 I have a new parcel. This has just arrived via eBay from London. Hopefully it contains replacement parts for my plotter, which has shown up on the channel before. I managed to bodge the plotter back into working order after discovering that the stepper motor bearings were fried. And this should contain a, for parts only, plotter module for the same plotter. Hopefully I will be able to extract the spare parts I need to fix it from this. So let's open it up and see what it looks like. This is actually a little bit odd. I was talking to the seller about postage to Switzerland when suddenly they said they weren't going to charge me and sent it to me for free, which is a little bit surprising. I mean, the postage is not inconsiderable, but thanks very much and Merry Christmas. So, ow! I avoid trying to cut myself. What have we got here? We have a extremely manky plotter and a bunch of paperwork, which I shall get out of the way so that I don't have to pixelate it. So this is the shell of the plotter. It's got the plotter module inside. It looks like the bits are all there. This is a different model to mine. Just looking at mine. Mine does not have this silver plastic. It's white beige, but it is still the TRS80CGP115. Oh, wow! Serial number 1782. Well, I shall... Actually, I am just wondering whether to try and power this up and see if it works or to take the lid off first. Let's power it up, I think. Oh, hang on. There's a pen in it. There's a full load of pens in it, that's nice. These pens are incredibly hard to find. So, okay, that's not moving. So the failure modes for these plotters are typically that the nasty nylon gears fail. These are friction fit gears that go on the end of the stepper motor axles and they shrink over time and eventually they crack and jam. And that feels jammed. I'm not particularly bothered about that because I only really want stepper motors, but if the entire module works, I can just replace the one in my printer with this one. But it looks like it's not. Okay, let's get some power and see what this does when I turn it on. Okay, here it is. I've put a roll of paper in it. This is something I drew on the other printer. It's a classic piece of vector art from Techtronics. And you notice that it's all kind of mangled. This is because the other printer would occasionally miss steps and nothing lined up properly. And this is the fault that I'm trying to fix. So I've got a power cable from the other printer. I think that's off. Plug it in. Turn this on. This is actually trying to draw something on the roller. Yep, that is broken. Put the paper in. I actually also found another pen in the case. The paperwork seems to come from the original seller. This plotter came imported from the US. So it's possible that my seller wanted a working one and when it discovered that it wasn't working, sold it off on eBay to me. Which is fine. Feeding paper in is a little bit tricky. Okay, so let's try the self-test. Well, the pen has failed. Yeah, this is supposed to be drawing text, but the head isn't moving. That grating noise is bouncing against the end stops. So I am going to guess that the nylon bearings have died. Hopefully it's not the stepper motor. All right, let's open her up and see what there is to see. The main thing I'm seeing is a lack of screws holding it together. The case is quite beaten up. It's got these nasty plastic clips, which I'm not sure the other one had. There you go. Yeah, this has been opened up. We go and it's the same as the other one. So if you've watched that video, you'll see all this. This one goes round. This one does not. I'm going to mark the... I'll attempt to mark the... I need a felt pen for that. I'll attempt to mark the roller so that I can tell what the... how many times it goes round. So let's put a green mark there. That's actually going around more than once. That suggests that the nylon bearing has not failed. This looks to be in considerably worse condition than mine. So what could be jamming? So it's maybe a quarter of a turn of this one and it's one rotation of the internal gear here. So it's incredibly grubby. I wonder if there might just be grit in the teeth. So I'm probably, I guess, going to have to remove and replace the stepper motors. I have actually managed to get the stepper motors out of the other plotter. So I do know approximately how to do it, but it's a really annoying dismantling process. There's a lot of stuff that's friction fit and just very tight. Okay, well that hasn't done anything. So other things it could be, there's the head moves on this wire belt. As you can see here, it goes around a couple of pulleys. So the pulleys could have failed. They're quite tight, so that seems strangely flexible. The belt is tensioned by this spring and I'm wondering if I can unhook it or whether that's even a good idea. Let me try and get the spring out so I can see it. Yes, it does hook onto a loop at one end. I have a feeling that, I'm doing that's a really bad idea. Or I could just push hard. Well, I know it's not the fault of the stepper motor