Five bad Commodore 64s. One hour. All fixed!

well hello everyone and welcome back to Adrian's digital basement on today's video well you might notice I have some 64 C's on the bench here there are a total of five of these machines they're all broken feels like I haven't done any 64 repair videos in quite a while so let's see if I still remember how to do it and see how many of these things I can get fixed in this video so without further Ado let's get right to it [Music] all right so I haven't opened up any of these machines but I have done some rudimentary troubleshooting by just turning them on so this one here is a black screen this one that I have down here is also black screen incidentally these are all I think they're all short board machines because these have the later cost reduced keyboard that has the petsky characters printed on the top side I must say that these types of machines aren't as common as I think they are outside of North America by the time the Super cost reduced 64 came out not a lot of people were buying these machines anymore I think most people had moved on to 16-bit machines at that point so it doesn't seem like I get a lot of these here in the basement but I know in Europe especially like Eastern Europe these machines were going strong for a good number of years this one here says bad keyboard CIA issue can't type so it could be a bad keyboard or could be a bad CIA but I obviously had that one powered up and I at least got the basic screen and then this one that's sitting right here says also bad CIA no flashing cursor so that could be a very simple fix as well and then finally this last one here says bad power switch so I guess the power LED didn't seem like it was coming on and I guess um maybe no video output so why don't we start with one of the machines that has a black screen when I do troubleshooting on 64s my favorite tools are an oscilloscope the diagnostic cartridge which includes the dead test cartridge this is a double-sided cartridge of course you need a reliable power supply which I have my home built power supply right there on the bench and you need a good reliable way to display the video output and I'm going to be using this cable here that goes into my retro tank now before I test out this machine I always do recommend that you validate that your video display power supply situation is working properly if you only have one machine that's a little bit hard to do of course uh that's not the case down here in the basement so I'm going to use this machine here this is my zif64 if we pop it off here this does have an fpga replacement for the vic2 chip I will make a video about that shortly but for now I'm just going to plug this into my power supply and to the video output so we can take a look at the way it looks where the cable go there it is many times I have tried to troubleshoot computers and I didn't have the connections right or like the video capture device wasn't working correctly and wow that certainly seems like my machine is having an issue you could ignore the problem there okay well I know what's happening here and uh what's happening you see all that that random text that is coming from the fact that this CIA right here the one that handles the keyboard let me unplug it move it around in the socket put it back down I think the zip socket is failing there we go the machine is working now yeah it's working properly anyways we're getting a good solid video capture although it's funny there's black borders but whatever we can ignore that so I know everything is working power supply is good video capture is good that means we're ready to test the first machine all right first things first let's open this machine up and take a look inside oh it has torx bits yeah I always forget the 64 C's have torx bits for the uh the case Fasteners now I don't know the history of any of these machines so I don't know if someone's been in here I'm assuming someone's been in these things but as I've said many times before 64cs are quite reliable so it's not they don't generally fail if you're going to look for a 64 to buy I would try to get one of these if you're okay with not having one of the breadbands because it's just it seems overall like these things are more reliable the case is kind of clipped together you have to pop the Clips off on the sides the fact that this one is quite stuck means that I guess no one's been in this thing so we have a little bit of corrosion inside and oh yeah this keyboard is screwed down to these mounts and of course the inside screws besides this uh dust right there they are Phillips now what's funny about these shortboard machines is I can't easily just go tossing out the heat shield or the RF Shield like I like to do and there we go it's definitely a short board only takes up this little bit of space in here both motherboard types do fit in here but the problem is is these brackets here are required to hold the keyboard up now you can 3D print Replacements so if you want to install a long board into here like say one from a bread bin you have to print some new brackets and these are attached they're actually like riveted on to this Shield here as well so I can't even just toss the shield out very easily which is kind of a bummer what I have done in the past people are gonna probably criticize me for this but I've actually like cut away part of the shield right here so I could install the brackets again use the metal ones and ditch the rest of this because I just don't like this the cover that this covers up the motherboard I feel that like it hinders the already bad ventilation that you have inside 64. now I'm going to say that this machine is probably untouched or if it was touched it was touched a very long time ago because um well it all looks like it's pretty unmolested you don't see a lot of fingerprints and things in here there we go uh funny that this has a little trap door so to speak I don't know what that's all about you can obviously remove that if you want more ventilation there so it does have these little tongs or prongs or whatever you want to call them that touch the various chips and you see the white thermal paste there it doesn't really do that much I suppose it has a little bit of a heat sinking thing but really minimal especially after this long that is all crusty and uh it's no longer no longer particularly effective any longer all right so the motherboard should pop out there is the bottom part of the shield we're going to leave that out pop the board there we'll just get a little bit of the lay of the land here so this is the pla this large IC here this is the dram 64k it's made by sharp this is the older of the two versions of this motherboard the