Fixing the Atari 800 keyboard (Mitsumi membrane)

well hello and welcome back to adrian's digital basement this is part two in the atari 800 repair series i hope it's not going to be a series hopefully it'll just be two parts but in part one i took a look at the atari 800 that i've had for quite a number of years that never had a working keyboard and i discovered that the motherboard is actually totally working fine and that the problem lies with this keyboard so in this part i'm going to dig into this keyboard see if i can get it working i've done a little bit of research and it looks like there are at least three different types of keyboards for this machine with one type being more unreliable than others and i think that is this type so i might not be able to get this keyboard even working in this video but i'm going to try so without further ado let's get right to it [Music] all right that means it is time to try to service this mitsumi keyboard so this is all pretty run-of-the-mill stuff oh it uses a little phillips head so this is exactly like every commodore keyboard i've ever worked on all those pet keyboards and things like that you just start by taking out these little screws alright so with commodore keyboards they put a little piece of tape over these wires here but there's this sticky foam here i am sure that there's going to be a screw under here somewhere looks like someone's already been in this keyboard well that's intriguing so is this a problem that has already happened once before let's see if the pcb lifts off now there it comes oh no it's a membrane under there oh no i just was under the assumption that this was like the commodores that's not good everyone all right well let's see what is possibly going wrong here so things are pretty clean in here i'm not seeing a lot of gunk or anything now each of the little sliders here just has a little nub on it which basically pushes onto these little contact points on this membrane so there's a top side and a bottom side of the membrane and when it pushes on one of these it's supposed to make contact there's a strip right here and i think that connects this top membrane to the pcb underneath which also has carbon tracks on it and then that is what routes to the connector here so obviously maybe what's happening is simply this is not being pushed down hard enough looks like there's like a plastic ridge right here that does that pushing perhaps i need to put some little foam or something there to make it push a little harder now what i can do is i can connect this to the motherboard which i'm going to do right now and that way we can kind of experiment and move the keyboard out of the way here we should be able to experiment with how hard we have to push on that little strip there if it's even possible at all so first off let's get this computer working again so i've reconnected this power this on okay we got the ready screen now for the keyboard connector all right keyboard is reconnected there i put a little deoxide in there just so it's a little easier to reconnect all right so let's power this on now obviously when i push on keys wait what that's actually working well one key worked uh oh i think i plugged this in upside down oops well that's interesting that it even worked at all though like i didn't have a single key working before boy and even with deocca that's impossible to get off there we go okay here we go again try number two so plugging it upside down you're gonna get weird readings obviously so that's the space bar wait a second everyone this is working now this makes no sense could the problem have been oxidization in the connector right here and putting some dioxide in there did the trick yeah this thing seems to be working now i'm totally confused by that i just assumed that something were very wrong with this membrane but it seems like all the keys are working okay i'm just gonna clean out the dust a little bit more and i'm gonna reassemble the keyboard and we'll give this thing another test all right the keyboard pcb is back in so now i'm gonna reconnect this here and we'll see if this thing has gone back to non-functionality or stays working there we go look at that how interesting is that that when it wasn't together it was working and now not a single key is working let me just make sure that it's connected it is well that camera battery ran out just there so uh when i plugged the keyboard back in when it was reassembled it didn't work actually one key worked the equal sign and i think maybe a couple things on that row and that's it so i took it out again and i just want to retest this thing without the pcb attached to the rest of the keyboard let's see if this thing works again all right it does it does work this is so strange and it's pretty sensitive too you don't have to push very hard on these keys or to actually register a key push so the question is if i push down on this with my thumb does it start stop working no it's still working ah this is very strange and i gotta say i really hate these kinds of keyboard membranes for this exact reason just weird weird problems just twisting the board thinking that maybe there's a problem with like a broken trace or something on it but it really seems fine any kind of bending i do doesn't affect anything all right i have an idea i'm just gonna hold the pcb into the back of the keyboard here okay there we go i'm just holding it in place i just want to see if typing letters actually works it doesn't so is the problem that the little rubber nubs on the back of the keys don't push down enough on the pcb could it be that what the heck is going on okay i'm getting a