because otherwise it would be failing at a single revolution of this little gear. So it must be something to do with this. There is some gunk in the thread. Let's get something finer. Oh my God, piece of grit. That's improved things a lot. I have a feeling that the problem here is just that it's filthy. Now it's wedged in two positions. I'll play with this for a little bit but then I think I just need to bite the bullet and remove the stepper motors. I don't think that's going anywhere. Let's just remove this. The other one is in much better condition anyway. So I will attempt to put the stepper motors from this module into the other one which will then give me a almost mint in the box plotter. Although I have done a fair bit of work on the other one which turned out to be unnecessary eventually replacing part of the power supply. So the plotter module is fastened in by two bolts. So I'm going to need to immobilise the bolts at this end while undoing the screws. Really get a small set of spanners. Now I need to do the other side. If you're lucky the nut rather will have wedged and make it easy to remove which I think it has. No it hasn't. Sorry this isn't much to look at due to size and focus issues. Alright this just moves and I can get the... Here is the focus. It's just a mangled mess. So that's the way. Alright so here is the plotter module itself. It's an off the shelf thing. They were used in a whole bunch of different plotters of which this was one. They are cheap and cheerful and pretty lightweight. So in order to get at the motors I need to remove this uppercase here which just unclips more or less and is fastened in in a slightly odd way which I can't remember how I'm supposed to get it out. It's just cosmetic. It doesn't actually do anything. Ah yes there's a little spring clip there thing. And that exposes the stepper motors. So now I have a bit of a better look. Just looking at these nylon bolts. Nuts, gears, nylon gears. I think they're alright which will be nice as removing them is probably going to be a complete pain. So I wonder if the problem is... Well the problem must be these little ones here anyway. Next stage is to remove the stepper motors. The stepper motors are also bizarre friction fit things which are spectacularly difficult to get out. So first I have to undo this screw which is behind the piece of the mechanism and which is very much wedged. That was me knocking part of my microphone setup off. Okay that's not working. I don't think I've got anything else small enough for this. I wonder about a flat head. I have a very small flat headed quarter inch bit. Do. So this one I actually do have to get out. It's... I have to remove it in order to get the motor out. It doesn't have to go back in again although it would help but it does need to come out. I'm just trying to think of what I could do here. I think some penetrating oil is probably called for. Okay good old fashioned WD-40. I just want a tiny amount. Let's attempt to do this on camera shall we? Just need a tiny amount. That wasn't a tiny amount. Okay so I will then leave it for 10 minutes and come back and have another go. Okay that's been 15-20 minutes so let's have another go and see if this screw will shift. No, no it's not. Okay I need a screwdriver with some more torque to it. Okay here's one that will fit. The problem is the space is quite limited so trying to get in there is hard. I might have to remove those gears which I don't want to do. Yeah it's not quite working. Okay let us attempt to remove the gears. There's a couple of retaining clips. There's one so that slides off. Yuck and then this is a friction fit. This one's split. Can't quite see it but I can stick my fingernail in. Okay of course this is the side that seems to be working so that could have been harmless. Okay there we go. So that unscrews and now this is clipped in in a bizarre sort of way and just pops out like that. Unwind the cables and I will need to desolder these in a moment. Alright now let's try this side. Actually before I do that let's put these back on again so I don't lose them. That goes on there. That goes on there. That goes on here. It does go on here by honest. I mean it came off it should go back on again. Mixed so and kept. Alright now for this side the same thing applies except this particular lever arm is even more awkward. So can I get this in? Let's try one of the small screwdrivers first to see if that will help. Okay I'm going to have to remove this spring clip. Actually this is how you do it. Yes that just falls off. Okay so this then comes out but it's still fastened on by that belt so it doesn't come off completely. Now can I think I can bend this out of the way using one of my several hands. That's not working either. I wonder if this is going to have to come off. Well this is the pulley from this side of the belt which has come loose. So that will clip back on again in here. I was just going to check to see if this went round. Yeah that's fine. Nothing wrong there. It's not in great shape to be honest and in fact