pla here has external character or color Ram that is that's this I see right here the later ones actually integrated that right inside the pla so if you do have one of these machines you need to order a replacement pla for some reason make sure you order the correct type because if you order the one like this that has the external color Ram it's not going to work on your board if the board doesn't have the footprint for the color ramp but that's really only for the much later versions of the short board this one appears to be from maybe 1988 or so I think they were making these short boards all the way up into the early 90s until Commodore folded basically and it was those later ones that had the integrated color Ram here there's a little a little bit of corrosion on the board just in the corner here but that RF Shield had a little bit of rust on it as well so it might be related to that and the back of the board yeah this looks pretty much pristine I don't see any evidence of rework if anyone did rework on this thing they cleaned up their work very well afterwards yeah this unmolested pretty much the sport alrighty so the note I had on there because I had done some pre-testing turn the power switch off um was that it has a black screen let's just validate that that is absolutely the case by powering this up oh I have it in the wrong mode again there it is in fact we don't even see that line that's on the left side I think that that's a setting in here I'm just going to quickly hook up my other 64. I just want to get these settings aligned properly so I can see that white line I rely on that white line to be visible to help me in my troubleshooting so on my zip 64 I'm just putting the original Vic 2 chip back in there okay there we go I'm happy with those settings now the picture's also filling up the whole picture so yeah we're getting the white line if we turn it on there you see the white line and then the picture shows up normally I keep that stuff cropped off actually if I'm just normally using a 64 because you don't need to see that but that white line is a good indicator actually because if your Vic 2 chip is working then you're gonna have that white line time if the Vic 2 chip is dead for instance or not working at all then that white line will not be visible when you first Power the machine up so if we go back to this motherboard here the one we were just testing and we plug this black in we're going to see the white line I know that's going to show up because uh there it is now the fact that it's sort of black is okay or gray there that's the auto leveling or whatever on the Retro tank this particular one see how it's fading away that is not a problem on this particular board alrighty cool so we have obviously a working Vic too we have a working clock if the clock generator which this I see right here that I have my finger on or not working I can demonstrate by just popping it off the board it's in a socket if this chip were bad well you're going to get a black screen but you're going to get nothing in fact we have no picture at all so the machine is on right now but there's no image even it's not even locking onto an image you've had a CRT you would just see a black screen this is necessary for all the clocks to work on the machine the IC is an 8701 and what this does is it takes the clock which is right here here on the motherboard and it divides it up and does what's necessary to then go into the Vic 2 chip which is then what generates all the clocks for the video of course and generates the video signal but also runs the CPU and stuff like that so you need this chip to be working but you can kind of tell when it doesn't because like I said the computer doesn't really do anything at all so I pop that back in the board and we turn this back on and there we go we're back to where we were before with the white line but the black screen otherwise all right first things first typical problems with these machines while black screen can unfortunately be caused by all sorts of issues but one of the things that typically goes wrong is the dram goes bad and I gotta say the dram on this machine is now getting very very hot so with that said I'm going to say these two sharp dram chips they're 4464s are bad now just for fun let's plug in the dead test cartridge here dead test I have a feeling it's not going to do anything because what happens when the dram goes bad like this is it just basically kills the data bus so let's plug the video back in turn this on all right we're actually getting flashing so it didn't kill the data bus entirely but the dram is really really hot and this dram on these later machines shouldn't even get warm in fact like these other chips none of them are warm except for the dram anyways the flashing there definitely indicates a ram problem but the fact that they're hot if you turn your machine on and they're hot you just might as well just swap them out okay sockets are installed I put some dram chips in there that I think work I think plug this in and see what happens okay look at that we have a working system all right great I'm going to turn down the chroma decoding here on the Retro tank I am not super happy with the 5x this was a donation thank you very much uh Seth for saying that in but it's it's problematic it just does weird stuff like why did I have to turn the chroma way down on this particular board I don't know the the other one didn't seem to be as finicky as this either way uh we have a flashing cursor we have Ram that's not burning hot test harness is connected and I have the diagnostic cartridge in here power this up I'm predicting that this thing is going to work without any issues I do not have the audio connected so that is one thing we're not going to be able to hear but the Sid chips on these are also super reliable and we will do the dance party once this works I think we're good and just the last interrupt test okay there we go it's doing the sound test I have the easy flash 3 cartridge in here in my new pink case thank you very much Sloopy for that I have the audio connected up to the speakers as well plus I plugged in the keyboard that was from the case I just took out turn on the system and we go to Adrian's tools 8-bit dance party here we go [Music] thank you all right so uh yeah that sounds absolutely normal the uh the SIDS on these later machines sound a bit different than the ones on the bread bins but that's just par for the course and it sounds absolutely normal this machine is now 100 working the keyboard is even working properly so that's it on to the next machine all right machine number two this one is the one that says bad CIA can't type why don't we crack this open and then see what's