p i am pushing on the back of the o key pretty hard and yet okay the p okay you know what it sort of starts to work it's very strange okay so now o is working what about if i push over here very strange but if i take that off obviously we're having no problem at all but maybe what the problem is is that this membrane is worn out and when i push on it with my finger i am pushing a lot harder than that little rubber thing on the back of the keyboard the keys themselves can actually push onto this it's weird because it's not like i'm pushing with much force and i'm getting key presses so i don't really get that now we look at the sliders there i mean the rubber is supple and it definitely extends quite a bit beyond where the pcb is so it should really push down onto it i'm just holding my finger here to see how much force it pushes with it's not a lot actually it's pretty gentle i don't know though it's just i'm pushing so lightly on these and they're registering without any issue okay and look at that i i pushed the a i pushed the a a bunch of times and now it's fine that's so strange wait look they're all working now i don't understand what's happening here now the keys are working with me holding the pcb in place the numbers like one is not working reliably but the screws aren't even in right now if i push it a bunch of times it starts to work this is weird i'm gonna put the screws back in one more time otherwise i guess i have to order a new membrane i mean i don't know if that's even something you can get i'm assuming it is because uh i think the atari community is pretty good like there's a lot of support for it not as much as the commodore but still a decent amount all right i've only put in about half the screws along the top part of the keyboard where the number keys are and stuff so i just want to see if it's sort of working right now or if it goes back to completely not working okay it's back to not working again this is so weird i mean it was literally working a second ago this is obviously some kind of a physical issue and we actually got a cue out of it and that was it no more key pushes after that i'm gonna take some of the screws out see if that changes anything funny when the keyboard was upside down i was actually getting the number two key pushed and it stopped working now so now we're back to just not a single key working and while the screws are out i can tell that pushing on the keys actually is moving the pcb so i know there's force coming onto it all righty no screws are in now and we're getting no key pushes and but if i push on the pcb myself we're getting key pushes see if it's anything through with this wire here nope the wire is not the problem it really just seems like the way these little sliders push down on the membrane is just somehow not enough force or this is not aligned properly okay so what the problem appears to be is somehow there's an alignment problem because if i push the pcb they're little dowels that align it into position but if i push it up now some of the keys are working so i'm pushing one right now on the keyboard and you can see one's appearing on the screen if i push the keyboard pcb down onto the dowels it stops working it's almost like that membrane that's on here is misaligned i wonder if someone opened this thing up and they applied a new membrane and the membrane is somehow out of position you know looking at this i really don't think that's the case i mean all the screws are in perfect perfect position the only thing i can think of doing here is cutting away the dowels there's one there and there's one there and obviously the screws will hold it into place and maybe that will allow me to align this thing in a way that's gonna work all right i did it i cut those two dowels off so they've been removed so let's put this back into position here and let's see if i hold it into place okay fd the some of the keys are working so what i'm going to try to do is screw this in and i'm going to keep the screws loose because this thing can move around a little bit and then perhaps i can get it into a working position and then tighten the screws down all right well i have some of the screws tightened and certain keys work but still very problematic and i think the problem is is that these uh the screw holes don't offer enough leeway so to speak and unfortunately this just doesn't seem to work no matter how i position the pcb and the tiny amount of space it can move maybe i can get a couple keys working but it doesn't seem to be enough and i i just i can't explain what's going on here i don't i don't really get it i think i've got it as good as i can and uh a bunch of the keys work now but a bunch don't work like t works but q does not hey does uh does seems like a lot work some are kind of intermittent like space doesn't work at all i think the membranes just shot my feeling is that probably the one spot where the little rubber thing pushes down onto the little divot is no longer working and potentially when i push it with my finger i'm pushing on a larger spot than the little point the rubber point that are under the sliders and that is why moving the board around makes it work a little bit because it's now pushing on a spot that it wasn't pushed on before well i'm going to put back the rest of the screws and we will just see if anything is improved when they're all back in or maybe it'll go back to not working at all all right all the screws are back in let's flip this around i'll just rest this on here i guess and it's worse oh no well wait a second okay we have no enter key this yeah okay it really is not is not happy if i push the keys a whole