I've done that wrong because that needs to come to this side of the cable. So the cable can go over there. Okay and now I need to still need to get this screw on done. There we go. Okay so now the motor pops out the same way. Now I need to get the screw out completely but it's retained because it's stuck on the arm. So that comes out like that. Now the motor should just pop out. Come on. Okay this is kind of a mess but the next thing I want to do is to power the thing up with the motors removed to make sure the motors go round and that there's lots of torque. So this shouldn't be too tricky. This one's turning. I think there's a decent amount of torque there but I can't stop it from vibrating with my fingers. I thought I would get more than that. I don't know. Okay so now I need to remove these from the board. They will just unsolder. Each of them is fastened by a bunch of wires. I think both motors are identical. So it's important to remember what colour the wires are which is one reason why I'm doing all this on video but I shall go away and take a manual photo anyway on my phone. Okay I lost some video there. I don't know whether that was the camera turning itself off but I have now finished with this so I can put this aside unless I want to remove the logic board because I know the logic board is probably fully functional. It's easy enough to take off again if I need it. So let's put this incredibly manky thing aside. A little bit of tidying and now we're going to start disassembling my nice one. This is going to be a little bit more fraught as I don't want to break the nice one. Okay here it is. A little bit dusty. See this one is white plastic where the other one wasn't. So let's just take the screws off. This is in beautiful condition. Yeah if you look at the serial number here this one is like 86,000 whereas that one was 1700 so that was to be an early model and this is a much later one. And you will see that this is almost exactly the same. Now the differences are this is a replacement buck regulator I put in. This one powers the logic. I tried to replace the linear regulator but it's still plugged in here except it can't produce enough power to run the solenoid. So everything worked fine except for the solenoid. I have however attached a heat sink to the linear regulator because it got really worryingly hot. Here is the mechanism. These are the bodges I've put in to put pressure on the stepper motor bearings so they don't skip. I don't need any of that anymore so let's remove it. That was very much a bodge. Okay this is actually epoxied in so that will stay. And now what I'm going to need to do is to remove the motors and solder these back in where they were. So the first thing is clearly to take the module off. Now these screws are much easier to take in and out. I think I can do it with my fingers just stick my thumb on the nut to stop it turning and just undo. So we've got a washer and a nut. The other one I do kind of hope these motors work and that they don't suffer from the same problem as the last one. I thought I would get more torque out of them actually. I'll have to compare with these. So again we have a nut and a washer. So this thing will now come out. I have actually removed the motors on this before so hopefully this should be easier. I said easier. And now I remember that you don't actually have to take the screws out completely although that one did actually come out. And this one really helps now you know now I know how to actually do it and I don't have to dismantle everything. Assuming I can do this one. Come on, too tight. Yeah I'm going to have to remove this retaining clip after all. At least I didn't have to do the other one. Oh yeah. I keep forgetting that this is how you do this. Like so. Carefully lift this out of the way. Undo the screw. This time I'm going to be careful not to lose the loops of wire. Screw is not going around. Actually I'm not sure I have had this motor out. I know I've had the other one out. I unhook the spring. Does that help at all? Not really. I wonder if I need some WD-40. Yeah that's just not biting. Okay let's put this on when I try and figure out what to do. I think I will try a drop of penetrating oil and another short delay because I think that actually helped last time. There we go. I just want to be careful not to get any on this because it might melt it. I think that will do. So short delay while it soaks in and then let's have another go. Alright it's been a little while. Let's try this again in the hope that it works. Huh. That's going around perfectly smoothly now. Wow. WD-40 really works. Let's take that out completely. More or less. Like so. And then I should just be able to lever this off. Okay so we carefully unspool the cables and I'm not going to take them off just yet because I want to compare these. So this one is... I can feel the stepping behaviour of the motor rather more firmly than this one. This one is smoother. What about this one? Yeah for that one as well. Okay let's give us some power and see what happens. Yeah these