actually the problem well this one is uh pretty dirty inside it could well be a keyboard problem that's so that's wrong with this thing like maybe it's just filthy inside the keyboard and that's keeping it from actually working as you can see though this is going to be a short board just like the last one when I'm loosening these screws though there's a little bit of a crack sound well at least there was on that one which kind of implies to me at least that no one's been in this machine either alrighty all the screws are out now look at the color of the PCB it's green as opposed to the yellow on the last one all right so what do we see on this one well external color Ram just like the last one but on the back side looks like completely untouched except for wow you know this is just hand soldered this stuff anyways which is why there's flux residue all of this was wave soldered and cleaned after it was installed so everything looks well pretty good actually as is typical for these short boards everything is soldered in except the CPU the Sid chip and the vic2 along with the clock synthesizer whatever chip that I don't know what that's 8701 whatever that thing's called let's plug in the power let's plug in the video and let's see what happens when we turn this on okay we're getting a flashing cursor kind of implies that this thing is actually going to work so we're going to plug in the diagnostic ROM here and the test harness I am just going to give the contacts a little bit of a clean again because that looks pretty gross oh yeah that's dirty now if we do test this thing and it tests good that means that the keyboard is the problem and I wouldn't be surprised judging by how filthy this is that maybe I couldn't type anything because uh all the the inside the keyboard is just dirty let's see how this tests obviously Ram is good and unlike the last one the ram here which is working when I'm touching it here it's not even hot at all so far so good keyboard it says it's open and the control Port is bad okay so we definitely have a fault on this machine sound test okay I just had the speaker down so that's working okay so it's saying that the 6581 is bad that's the Sid for the paddle ports it's not even it just thinks that the keyboard is open let me just double check this is definitely connected the right way plug that back in all right same problem control Port open and the keyboard open all right first I'm going to do is jump into the schematics now think about the two problems that we're seeing we're seeing that the keyboard's not working and I can guarantee remember from my original note that when you power this up without diagnostic cartridge you can't actually type anything on the keyboard even though the cursor is flashing it doesn't actually sense anything as you type and of course the diagnostic also says the keyboard is open but we also have to think about the other problem the diagnostic cartridge is saying that the Sid is bad and that's because the SIDS handle the paddle inputs the analog inputs now take a look at the schematics here so here's the keyboard connector there's the 6526 that handles that particular keyboard if we look at the joystick controller ports you notice here pot a and pot B these are the potentiometers or the analog inputs that are for the paddles well they make their way up to this chip right here u11 a 4066 it's sort of like a an analog switch device you can think of it that way notice that the potential inputs go to this this would be from the paddles and then those are just connected up to two single outputs that then make their way over to the Sid chip now we may be dealing with two separate problems here these two issues may be completely unrelated but I'm kind of thinking that they're going to be related because obviously we can see on this 4066 these two systems are interconnected now there are two column connections that make their way up to this 4066 and well those are just two column things those shouldn't necessarily break the entire keyboard from working now that I think about it let's hook up a known good keyboard the one from my zip 64 up to this machine and let's just validate for sure what the keyboard is doing we can also try booting up into a joystick tester because you notice here these joystick inputs notice these also go to the same 6526 and yes using the joystick ports uses the same signals on the 6526 meaning they actually conflict with each other you can't use the joystick and the keyboard the same doorway you can but if you push a key and you move the joystick that can actually interfere with each other so let's try to figure out do the digital joystick inputs work does the keyboard work at all as in any keys and I don't have a way to test the paddles right now but we can be sure that that's probably not working because of the diagnostic test which does test the paddles I'm thinking that maybe these two signals here are coming from the 4266 are causing a problem on the entire system like maybe the diagnostic test can't run because perhaps this 4066 has gone bad and it's holding six and seven high or low or something like that so let's get this all hooked up and we'll use the telescope as well to kind of see what we can see going on with this machine alrighty so the system is booted up and I have my 64 keyboard from my zif machine which I know is a good keyboard so we'll plug that in and let's see do we have any keyboard activity on any key oh okay we're getting some and we're getting some strange stuff in fact I'm getting Q all the time on that row all right so we're getting some kind of activity it's not behaving as I would expect but something is happening so I have the zip 64 on the bench because we have a known working computer and the first thing I want to do is show the way the signals look on the keyboard connector when you don't have a keyboard connected so notice here we have rows and columns and what the 64 does and I think I'm getting this correct is it sends pulses over the column signals and they are all happening not at the same time as each other so column zero is pulsing like at this rate we can see right here on the oscilloscope and oh okay the program just crashed the virtual bench this National instruments virtual bench is honestly a piece of junk I have really struggled with this thing lately what happens is occasionally when you zoom in and out and I don't know what the Rhyme or Reason is it will just crash and it's not doing it right now but it just does it periodically and it gives you this runtime error and then basically the program just quits and I have to relaunch it again anything I had set up on there is gone anyhow back to what I was talking about so the 64 instructs