bunch of times like the s starts working there okay well you know what it's coming back to life here like the one and two which i slammed down on are fine and enter is fine i don't have to slam it anymore and it actually works huh what a strange problem but that's what you get with keyboards when they're not mechanical with sliders that actually have little contact pads this these have like carbon paint or whatever on them and it's just not a very good long-term solution all right so keyboard is not working very reliably i've done some research it seems like the membrane starts to get oxidized underneath and it doesn't work very well i hadn't really seen anyone trying to move the pcb around like i tried to do which sort of restored it but it seems like i'm gonna have to try to peel off that membrane and maybe clean the contacts or maybe a little bit of sandpaper like just just the tiniest amount something like that to remove that oxidized layer so first thing i need to do remove the pcb from the keyboard once again there appears to be two other types of keyboards that are used on the atari 800 so there's three types total and the other two aren't without their issues but it seems like they are less problematic than uh this mitsumi one this one seems to be well you know i don't know it's there's not a lot of information i could find but it seems like people complain about this one not working the other ones um like there's a stackpole one and stackpole keyboards actually have metal contacts inside so they're relatively easy to keep working i think the problem with stack poles is they have these like square sliders um a little shell part and that can start to crack and break anyway as i am furthest from an expert on atari stuff if anyone has familiarity with this mitsumi membrane keyboard and you know of fixes i guess put a comment down below but at this point i'm just gonna go for it and uh try to peel this off so what i don't know is that does this membrane normally come off freely when the keyboard is new like does this stickiness that's happened on here happen over time now the corner here does lift up without any issue but i'm afraid of peeling it more so i'm gonna grab the heat gun here this one right here it's a crappy one from harbor freight and i'm gonna keep it at a good distance from this i don't want to melt anything and i'm just gonna try to heat this up so in case there is a little bit of adhesive on there should free it up hopefully all right so this is warmed up quite a bit and i started to lift it and right away it started to tear like right there so i'm going to grab a little i don't know flat bait screwdriver i guess and i'm just going to try to carefully peel this away and it seems like it's getting stuck where the screw holes are it seems like the construction of this thing is there's a plastic mylar layer on the top and then this white stuff it's sort of like a rubbery sticky material that's what's getting stuck so what's tearing is not the plastic mylar on the top which actually has the traces it's that middle layer which obviously is there as a buffer to lift the mylar off the pcb so that when the keyboard is sitting there and you're not pushing on a key that is not actually making contact and this is really fiddly yeah it's like a rubber layer almost i think the trick is i'm going to heat it from the underside as i peel it up that seems to kind of free it up without tearing it this is set for 115 degrees celsius i'm just looking to see where the next screw hole is there we go now as i peel it off i don't want to peel it right here where it's making contact because i feel that that will be a little bit harder to read here so i'm going to be careful here i think that's actually all of the screw holes loosened oh except for this one up here probably yeah let me do that one unfortunately this one sort of tore all right so there is the membrane so those are the i don't know carbon contacts and they touch the pcb here now everything looks really nice here i don't i don't really see why this thing's not making good contact in my research i was reading that people just did a little bit of abrasion on these black spots here that contact this and that seemed to do the trick you know i i am skeptical to be honest i feel like this entire thing is going to need to be replaced but it's worth a try i guess all right i grabbed some 1 500 grit sandpaper here i just cut a tiny little strip post i was reading about this said that it was the fact that it gets stuck down and it can't slide around at all and that's actually why uh it's not working because you know there has to be a little bit of give in the plastic when you push down on it with the key whether that's accurate or not i don't know um i suppose what i could have done is once i peeled it off i could have just put it back together seen to see if that made any difference as far what i'm doing now i'm not even there's no sanding going on i'm literally just using the edge of this sandpaper just to mark it up so i could see little sort of very faint scratch marks it looked like at some point in the past there was potentially a group buy of some new membranes but um that seemed like to be three or four years ago and i'm not even sure that it actually happened like someone was looking to have someone manufacture some new membranes for these keyboards okay that's all those done i think i'm gonna just give this a little bit of a clean get the oils off that i left on there now of course i'm not going to clean the membrane i'm just going to clean the pcb just a little tiny bit of 99 ipa everything is super clean under here because of course