are generating much less torque than these. It's still not a lot but they are clearly not right. Okay so unplug the power and now we're going to remove these motors. Carefully from the working machine. Okay. I have lost my beloved corner pliers again. I use them for everything so I can't forget them to put them back. No I did remember to put them back it's just they were under something. Okay. I should get some more of these actually. It occurs to me that I didn't check to make sure the colours were the same as on this. Red, white, blue, yellow, black, black that seems roughly correct. Okay so that over here is the defunct one. Now I need to clean this up a bit. I also really rather want to get these out of the way while I solder. Yes I'll remove those because I don't want to damage the wires by accidentally touching it with the soldering iron. So let's try and remove the leftover solder. At least this stuff melts. Yeah that's cleaning up quite nicely. Okay let's apply some flux which will melt instantly because the board's hot. So here is the working MOSA. I want to re-tin these ends with fresh solder. Nothing particularly exciting here it's just a bit fiddly. So and re-tin the pads. Once this is done then we should just be able to touch the wires. Apply heat and they will bond hopefully. This one, this one and this one. Okay right. And again this has to be left-handed which is annoying but touch that here. Seems to have worked. Get the white wire out. Red, white, yellow and getting in the wires are all getting in the way of each other. Yellow. No wait that's in the wrong place. That's where blue should go. This should go here. Yellow. Blue. Oh hang on. This is, that's the black wire for the stepper motor. We actually want these to go here. So black and the other black. If I remember correctly they are connected together inside the stepper motor. They are the ground wires for the various coils. That's not a good joint I need to do that one again. Now we need to put the stepper motor wires back again. Stepper motor, solenoid. Solenoid wires back again. So this one goes here. Just trying to get the hair out of the way. This one goes here and this one goes here. Oh right. Now let's put the power back and see what it does. Hopefully it will do better than before. Yeah? Yeah that loads more torque. It's not vibrating, it's actually turning against my finger. Good, good that's working. Right let's do the other one. Now this grey and black wire is, this is for the sensor that tells it whether it's at the end stop or not. It's interesting that this set of wires, which are the high current wires that run the solenoid, are thinner than the wires here that go to the sensors. I think that with a bit of care I don't need to, yep that'll do fine. That'll keep the wire out of the way. So corner pliers and remove this one. Yeah. Hands are shaking. One, two, out of the way. Plop on quite a lot of flux. Now I haven't been able to keep the wires nice and braided unfortunately, but that shouldn't matter given the, that shouldn't matter for the length. I just need to check the ordering of the colours. Red, white, blue, yellow, black, black from the top. So that is actually the other way round for this one. So let's go with red. Oh hang on, I haven't really surfaced these. Where did I put the solder? Here it is. Red, black, other black. I always love these mechanical plotters so I'll be really pleased if I get this in working order again. They're so much more satisfying to watch than any other kind of printer. My school had one of these when I was a child and I was basically the only one who ever used it and it worked nicely until the nasty nylon gears went, as they always did. So I was very pleased to get hold of another one, especially in such good condition. A little disappointed that it didn't work, but if this actually fixes it, which I'm cautiously optimistic about, OK, I'll apply some new solder. Then I will have a very nice looking plotter with a new buck power supply that won't get too hot. I still want to find out whether I can get a replacement power supply for the power. Actually, that one works the solenoid. If this one works everything else, that one just works the solenoid, presumably to prevent pulses through the power system whenever the solenoid turned on and off, causing issues. OK, I think we're good to go. These power supply modules are grey import stuff from Banggood, so very likely are underspect. You can get drop-in replacements for these linear regulators that are sealed buck regulators, same pin-out, same form factor, except no heat sink. So maybe I should get one of those and try and see if it works, or just not fiddle with it. But I'm not a fan of those linear regulators. They do get hot. I didn't point it out, but the other plotter, there's a big chunk of metal here. That was the heat sink in place. Black wire, that's not a good joint. Yep, let's pry this one apart and reseat it. OK, and let's apply the power again and make sure it works. What I'm doing here is checking to see whether I got the