the 6526 II pulse each of these column outputs and then it reads at the same time it's pulsing these outputs it reads the row inputs and when you're holding down a key on the keyboard a key connects one of the rows and one of the columns together that's what the key push actually does what happens is the 64 stands out of a pulse on one of the columns and you hold down a key that connects it to say row zero well on row zero the 6526 which is this pb0 line is going to be seeing that pulse coming through if you're not pushing any key then no pulses are going to come through so when we go back to the other machine we're going to expect to actually see those pulses happening on these column pins they're happening on all of these pins if we just touch the random ones you know you see it on all of them now if you go to the row pins themselves you're not going to see anything those are going to look high just sitting here idle but when you connect the key through remember it pulls it down to ground and that's how the 6526 tells could tell you pushing one the keys now since we know that column 0 through 7 should be sending those pulses out those pulses should make their way to the 40 66 as well and I have a feeling those are needed for that potentiometer or those analog inputs functionality to work properly so let's go back to the other machine Let's see if we're seeing those normal pulses uh coming through on those pins because I kind of have a feeling that we're not going to see those and that is going to tell us right there that there's probably a problem with the 6526 which is this chip right here all right so this machine is on the column pins are these ones up at the top here it starts at Pin 20 for column seven and we go on that pin and look at that it's just low so uh see about these other ones Yep they're all low so that's kind of telling me let's look at the row input pins those are high so I think what's going on when we were pushing keys and we were seeing something I think all of these outputs here PA through seven are stuck low and when I was pushing on keys I think the pulling the kernel pulls these PB lines right here looking for key presses it probably starts at row zero and when I push a key it does ground that input pin of course because those column pins are all stuck down at Ground which probably causes the machine to register a key press just because it is correlating a low input on one of those pins there when I push the key the problem is those signals are always low they're not pulsing like they should so it's not going to push the right keys and sure enough that's exactly what we're seeing just seeing junk input now originally I was thinking that maybe the 4066 were bad and they were holding down these two pins that would be six and seven but we're seeing what the oscilloscope I saw all of the column pins stuck at Ground now these pins that go over to the joystick Port you know it's possible there's something wrong at this part of the board and that was holding those pins low but we can see right here that there's nothing connected to pin 15 it doesn't have the joystick or this 4066 connected and let me just double check that that pin is low as well and there we are I'm on pin 15 on the connector and as you can see that is just stuck low all the time now it's kind of unusual if we go back to the diagnostic cartridge I have the computer turned off right now and we boot up to the diagnostic cartridge I can tell right here that the 6526 is working to some extent like it's communicating to the rest of the computer and that's because you see these two clocks right here one that says 24 am and 24 PM these are the time of day functions that are in each of the 6526s there are two 65 26s on the board one that handles the user port and some stuff over here and this one here is handling the keyboard and joystick ports well the times are counting up there if the 6526 were removed from the system or totally dead for instance you wouldn't have a valid time showing up there so that's a really good way to tell that the 6526 is communicating on the bus and each one of these clocks is for each one of these anyhow I think we figured out pretty much for sure that the problem on this machine is a 6526 has gone bad and incidentally it's not warm or anything so that really sucks that it's bad and by the way I keep calling a 65 26 it does say that on here I think sometimes these are labeled 85 21 maybe something like that on the 64c but both of them are the same part they just changed the part number for the 65c they're 100 interchangeable with each other but please do remember that if your keyboard's working for the most part but you have no paddle inputs like the analog input for the Sid is bad then the 4066 which is this chip right here can also be bad so just try to remember that you can see that on the schematic how that thing is wired in but we should be seeing pulsing coming from the 6526 and we're not so I'm going to remove this and then I'll put a socket in and let's see if that fixes the problem alrighty so the socket is in I've grabbed the 6526 for my zif machine even though it was messing up at the beginning of this video that's the socket that's in there it's not this chip I don't think it's that chip at least the original chip is right here it's out of the board it's uh not damaged or anything like that so um if it's actually okay still and there's some other problem on this board it's technically possible then we can go back to this other one now I wanted to mention one thing about this as well is if the pla had a problem and it weren't selecting the 6526 because the pla is required to select that chip then that could cause it not to work as well I didn't actually go ahead and check the chip select line there's going from the PLA and the reason why I didn't is because in the diagnostic ROM when we had that running we were seeing that time stamp updating properly that showed me that the diagnostic ROM Woods communicating properly to 6526 which would not happen if it were a problem with the pla selecting that chip say the read write signal wasn't getting to the 65 26 then you also wouldn't have that time stamp counting down well I don't think you would at least so yeah let's plug this one in I need to crimp the pins on here with this little 3D printed tool that someone sent me in sent in this one was not de-staughtered off another board make sure this is off and it is and that is a pretty stiff socket but there we go it is in there now with the computer turned on we have a flashing cursor I have the keyboard that matches this computer came with the case it's very dirty plug that in it's fully working now so that tells us right there that