") sheet cut for form the pads. There pretty firm and hold their shape, worked well for me and my Visual 1050 and TRS 80 model II.
                @ BillDeg:
                Web: vintagecomputer.net
                Twitter: @billdeg
                Youtube: @billdeg
                Unauthorized Bio

                Comment


                  #53
                  Originally posted by DaveL View Post
                  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?
                  [ATTACH=CONFIG]46864[/ATTACH]

                  5mm or 3/16inch is what I found worked.
                  @ BillDeg:
                  Web: vintagecomputer.net
                  Twitter: @billdeg
                  Youtube: @billdeg
                  Unauthorized Bio

                  Comment


                    #54
                    Originally posted by billdeg View Post
                    5mm or 3/16inch is what I found worked.
                    I used 1/4" height for the pads as that was all I could find. Hence, why mine are a little taller but they still work too.
                    Maintainer of http://vintagecomputer.ca

                    Comment


                      #55
                      Originally posted by billdeg View Post
                      Has anyone tried the Woodland Scenics foam sheets to make pads?
                      Yes that is what I used. I've mentioned that along with pictures. The material is a bit too dense, but they work fine.
                      I did a search again for 5mm polyethelene open cell foam, but couldn't find any less than 1/2" thick. Polyurethane
                      is what is in the 5mm sheets that are around.

                      I just ordered some of this to try
                      https://www.ebay.com/itm/5mm-10-76sq...M/132190055705

                      Aluminized on one side, glue on the other for the plastic disc. It is probably closed cell so it's going to be dense.

                      Comment


                        #56
                        Does anyone think that this stuff might work? It comes in 1/4" thickness.
                        Reach me: vcfblackhole _at_ protonmail dot com.

                        Comment


                          #57
                          Originally posted by falter View Post
                          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. ...trackbed.
                          Originally posted by Al Kossow View Post
                          yup, that's what I used
                          Originally posted by drdanj View Post
                          I've built a few sets of these now - I've found 5mm podiatry foam (which is available with adhesive backing, and is, like the track bed foam, open cell) + aluminised mylar space blanket to work perfectly.
                          Originally posted by snuci View Post
                          Sara was gracious enough to send me a set of her foam pads. While I can compare them to the ones I made, I can also compare them to an original Keytronic version that John Woodall sent me some time ago…
                          Anyway, I hope this is constructive criticism for your future pads, Sara. Your process in making them is excellent as they look very professional and straight. I really want to test out your metallic mylar material this weekend to see how it works out. It looks very durable.
                          Originally posted by Chuck(G) View Post
                          I looks like the originals are open-cell foam, where Sarah's are closed-cell. I can't tell for certain, but it appears to look that way. A good way of testing is to hold a sheet of the stuff in front of your mouth and see if you can blow through it.
                          Originally posted by snuci View Post
                          Yes, the originals are open-cell and Sarah's are closed-cell, hence the resistance when collapsing. This affects key feel as the keys are not allowed to bottom out so you don't get the full key travel. That said, it might not be a big deal to some who just need a working keyboard.
                          Originally posted by billdeg View Post
                          Has anyone tried the Woodland Scenics foam sheets to make pads? 5mm foam (3/16") sheet cut for form the pads. There pretty firm and hold their shape, worked well for me and my Visual 1050 and TRS 80 model II.
                          Originally posted by DaveL View Post
                          Ah, well. I guess Sara doesn't like us anymore. I bailed and found a Sun Type 4 for a reasonable price to scavenge for pads. I set aside a few to send to her as I still think her mylar/aluminum is better than the original design. If we could just fix her foam...
                          Hello kind gentlemen!

                          OH NO DavidL, please don’t give up on me! I do still <3 love <3 all of you and I greatly appreciate the hard work in testing my pads by all of you and I appreciate the in-depth feedback, greatly. I just saw the posts yesterday, I have been super busy the last few days so I was a bit slow on checking back. I just saw the subscribe to thread option too.

                          When I did see the posts I also got a little obsessed because the forum was not loading correctly across 4 different browsers. The stylesheet is not loading so reading through the forum in straight HTML without the stylesheet is a little cumbersome. It’s loading in Edge now, so here I am. Anyone having this issue in Firefox? I can’t seem to fix it, cleared cache and cookies and my browser is up to date. Sorry got off topic there.