the membrane was sort of stuck to the pcb so no dust or anything was getting in here and the space bar is up here at the top all right well i think that's uh that's going to be it at least it's free now well it's not free to completely move because still adhere it up here on this contact but on the rest of it it can sort of slide around a little bit so maybe that helps let's put it back together the keyboard's packed together and i have all the screws on but they are only lightly applied so the pcb can move around ever so slightly alright keyboard is connected it is now the moment of truth this is a test no kidding does it it seems to be working wow okay um i'm gonna tighten all those screws and let's see if this keeps working space bar enter whoa i i had little faith very little faith that this would actually do anything at all all right screws have been tightened now it's the moment of truth part two turn on the computer here we go this is a test of the atari 800 keyboard wow oops i thought it hit enter but i actually pushed the caps lock key there so now we're in lower case all right let me just go through and push all the keys so far so good i can't believe this i can't believe this freaking works i thought that whole thing was a goner and this computer would need a whole new keyboard uh-oh that is a v key that does not work so b and c next to it work very well so far every other key is okay what does this atari key do exactly i'm not sure okay shift oh it seemed to have inverted the text okay well it's working caps lock you know caps lock is not working well either you know what that just might be because i don't know how it works okay you hold shift and push it okay so that is working fine so you push it once you get lowercase shift and that and you get uppercase okay control okay we're getting special characters i assume that's good this shift key that seems to work spacebar is working okay so the key that's not working is v and i mean it works if you push it several times so i'm going to loosen the screws i'm just going to move the pcb slightly and maybe that'll fix v seems to be okay now to be honest oh escape also is not working so great if i push it lightly nope but the rest of the keys you don't even have to bottom them out for them to register and the tab key is fine okay so pretty much everything is fine i'm just going to try that that repositioning now that the dowels are out and let's see if that helps those keys could be that i didn't like sand enough or whatever all right i sort of pushed it up towards the top as i tighten the screws down let's see how that works now that did the trick now v is very easy to push escape not so much who cares escape's not like a key you use very often i guess i should test every other key again though because maybe moving it has caused those to stop working i'm only gonna lightly push every key i'm not even gonna bottom the mount just to make sure it registers properly yeah i mean i can't believe it but this thing freaking works i wow okay i'm not gonna i'm not gonna say it works totally until i completely tighten every screw on here back to the way i had it and just make sure that it doesn't degrade by tightening these oh yes this seems to be working i can't believe that peeling it off and maybe scratching it or one or the other seemed to repair this keyboard un freaking believable actually i think the escape key works fine i think you just have to push it twice on the atari before you see the character on the screen that's what it seems like it's doing i don't have to bottom it out for it to register so even that is fixed i can't even get it this is amazing i think this computer is done i'm going to reassemble it now alrighty the machine is nearly back together and before i put the top cover on i'm just wondering if maybe i can take a little piece of foam and lay that across the cards here just to give them a little bit of stabilization all right i cut a little piece of the chamois here how about this this is uh not gonna disintegrate over time because it's like polyester or whatever and maybe i can just lie this right across these uh little raised nubs on the cards here like that and that will just push down on this metal plate here so let's see if this thing now fits over here it seems to go on there and close without any issue but i don't know as if it's even making contact what if i put two on one side here yeah definitely with two there it's definitely kind of lifting this up slightly so i guess uh maybe one will be fine and i'm putting them in these positions here because that's where the tabs are right there and there and plus the two screws that hold this down are there and there and if we close that i don't have the screws on here let me just shake the computer i don't hear any kind of wobbling or anything so we're gonna call that good and there we have it a repaired atari 800 where the only fault with this machine was simply that keyboard membrane that wasn't working all the other electronics in this thing were still working perfectly after all this time quite a forward thinking design on this original machine with the four joystick ports the full size really nice feeling keyboard and of course the dual cartridge slots that are inside this machine left and right although the right never ended up being used for very much and then behind this cover of course we have the four expansion slots for user upgradeable ram and rom which simply is accessible by taking two screws off the top here and let's not forget the video output on this machine which of course is s video compatible with chroma and luma which is very forward thinking for 