that unfortunately was a bad 6526 the reason why I say unfortunately is you can't get those anymore um they haven't been made in a long time and you know as far as fpga Replacements go for the 64. yeah uh there isn't yet one I think there's one that's ready to come out it's like in beta testing I have no idea how much it's going to cost it's a cute little circuit board that fits in the footprint of this and we'll plug into the board but this is a pretty complicated chip there's a lot going on on here when it has all these different timers and inputs and outputs on there plus those time of day functions and there's all sorts of things this chip is good for it's pretty complex chip so it's not simple to replicate and you might be thinking why can't I use a 6522 from a vic-20 for instance or 6520 as well those are kind of similar chips to this well they just don't do nearly as much as this chip can do and they are not compatible you can't just put them in it's not register compatible so you have to use a 6526 which are hard to find and they're kind of expensive at this point while we have this connected up I plug the oscilloscope probe onto the keyboard connector and take a look at that there are those uh pulses that we're expecting to see and they are on all the various pins here oops I'm not making a good connection there but yeah there we go so you wouldn't have a working keyboard without those it's not possible so not seeing those pretty much confirmed immediately that there was something going on with the 6526 and of course if it wasn't being seen in the diagnostic ROM then maybe there was a problem with the pla or something like that but it was being seen which definitely points to the chip itself being bad so I have a diagnostic harness connected back up let's power this up and we should see everything good now I don't think there's going to be any problem unless the Sid is bad which I find that highly unlikely that it is and it's probably only going to be a problem with the 6526 as the only fault with this machine look at that everything shows okay now and let's just wait there there's the sound test that's working so boom bad 65-26 has The Only Fault in this machine that brings our total bad parts down to these two RAM chips here and this 6526 so for two machines I'm just going to draw an x on this so we know where that goes and do we have time for one more machine yes I think let's do that I'm going to grab another machine and we'll do three on this episode all right the next machine boy this bench is getting messy here next one is a black screen machine so this may well just be bad Ram again if that's the case I'll Breeze through and get this thing working and we'll move on to the other one that has um I don't know I think it said no flashing cursor which unfortunately no flashing cursor could just be another bad a bad CIA 65-26 hopefully that's not the case because we kind of want something a little more interesting than that but like I said at the beginning of this video these types of c64s are just reliable machines they're just reliable this one doesn't look as corroded on the inside so that's kind of nice it's definitely way less dirty than the other one pop out the keyboard it's all pretty easy I've done this multiple times now one thing that's interesting is the screws that hold down the shield are torques and on so far all the other ones I think everyone I've ever worked on to be honest are actually um Phillips and the keyboard screws the two screws for the keyboard were Philips but they're different the ones that go into the case here have like a plastic thread sort of like the ones that are on the underside and the ones that are for the keyboard go into the the metal brackets here so those are machine screws so they have a much thinner thread but I think everyone knows when Commodore was assembling computers they just sort of randomly threw them together so you know you kind of can't you can't expect everything to be done the same way you know maybe this is a much newer computer let's see when we pop this off a little screw fell out there no this looks like the same exact motherboard type as the other one so we have the external color Ram so this is not like a later version and I don't know everything's looking run-of-the-mill in here so let's just plug this in and validate for sure that we're just seeing that same old black screen and then I'm just gonna finger the two chips here they are a different brands so uh if they have gone bad well you know I guess it's not brand specific at least oh it's already on the power switch was actually on oh those are hot yeah okay another bad more bad Ram all right well I'm just gonna jump cut repair the ram and let's see if that fixes it all right it was quick for you but new RAM chips are in uh the old ones are sitting right here I have not turned this on but as you can see I have the diagnostic test harness connected so let's turn it on together will we see the test screen oh I need to plug the diagnostic cartridge in as well get that in there okay here it is will we see the test screen look there it is came right up instantly so uh definitely unless something else comes up this was bad Ram uh we could see that there are good time stamps there so the 265 26s are good and let's uh turn up the speakers here so I can hear the Sid tune but yeah that's that's a boring fix so so far three machines two have had bad RAM and the ram just got hot this Ram by the way got really really odd like quickly the other one a little bit less so and then we have the bat 6526 let's see oh I forgot to plug the keyboard in I'm just going to plug the keyboard in and we will let this run again just to double check that everything is working on this machine while this runs I'm just gonna put a couple x's on here I know people like to see that and I don't always remember to do it I definitely always do it because I do not I repeat I do not want to get bad chips mixed in with my chips that are probably good so those are X's we're sticking them in there for now um here we are back on the diagnostic screen and I'm sure the keyboard is going to be fine so this machine it's like super clean keyboard okay everything is okay this thing just freaking Works bad freaking Ram all right next up this one I wrote bad CIA no flashing cursor so I just assumed the CIA was bad because the cursor wasn't flashing and that typically happens pretty sure that happens with the one if the CIA on the keyboard the one we've already changed once is bad like completely bad then you don't get a flashing cursor at all so let's open this up maybe it's missing maybe someone stole it uh this machine's in really really good shape looks very very clean