wires through right around. If I don't, it will judder horribly rather than turning smoothly. So let's see what happens when I turn it on. Smooth rotation, smooth rotation, and the solenoid's moving and everything. I am optimistic. All right. So this then needs to have the wires tucked under there. And I believe under there, so that this then goes into place. I will reattach the screw just a little. Just about that much. OK, so now that goes in there. So there's the brass disc here. Locks into the hole to provide one set of orientation. And this screw goes into that slot to provide the other. That wire hooks around that little notch there. So this should more or less drop into place if I can manage it. No, it's not going. There's a little protrusion which you can just see there. Which goes into this slot down here somehow. So you try it without that screw. This is surprisingly fiddly. There is probably an easy way to do this somehow. I just don't know what it is. You just want to be careful not to apply too much pressure to anything or I might yank the wires out. Ah, no, that didn't work, but it was nearly there. So I can get the little protrusion in the slot. And I can get the brass boss in the hole. I can't seem to get all three at once. It's also important to get the wires looped around the right places as well. If we do this it will twist the wires together and make them a little less inclined to stray. So the way I got it out was to lever the top. So let's get a bit more slack in the wires and try it differently. And just to check something I should have done before which is that the motors do actually have the same mount. They do. They seem to be the same size. Nice click and it goes in place. Let's do that screw up if something horrible happens. I'm not quite sure what I did mind, but at least it's there. And with luck I will not have to remove this again. Lucky says. Okay, the camera died again. So I don't know what's actually there, but I do have, as far as I can tell, all the bits in place. Yes, I was concerned about the pen mechanism not moving, but on looking at it again I believe that's because there is no pen installed. Okay, here is a pen set. So let's load them up. Red goes first. And the spring that actually moves the bar is this very delicate leaf thing over here. So it pushes through the pen. So now I expect that to move rather more than it is. I wonder what's gone wrong here. That feels bad. Very bad. Okay, well, the next one is black. It's possible I've got black and blue the wrong way around. Just red. Black. Blue, that is blue. Now for this one must be green. Put the green in place. Let's feed in a little paper and power on and see what happens. I can't help noticing that something is not right here, such as the fact that the paper is feeding in the wrong direction. That's kind of odd. You know, I think this is trying to change pens, which is supposed to push against the pin on this side. It's just backwards. Everything is backwards. I think I've wired those motors in the wrong way around. And this is not right. The bar's not moving at all. Yeah, this thing, which connects the solenoid to the bar, is broken. Okay, let's get the paper out and take the thing apart again. Somehow that screw is still there. There's a screw there for some reason as well. Okay. So here is the left side. It's a red, white. I swapped blue and yellow. What did I do this side? I swapped blue and yellow. Yeah, okay. That's at least simple to fix. So that will keep the wires out of the way. I need the suppliers, the yellow wire. Interesting, so I made the same mistake on both sides. Well, I copied the wire color from one side to the other. So I made the mistake on the first side, this one. And then cop duplicated that on the other. Okay, those are swapped. Now this side, move yellow that round. Yeah, this isn't particularly nice, but should work. Now, what can we do about this? I know exactly what's wrong. And I will hopefully, if I can get this off, show you. Wow, that's stiff. The whole printer mechanism is amazingly cheap. It's quite elegant, but it's cheap and delicate. Okay, so this is the solenoid. It's a simple coil that pushes this permanent magnet in and out of position. This is a keyed cam that goes onto this miniscule. Can I get that to focus at all? Probably not shaped bar end, which is connected to this. So this moves backwards and forwards and it's split here. Now, it was like that when I got it. And what I did was I very carefully super glued it back together. But rather than do that again, I should have a perfectly good one here. So let's open this up and see what there is. Okay, this is also a slightly different style. Oh, that's interesting. It doesn't work the same way. That's quite different. Sorry, you can't see that. So this has got this spring, but there is no cam in there. Okay, let's take this off and see what it looks like. I'm going to have to remove the module. But as I didn't bother to do the screws back up again, that's easy. Oh, now that is interesting. This does work quite