 Well, I am not having a lot of luck with my keyboards recently. Not only had my Amiga keyboard failed due to membrane failure, there'll be a video about that coming out shortly, but my ZX81 keyboard has also failed due to membrane failure. This is pretty normal with these old computers. The membranes are made out of pretty brittle plastic which gets more and more brittle as time passes. Luckily, you can get replacements. And this is a replacement keyboard for the ZX81. This tail plugs into the motherboard. This is a self-adhesive keyboard thing that sticks on this part of the case. So I am going to replace the keyboard of this ZX81, but first I will demonstrate what's wrong with it. The keyboard is running and you are seeing a screen capture of it. Most of the keys still work, except you notice that 5 and 6 have failed, T and Y have failed, G and H, B and V. C and N work, F and J work, R and U work and 4 and 7 work, so it's just these set here. This is a classic symptom of a cracked trace in the membrane. The way these keyboards work is they divide the keyboard into rows and columns. You can in fact see with this that there are two cables here, one which connects to the top of the keyboard membrane, the other which connects to the bottom. When you press one of these buttons it touches the two together. So one of these traces will have failed. It's probably repairable if I had some conductive paint, but I can't be bothered so I'm just going to put a new one in. Repairing them is a fool's game anyway because once they go they just go. So let's take the lid off this thing. So luckily the ZX81 is pretty simple to dismantle if I can find an appropriate screwdriver, not that one. This thing was made as cheaply as humanly possible. It's not quite as cheap as the ZX80 which was made out of vacuum formed plastic and was, well, the keyboard was actually part of the PCB. The PCB poked out through a hole in the front of the case which was fairly special. So this thing should open up and this shows you the PCB, the composite mod I did so that I don't need a RF modulator and the really rather handsome old fashioned red PCB. I need to take the PCB off. Okay now that screwdriver is not big enough. Okay and that is the top side of the PCB with the processor, the custom chip that does most of the work of generating the video. We've got the RAM and this will be the ROM. This is the now defunct RF modulator with a cable connecting it to the composite mod. So the output of this is producing composite video rather than RF video. I didn't bother taking the RF modulator off because it's got this socket as part of it and besides taking it off is hard. So the keyboard tails pull out, that just broke right off. Yes, this keyboard is not going to work anymore. I just need to get this out. There we go. All right, annoyingly the composite mod doesn't actually mount anywhere useful so I just had to stick it on. So I'm going to have to put it off. What did this wire connect to? Nothing as far as I can tell. There are a few configurations for this. You can see by the unpopulated pounds on that side of the board. Yeah I think that's unused hopefully. Anyway this can now go aside and we start with the interesting bit. We have to get this keyboard off and it is stuck on. So for this I'm going to need to get out the hot air gun. Okay now as I say this thing is stuck on so it could just be pried up but it works so much better if you heat it up first. So I'm trying to arrange my hands. Let's see how this works. It's set to the minimum temperature. I haven't actually done this before. Yes, this appears to be working pretty well. So we just insert the prior under this thing. I should probably have used the bigger nozzle. The instructions recommend a hairdryer but I don't actually have one. The hot air gun should do fine. The tails for the keyboard go through the case for a slot here which is why that bit won't lift up. I need to take the rest of this thing off. Yeah this is really annoying. I need to use multiple hands. So I've got one hand holding the hot air gun which also has to rest on the case to hold it down and then the other hand has to peel the thing off. But it is coming. I suspect the ancient adhesive probably isn't much good anymore. The air gun is set for its minimum temperature which is 100. I wonder if I'll be worth. Yeah I could crank it up but I don't think it's worth it. This is actually working. And as you might imagine I really don't think this keyboard is going to be any use after it's taken off. I mean it's broken anyway. This is not as delicate as I was hoping it was going to be. And I don't know what's this. Oh ho, that's the keyboard. And this is the sticky layer that was holding it on. So let's see if we can peel this off. Yeah this thing's revolting. I was afraid I was going to have to scrub this thing with IPA but this is working out nicely. But it's come loose. All right, good. Now it's done. I just need to put the, come on. The wand goes into the heat guard at a particular angle to turn it off. There's a magnet that throws a reed switch. There we go. But it's not really particularly obvious how it goes. Okay, so here we have the case. It's a little bit sticky but that's fine. Here is the old membrane. The torn brittle plastic. You can see there are two layers. This is the, these are the actual contacts themselves that get pressed together. I peel this apart. There we go. See the top and the bottom, these are, this is not very conductive material. It's a terrible, terrible keyboard. The only thing going for it is that it was incredibly cheap. And here is the replacement. This is new construction. Well, it says copyright 2014. Membrane keyboards of this kind are still used today for things like ATMs and cheap machinery. These do have the advantage in that they're waterproof and easy to clean. So all that we need to do is to stick the tail through there and then stick this thing down. Now interestingly, the new keyboard is quite a lot thicker than the old one. I don't want it to stick down yet. There we go. There's still some adhesive on the tray. Parts of that will be the the paper backing that I have to peel off, but okay. So I'm going to get one try at this. I can peel the blasted stuff off. I don't want to damage the keyboard itself. Oh, come on. Here you go. So this reveals the keyboard layers, which is subtly different. It is a new design rather than a reproduction of the old. Hopefully this should last longer. So this goes in here. Okay, that looks good. Let me just press it into place and we're done. Keyboard replaced. We now have to reassemble everything and see if it still works. So if you're out, how it all goes together now. The PCB goes in like this, but the keyboard membrane plugs in here. Just trying to think what the best way to do this is. Probably this way. The PCB will then screw onto the top. Yes, I should have taken better notes as to how it goes together. So it will actually go together like this. So if you plug the keyboard in, the tails just push into the connectors. It's really a bit dubious and difficult to see. Here we go, like so. Then the PCB will go down like this and these two screws will go in. So one here and one here, right. We then stick the composite mod board down. So the black wire is unused. We can reuse the old piece for adhesive and then this should just push down here and then the bottom goes on and that should be it. Okay, doing up the screws. We've got the short ones that go in the front and you have to be careful because Sinclair's cheap and nasty plastic continues to be cheap and nasty 40 years on. And in fact, it's probably even cheaper and nastier and if you're too rough with the screws, you will break the plastic. I don't wanna do that and that should be it. So let's hook up the video again and plug in the power and see what happens. Well, it boots. One, two, three, four, five, six, seven, eight, nine, zero. Q, W, E, R, T, R, U, I, I, O, P. E, V, B, N, M, dot, space. Write all the keys work. Close quote, new line. 20, go to 10. Fantastic. Yes, there is no repeat key. So in order to get all the way to the right-hand end of the line, you have to do this. Takes forever. Okay, so let's add a semi-colon, which is here. Fantastic, works fine. That, well, it'd be wrong to say that that couldn't have been simpler, but that was pretty simple and so much less work than the Omega membrane replacement is turning out to be. So that is a nice success. I will discard this copyright 1980. This one is 2014. The, you can see that the colors of the new one are slightly brighter, but it's a pretty decent replacement. Some of the styling, you can see that the line around the box, for the air graphics character is a little bit thicker on the new one. Yeah, and the shape of the dollar sign is subtly different, but there's very little to it. They've done a really nice job of replacing this thing. So, fantastic. I now have a fully functioning ZX81, which I can use for ZX81 things. Anyway, I am glad that this video has actually turned out to be as short as I hoped it was going to be. I hope you enjoyed this video. Please let me know what you think in the comments.