I don't even see any yellowing aha look at that this is a longboard machine so let's uh get this out of here fortunately the power connector for the LED is under the keyboard so you can't easily disconnect that not until you've got the keyboard out of here so longboard uh this is exactly the same motherboard that was in my field found 64c so it's a typical longboard almost always it's a typical longboard but the difference is instead of eight RAM chips it's got two so it looks like a normal longboard they just did a little consolidation where they switched to using the 4464 RAM chips so the LED connects under there and let's get this keyboard out of here and this is what I was talking about so these brackets right here are what hold the keyboard up and they're a little different and they are held in with Torx screws as is the rest of the motherboard now my field found 64. that was the one I found in a field well a farmer founded the field and then gave it to me thing was rusted out it was full of ants and everything inside that machine didn't have the RF Shields anymore they were completely gone 100 rusted away to nothing basically so I did have to 3D print the brackets which at some point in the future if I recall someone sent me some metal brackets to replace the 3D printed ones but honestly the 3D printed ones work perfectly well and the nice thing about them is they allow you to take away this RF Shield entirely which can definitely help things out from an airflow perspective these motherboards don't have the later low power chips that the short boards do they're not the 8000 series chips they're just the normal 6000 series chips and things like the Sid and the Vic 2 they get much hotter so when you have them on a under a shield like this well that can I don't know if it causes premature heat death but it certainly causes the chips to get very warm all right so let's take a look at this uh how do we get this out why is this stuck in what happens is the RF Shield that's welded onto the board there soldered onto the board it gets kind of stuck there we go it gets kind of stuck on these little standoffs here and that's because we see right there it's got the little um hole punched out well that falls into there and normally you just slide the board out the short boards they're not actually soldered on to the bottom RF Shield that stays in the case um notice by the way that this does have the standoffs where both types of motherboards now the bread bin cases in Europe also have standoffs for both sizes so you can put short boards into the bread bin cases as well bread bins in North America though don't have these set of standoffs right here they only have the ones that accommodate the larger motherboards like this one there's an adapter plate it's a RF Shield that goes underneath short boards if they were to go into a North American bread bin case a big 20s uzac it's later vic-20 boards are the same size as the uh as the later short boards okay so um just as I said this has got the two RAM chips instead of the eight that are in the later boards there's a little bit of simplification because of that but generally everything else on the motherboard is exactly the same now of course this is the later design that has um well the clock circuitry is all Consolidated into the 8701 just like on the later short boards but otherwise yeah this thing is just a bog standard normal longboard it's pretty reliable because it seems like by the time these were getting made if I could find my magnifiers I wouldn't be surprised if this is like 86 or so 87 on those chips 87 there 87 on this chip and this is 86. so because there's stuff that's soldered down that's from 1987 we can assume that like I said this thing was at the very end of the line now I don't remember really pointing out the date codes on those previous short boards that we looked at but I think they were there was an 89 and there was maybe an 88 or something like that and um I don't think there was any from the 90s so far although to be honest I wasn't paying that close attention and I'm sure people watching this video probably noticed the date stamps on those let's just plug this in and actually do a test let's see how the keyboard is behaving as I mentioned that there was no actual flashing cursor all right and there we are the system booted up so we have the basic prompt and we have no flashing cursor I'm going to stick this diagnostic ROM cartridge in let's take a look and see if we see that time stamp thing so there it is right there time stamp 4422 D notice that is completely wrong that implies right away that this particular chip right here is no good the other one on the other hand which does disk drives and stuff like that is so that's unfortunate that's really unfortunate now from what I've heard in the past remember the joystick ports are connected to the keyboard emblem we saw that on the schematic for the shortboard but it's the same on this board there's possibility that some maybe some static charge or something went into these ports and did damage this chip that is certainly possible I've heard that throughout the years that it was I've never witnessed that myself but that doesn't mean it doesn't happen and I think people can probably attest to that that they were handling their 64 and I went to plug a joystick in and they Zapped the joystick port with their fingers they were going to plug it in and then the machine didn't work after that or like they couldn't use the keyboard or Mouse anymore or Mouse but the good indicator that there was a problem with the CIA was just simply the fact that the cursor wasn't flashing and it's required for the whole timer circuit to work that allows the cursor to flash alright so I think at this point this machine may be a boring fix so I'm just going to jump cut to having a socket in here and we'll see what happens and I was thinking when I was about to take the 6526 out though I forgot to check what I said you need to check which is the chip select line and this being an older machine has the more unreliable pla in it now this being a later of these machines the pla started to get pretty reliable the even the one that this thing uses by this point what 1987 but it still could be bad so we need to make sure that the 6526 I think this is it right here U1 has the correct chip select line now there it is it's pin 23. now if we scroll back down here there it is cia2 and cia1 those are the signals that come from the pla that turn on or chip select the actual 6526s now the normal failure mode for the pla on this like the crappier plas is that it goes low on the output it's now low turns on the chip select to whatever it's connected to all the time so it