differently. There's still got the shaped cam, but it's a different kind. Instead of being a single bar that hooks onto the... Instead of sticking up and hooking onto the... What did that hook onto? So this went on like this, like this, like this. Right, the solenoid arm which goes on like this moves out and it pushes this around like that and moves the bar. Now this one does the same thing except the bit that moves is this plastic piece which has in fact locked in place. It's... Also the bar here, which it moves, is plastic rather than aluminium. And I see it's split in a few places. That's completely jammed. Probably wants more lubrication. So if I can get this off, I should be able to reuse the same mechanism. Right, that is coming off, like so. However, I probably also need to swap the little plastic thing that goes on the cam, cam stepper motor, because this one has this little pin sticking sideways that goes into that thing, where this one does not. OK, so can I get this off? Does it just pull off? I think it might friction fit. Or I could just replace the stepper motor. I keep saying that solenoid. I think that's probably the best option. Is that coming loose? Let's just replace the stepper motor as a whole. Stepper motor, solenoid. These are stepper motors. This is a solenoid. They're not the same thing, even though they both work via magnetic coils. OK, this is a known good, but one that doesn't work the way I want it to. This is an unknown one that does work the way I want it to. So I need the little plastic bit that I pulled off. This goes on here. Then this, with the little pin, goes on here. So when the solenoid thing moves here, you can see the pin moving. So let us screw this back into place. Let us painfully screw this back into place, like so. And then reattach the solder points. So cleaning these up with some fresh solder. I did these earlier. So all we should do is straighten the wires. This down here, and eat. And this one goes down, and eat. Right. And the other bit we also want to move is that spring. This. I don't know what it does, but they thought it was important. Probably assists in returning the unit back to its home position. So get this out of the way again. Luckily the new case still has a hole for it. So now let us attach the plotter module again, like so. Feed in some paper. I won't use the entire roll this time. And try it again. Okay. Now what is it going to do? Moving the right direction. Right. Well, this is not right. So when it wants to change heads, what it does is it brings the pen back, and then it moves the head over to the left here. See, each time it does so, it rotates the head mechanism a bit. So three of those, and it changes heads all the way to the top. However, this is not happening because the head's not moving back properly. Why is it doing that? It's now lost its homing. Yeah. That's not good. That's supposed... Right. It thinks the head is not touching the paper. I have an idea about what's going on in there. I was reasonably sure that black was the one on the left. So I think what was happening is they got the polarity here wrong. It was vaguely under the impression that these things ran off... It ran the solenoid of AC, so the polarity doesn't matter. Actually, I think I have a photo of that. Yeah, we go. Come on. Red is on this side. Yep, I got that the wrong way round. So that was a fairly simple and straightforward mistake. Goes back into place. The cable hooks around there. Let's stick the paper back in. Apply the power and see what happens. That's working. Black box. More air for blue box. Green box. Red blocks. Okay, this is looking extremely promising. So let's try that again with the self-test. You see, I pressed the right button. I think I didn't. Well, right. We now get a blue box. There we go. The pens are very elderly. I haven't used it much because it doesn't work. But once it gets a chance to run in a bit, it should be better. Inefficient piece of firmware there. Beautiful. I think that's working. It wants some new pens, but I think it's working right. I'm going to zip it up. And I'm going to see if I can make it print this thing again and see what comes out. Fantastic. Okay, we need some bolts. And some screws. And you know what? I'm just going to fast forward this bit. Well, here it is all zipped up and finished. And I'm very glad to say it works perfectly. Here is the plot I showed you before with the Tektronix logo. And you can see that none of the lines meet up properly. It's all smeared anyhow. And here is what it produced after the repair. And you can see that everything meets up. All the individual elements are clear and properly arranged. I am extremely pleased with that. I actually did not film it plotting this, but I did film it plotting something else. In Gloria 60 FPS. And I will link to the 60 FPS video in the description below, but I will include a 30 FPS version after this. So, I'm going to call that finished. I hope you enjoyed this video. Please let me know what you think in the comments and stay tuned for the plotting video.