1979 along with this serial i o connector here which allows you to connect a whole bunch of peripherals and they actually run at a pretty decent speed i remember i had mentioned originally that there was a speaker inside here and i didn't remember it doing anything well that's because of course the keyboard wasn't working and it seems to be used for an audible keyboard click which probably would have been very helpful on the atari 400 with that flat microwave oven style keyboard but really not necessary for a good feeling keyboard like this luckily it's probably as easy just unplugging that if you don't want to hear that beeping at least on the 800 while on later retirees i'm pretty sure that that actually came out of the audio output from the video jack and indeed after reassembly this machine seems to be working properly and you know that keyboard really feels nice i gotta say this is probably one of the better feeling keyboards on these old machines from the 70s the apple ii could be had with an alps skcc keyboard like the apple 2 and 2 plus and that keyboard feels better than this but this one is right up there with really good quality keyboards the funny thing is the 800 xl that i have has one of the worst feeling keyboards i have ever felt it feels like you're typing into i don't know gel or something it's absolutely terrible but this one on the other hand really nice and just like i had theorized with that power supply if we open the top cover here it actually shuts off the machine so there is no danger from you taking cartridges in or out while the computer is powered up you don't have to worry about that causing an issue incidentally if you boot up without the basic language cartridge in you get this memo pad which i assume this just lets you type things on your computer for fun i had lots of comments on my first video telling me that indeed atari released updated basic language cartridges for this machine and there were even third-party ones available as well and unlike machines like the commodore where that's fixed on the motherboard if you want to expand your basic well you know it takes up a little bit more ram but on this machine i think if you put in a new cartridge well that can give you enhanced capability without necessarily taking up more precious ram space on your machine as the final thing i do on this video i'm going to put in the game cartridge defender here from atari into the left slot there we go there it is it just booted right up select game and press the start button i'll just hit start look at that immediate death i i never was good at this game this is not a terrible version of the game oops i was trying to rescue him oh he survived anyways i think i have this on the easy difficulty level too and look i just keep dying immediately i actually finished that level and that is going to be it for this video i'm really excited to finally get this atari 800 working after having it for a good number of years i hope the keyboard repair is permanent or at least lasts a while because i think there's really nothing else i can do other than replace that membrane entirely so if anyone knows of a place to get replacement membranes for these mitsumi keyboards on the 800 definitely put a link or put a comment in the description boy i'm always messing this up put a comment down below that's what i'm saying i know i've mentioned this a bunch of times i absolutely love the way this machine looks it's probably one of my favorite home computers of the 70s even more than the iconic apple ii plus which i really like as well but something about this one it just it screams they put a lot of effort into making this machine good and it's so capable compared to the other machines that were out at the time and even with the 64 you can argue that there's some areas that this is actually better than the 64 but of course this has the pokey sound chip which is not nearly as capable as the sid now i'm sure i am going to incite a flame war in the comment section about these comments but i think overall the commodore 64 is more powerful than this machine but we have to remember it came out three years later technology was moving really quick at that time so that's that's a long time in 80s and 70s technology and even then like i said there's still stuff that's better about this like the fact that it can display colors out of a palette of 256. that's pretty amazing for the time i mean i can't think of any other home computer that had anything even close to that until like the amiga came out for instance so as i mentioned at the start of this video there's going to be a lot more atari 8-bit content coming up on the channel not necessarily right away because i don't like to overload the channel with like one type of computer but i have all those other machines i need to get to i need to at least test them out and see which ones work and which ones don't and then i can tackle some actual repairs or maybe some upgrades like do a ram upgrade on the atari 400 fun stuff like that so if you liked this video thumbs up if you didn't you know what to do subscribe all the usual stuff huge thanks to my patrons their names are scrolling up the side of the screen as you saw at the beginning of this video i actually have merch now so i have t-shirts and stuff you can buy so there's a link down below for that as well and you know all the usual stuff so that's gonna be it stay healthy stay safe and i will see you next time bye [Music]

Channel: Adrian's Digital Basement

Views: 46,251

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Id: OcA4_gsH_Hw

Length: 32min 11sec (1931 seconds)

Published: Sat May 28 2022