would have the effect of causing a black screen on this machine if the chips like line that was going to this was always low because that's that CIA chip would be selected all the time and it would basically cause a bus conflict now if these were socketed a really easy thing to do would just be take them out swap them around and then see if you could then start to type and you got her keyboard back but we don't have that because these are not socketed right now so let's use the oscilloscope take a look at pin 23 I'm going to turn this on and we should see some activity on there and a good looking signal one two three let's zoom out a little bit that doesn't look like we have any activity whatsoever on here let's look at the other one one two three okay so there we go that's normal triggering of the other one this is not the one that controls the keyboard let's go over to the keyboard one and I'm going to power cycle the computer that's normal activity right there and clearly we're not getting that flashing well this is ruling out that the pla is the problem if we saw Zero activity and it was just high all the time that would kind of confirm to me that the pla on this machine maybe were bad but as I mentioned the normal pla mode on these types of longboards is the outputs get held low and I've definitely shown that on videos before and when they're held low you absolutely get a black screen because that would keep this chip enabled all the time which would definitely cause a bus conflict which would keep this computer from starting up so I'm going to socket this 6526 let's see if that fixes the machine jump cut okay well um I was getting this chip out and I don't know if this is showing up in the video footage but it looks like one of the pins is completely detached uh this one right here I haven't done anything on the top side but it looks like it had a blowout or something I think it is still connected but definitely looks sort of burned right there all right there's the chip it's out definitely something funny going on there it's hard to get the camera to focus on it but it's almost like it melted around that pin there you see that that doesn't look good oh yeah down there too and that wasn't the removal process that I was doing absolutely not I didn't uh touch the top side except for just a little bit of hot air I don't think there's any kind of damage here though I'll just clean that off with a little IPA yeah the trace is definitely still connected but just strange and here we are on the back side of the board and there's absolutely no kind of evidence of damage or anything it looks like I gotta empty that hole there oh yeah it looks a little clogged up there we go that's cleaned out but yeah whatever damage happened to that chip didn't come from the back side of the board came from something on the top side and I'm going to say that it definitely appears that no one has ever been inside this computer but that to me doesn't seem that doesn't seem right okay the new socket is installed and I have the 6526 from the zif machine in here all the test harnesses connected diagnostic cartridge it's in the machine let's turn this on and see if the machine is working all right right off the bat we have good clocks down there in the bottom right corner so I have a feeling this thing is going to be working I can hear a little bit of Buzz coming out of the Sid chip make sure the volume is turned up here all right here we go everything is testing good let's just hear those Sid tones okay yes sounds totally fine all right well that was it this computer is fixed and all we're left with is this strangely burned oh I'm putting my hand on the the Vic chip they're getting that stuff in there the strangely burned pin on here well I'm just going to get my marker and we'll put an x on here so that brings our bad part count up to what two RAM chips another two RAM chips and now 265-26s the RAM chips are easy to find replacements for but those are not easy to find replacements of all right we have the last 64c this one I wrote bad power switch and besides the fact that I think it doesn't turn on the power switch when you actually manipulate it it doesn't even feel like it's working like I don't hear the normal click so I have a feeling it's broken inside there and well maybe it's fixable so you know the drill it's time to open this up and well if you look at that that's something I haven't seen before warranty CL I don't think I've ever seen a 64 or 64c with a warranty seal like that and made in China you know what let's look at one of these other machines here where are these ones made made in USA and I think they all kind of have this same yellow sticker on the back here yep that's a USA machine as well as is this one and then the first one is also USA as well well I have to say that's kind of intriguing not so much that the sticker says made in China but a warranty sticker Phillips screws as well not the usual torques well I'm gonna have to break the seal because clearly this machine is not going to work oh these screws are in really tight as well made a little crack sound but yeah the machine is not gonna work so warranty is void oh no so I'm wondering if this is like a really late model maybe something that's got the integrated color Ram perhaps oh yeah The Shield looks different here I think it does uh it doesn't have the little trap door there for the CPU alrighty keyboard removed dirty inside but you know such is life for an old Commodore 64 with the shield removed exactly like I thought it does not have a color Ram chip so this is one of the later models very interesting it's the very first time I've seen one of these here in North America I've definitely seen these as bores that were sent in from viewers from overseas I've just never seen one actually here also take a look at this this barcode sticker that's something I can't say I've ever seen on a 64 and we know this thing has never been opened because of the warranty sticker and there is one on the back edge of the case right here as well and I'm pretty sure that I've seen these same stickers on Amigas anyways looks like the date code on these ICS is from around 1991 so uh yeah we're kind of late in the game and well that's interesting how could this thing that have never been opened have a broken capacitor that's just unusual I wonder if it was like that from when it was new I don't see how an impact could even cause that this machine doesn't have any damage or anything on here the case is in really really good shape any kind of damage would have been very obvious so that's a bit weird I'll have to fix that I guess okay first things first power switch it's not even clicking I don't know maybe that is