                          Anyway, all that said I am reading through and am now on the hunt for new foam. I saw billdeg was using Track-bed about a week or so ago on his website so I was already considering this. I have been digging over here. Now I am contemplating height and hoping to find out exactly what that foam is made of as I would like to buy it in larger sizes, preferably by the roll and not a 1 ĺ” wide roll. I know it’s open-cell and according to the Track-bed site it will not quickly deteriorate, however that promotional video appears to be relatively dated. At least that means it shouldn’t be going away anytime soon, right? I’m not ruling it out as I can at least buy it by the sheet.

                          I will need testers guys, so please don’t give up on me guys!

                          OK, checking my private messages now.

                          Comment


                            #58
                            Originally posted by snuci View Post
                            [ATTACH=CONFIG]46921[/ATTACH]
                            [ATTACH=CONFIG]46922[/ATTACH]
                            Originally posted by Chuck(G) View Post
                            Does anyone think that this stuff might work? It comes in 1/4" thickness.
                            Originally posted by billdeg View Post
                            Has anyone tried the Woodland Scenics foam sheets to make pads? 5mm foam (3/16") sheet cut for form the pads. There pretty firm and hold their shape, worked well for me and my Visual 1050 and TRS 80 model II.
                            Originally posted by Al Kossow View Post
                            yup, that's what I used![ATTACH=CONFIG]46894[/ATTACH]
                            Chuck(G), this link has been SUPER helpful, THANK YOU for posting this! I think I have figured out that the speaker/filter foam is not what we need. I think 30ppi would be a filter used in A/C units and window units and possibly even wet/dry vacuums and fish tanks just with a thicker, more stout, plastic. I am looking into though. However, this site is showing me a ton of specs and I am learning a lot about what I need to look for in my research. So thank you very much! I think I'm getting very close.

                            Everyone else, not just the people I quoted, I quoted for reference purposes. My future pads will likely be thicker, like Snuci’s pads. I’m wondering if I missed something in all the responses, did anyone else address the double height pad question Snuci asked before about the Lisa? I’m starting think that was only necessary for the mechanical caps lock key because my pads were too thin before. This is assisting me in leaning more toward 1/4” instead of 3/16” (5mm). However, ľ” may be necessary due to availability as it seems to be an issue when it comes to 3/16”. However, I don’t think it will be a problem using 1/4", I suppose we’ll see. Please feel free to share your thoughts on that.

                            I just requested some samples, I do have some original pads from my Compaq that I will be using for comparison. This company has responded quickly so I’m hoping the samples will arrive quickly as well. Since I am changing foam I am going to try to get as close to the original foam as possible!

                            Thanks again for your help, ALL OF YOU! I truly do appreciate the feedback and critiques. I need it to make accomplish the best results. I’ll keep you all posted on my progress.

                            Comment


                              #59
                              Originally posted by sarawill View Post
                              My future pads will likely be thicker, like Snuciís pads. Iím wondering if I missed something in all the responses, did anyone else address the double height pad question Snuci asked before about the Lisa? Iím starting think that was only necessary for the mechanical caps lock key because my pads were too thin before.
                              Hi sara,

                              I took some pictures of a Lisa keyboard I haven't replaced the pads on yet. The pads in it were essentially "dust". The Caps Lock is not double height and i haven't needed to use anything but the 1/4" pads I have made in my refurbished keyboards. I also put one of my pads in and took picture of before and after locking to show the height. I will post these pics later for reference.

                              I know you told me not to but I'm going to send you some of my pads anyway. I only needed to look at one of your pads to determine it's construction. it will help you assess my foam and thickness, at the very least.
                              Maintainer of http://vintagecomputer.ca

                              Comment


                                #60
                                Originally posted by snuci View Post
                                Hi sara,

                                I took some pictures of a Lisa keyboard I haven't replaced the pads on yet. The pads in it were essentially "dust". The Caps Lock is not double height and i haven't needed to use anything but the 1/4" pads I have made in my refurbished keyboards. I also put one of my pads in and took picture of before and after locking to show the height. I will post these pics later for reference.

                                I know you told me not to but I'm going to send you some of my pads anyway. I only needed to look at one of your pads to determine it's construction. it will help you assess my foam and thickness, at the very least.
                                I truly appreciate that, I just hated to cost you any money or waste more of your time. I'm happy to cover the shipping! Since you are sending one of yours maybe you could include an original green one too? My originals from the Compaq are charcoal in color, not green. I don't know if that makes any difference but I'd like to feel it if possible and compare to the samples I'm getting. I know you showed an image compressed before with all three for comparison, but it's hard to "see" the difference.

                                Let me know if you need my address.

                                Comment

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