okay best thing to do of course is get out the multimeter check for continuity so these two pins should have continuity while it's off and the same thing on this side and it does and then these two pins here won't have any continuity while it's off and you just turn it on and that should gain continuity and it does now so I guess the switch is not broken yeah this switch appears to be working properly I don't know why it doesn't feel clicky but there's no continuity there now and there is there okay switch is good other things to check the fuse that's good so no problems there that cap is clearly bad but we can try turning it on without the cap in place you know what let me just remove that cap and we'll swap it out so here's the old cap 470 microfarad at 35 volts definitely had leaked a little bit uh the one leg that was still in the board I'm going to install this cap here 330 at 50. I couldn't find uh I couldn't find the exact value but it's fine it's going to be just fine there won't be any problem it'll work without issue okay the new cap is in and it's time just to test this thing out see if it does anything hooked up to a monitor the symptom I had when I first tested this I do remember is it felt like the power switch was broken and I wasn't getting any video at all out of the video out I don't remember if the power LED was coming on maybe it was I don't quite remember this was several months ago that I did this testing so let's see what we get oh okay so we are getting video I don't know maybe the LED was bad um again I never opened the computer obviously because we didn't even have the um the broken seal there let's try connecting up the cover here and see if we have a working led oh we do it's green yeah we could tell it's later Commodore switched from Red Power LEDs to a green okay later as in the manufacturer date of this thing all right so uh RAM oh yeah okay oh wow that was hot so yet another Ram another bad Ram machine what kind of RAM is this here Texas Instruments I don't understand how I'm so much of the 4464 dram is bad let's see okay so this other chip was bad on another machine I don't know what brand that is it's got a little triangle on it and then this chip right here was bad on the first machine so we have sharp TI and this now please be mindful that this memory here this stuff right here is used on a lot of video cards especially VGA cards and stuff like that so if you have a VGA card that's got 4464 and it's not working and feel for hot RAM chips maybe whatever the Affliction is with these particular dram chips affects video cards as well alrighty new Ram is in here are the old two chips so I have the test harness connected obviously let's plug in the diagnostic cartridge I mean I'm just thinking it's gonna work right because it's kind of what's happened every time you've had bad Ram alright here we go oh look at that it came right up it's just I don't know it's unbelievable to me that's so much of this Ram is just bad three different brands as well just it seems weird to me let's see sound I think it's gonna work there it is another freaking perfectly working machine step four turn that off except for bad Ram I don't know this is just so strange how could there be so much bad Ram let's just turn it on get to the basic prompt yeah there it is looking good that brings us to a total of six bad RAM chips too bad 65 26s and of course a bad capacitor alrighty there we have it all five of these 64 C's are repaired okay well a little clarification I don't have a whole ton of extra 6526 CIA chips so the two of these machines that had those bad chips currently just have an empty socket but that means that to get those working all that needs to be done is have that chip installed but I do just want to reiterate that three of those machines had bad Ram from three different manufacturers I I boggles my mind how that's possible how the Ram is so flaky on these particular machines and I've definitely fixed several other 64 C's in the past that had the same exact problem so if you're going to be buying a 64 I still do recommend the 64c as the more reliable machine it's very likely that the thing is going to work with the caveat being the ram just put your fingers on the RAM chips see if they're feeling hot if they are well that's a really good start just swap those out and in three of these machines that got it working immediately I have an idea about why I thought the power switch was bad on the most recent one I just fixed I think when I tested it I used like a really weak power supply it wasn't my my bv3 amp 5 volt power supply I have on the bench here and maybe those RAM chips that were getting super hot when I touched them maybe they're so shorted that it actually killed the five volt rail which kept the LED from even turning on or the machine seemingly to Output no video at all so not sure about that but definitely that was all that was wrong with the computer oh and that capacitor now when I was reassembling it I meant to film it but I didn't I was putting the shield back on the RF shield and the cap I installed fit really nicely through a cutout in the board so it wouldn't be knocked over well definitely when I took that thing apart that cap that had the leg ripped out of it was laying on its side under the RF Shield so it wasn't going through that hole or that slot in the shield so I have a feeling that that cap was bad from day one when that machine was manufactured and commodore obviously by that point in the 90s maybe their quality assurance was really in the toilet especially for the 64 which was becoming a very inexpensive computer by that point so it's quite plausible that it just was like that forever and the Machine probably worked fine for who knows how long whoever used that compute here but then maybe the ram took it out of service or maybe it was out of service and then the ram died who knows so five machines they were broken now they're fixed all in one video definitely like a mini repair-a-thon something I haven't done in a long time if you enjoyed this video thumbs up would be appreciated but if you didn't you know what to do hit that subscribe button if you haven't already also I want to thank my patrons their names are scrolling up like one of the sizes screens uh they get early access to videos behind the scenes stuff things like that and if you want to become a patreon you can do so at the link in the description below and I think that's going to be it so stay healthy stay safe and I will see you next time bye [Music] thank you

Channel: Adrian's Digital Basement

Views: 111,566

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Id: EL6D5-62QeE

Length: 57min 6sec (3426 seconds)

Published: Sat Jun 17 2023