Lincoln City C64 Testing and Repairs - Part 1

hi everyone welcome back to Adrienne's digital basement on today's video we're gonna do some quick fix in of Commodore 64 boards these are the ones that desi donated to me when he gave me that Amiga 1000 out in Lincoln City Oregon so let's get right to the video [Music] so let me do a quick diagnosis of these on camera and see which ones are working and which ones aren't alright first 64 all the ones I got are 250 407 boards which are the ones I don't exactly love just because they don't have the sharpest video output what's nice about this one though is it does have a lot of socketed ICS except for the 65 26 is all these other main ones are in sockets which will make troubleshooting far easier because say one of the Rob's is bad or PLA or whatever we can easily swap that out taking a look at the RAM though all of its Fujitsu but there are two other chips that have been swapped out at some point so this board has been serviced still as the RF shield on the back so whoever did the service reinstall this and then some of the logic chips like this one here and here are the Maus branded ones which are especially prone to failure as well but at least this doesn't have the empty Ram which is pretty much a guaranteed there's gonna be at least one of those that's bad first thing I'm gonna do is I'm going to take out the CID and I'm gonna take out the PLA out of this board and I'll also take out this Vic chip as well that way if there's something wrong with the 12 volt regulator and we power this up it will not damage these chips because both the Sid and the Vic two chip on these older boards take the 12 volt input and I have had more than once that the 12 volt regulator went bad and sent something like 13 14 volts into these chips and killed both of them so I like to check that before we do anything else so I'll just pop those out alright let's test these voltages so this regulator right here is the 5 volt one 4.96 is perfect and the 12 volts right here eleven point seven so we're get a little bit under but that's totally fine as long as it's not over okay I'm just gonna do at these sockets and we're gonna reinstall the PLA and we're gonna reinstall the Vic to PLA chip in Vic to chip in plugged in the video cable let's turn this on and we're getting a black screen okay so that's you know something I guess let's quickly plug in the dead test cartridge and see if we get anything flashing on the screen nothing no flashing on the dead test cartridge on this particular computer let's do a quick check to make sure that the ICS are getting 5 volts because like the PAL board when the 12 volts is going to the Vic - you get a video signal you just don't get anything else then I am getting four point nine nine volts on the multimeter sorry you can't see that oh you know what I was about to move this out of the way and I think everyone was probably screaming at the screen I didn't even put the CPU back in dead test won't do anything without the CPU you need the PLA the CPU and the Vic - chip and all these support chips you don't need the roms you don't need the 6520 sixes you don't need the CID the rest you do need so let me reinsert the CPU in here and let's try this again part two dead test is removed oh and look at that we're kidding us picture it words this is seemingly a twerking 64 although I need to plug the diagnostic cartridge in and do a full test of that I'll do that right now diagnostic harness is connected I have the diagnostic cartridge installed set to the regular test I have speaker and a video hooked up let's power this on alright well everything looks alright except interrupts is showing bad which is implying one of these chips is bad but the CID is definitely bad on this machine it is not sounding right it's making these a lot of popping noises this could be a true 65 26 failure but other than the bad sid this machine probably will work perfectly in software and games so I'm gonna put an X on the sid chip that's really unfortunate the pla though is a good one and so is the vicked too so i'll check mark that the cpu is working as well as are these three rom chips is testing the audio right now and I do hear a little bit of it but it's popping really badly and I just faintly hear the sound I will test this hit in another machine before I declare it totally dead but in almost all certainty this Sid chip has died all right here is the next board and it's got the horrible cardboard goodbye for that one okay now this board is pretty awesome this is also a 250 407 but all of these ICS are in sockets everything it also has an r8 Vic 2 which are some of the later ones which are pretty good this stuff is all dated from 1984 there are two RAM chips in a socket the rest of the RAM chips are okey these two are Ti so I guess there's some service that's been done there's a Maus logic chip here in a socket not a great thing RF shield is installed on this so whoever did some work on here to install these sockets has obviously put that back although you know maybe this was done in the factory for you unless commodore who knows the board is really dirty it's missing the cover on the RF modulator and let's just do it did in the last one I'm going to yank out the Sid and I'm gonna I ain't got the Vic to chip see if I can get this out with the chip puller nice okay you guys know the drill quick voltage test twelve point oh five that's fine 5.02 is also fine and we're getting kind of low on four point seven eight on the five volt rail which is surprising because my power supply gives out about five point two volts before it gets to the computer so maybe there's a bad connection here on the power switch or this power connector that's quite possible I'll turn this off and on a few times it's a little bit higher now look four point eight seven volts now so that could be bad let me do some D oxide this stuff is really dirty so this is just a good chance there's just a bad connection happening here in the switch or in the power connector like this in and out a few times alright let's see if that made any difference at all four point nine two look at that we're making progress I mean that's honestly it's probably good enough right now as it is just turn this off and on or two more times yeah four point nine two that's fine that's enough voltage for this thing to work properly alright some deoxy the video socket here and let's see if we get a signal black screen black screen just gonna give the chips that are in here a little bit of a push try that again just get nothing checking the big two pins make sure none are bent there's a couple that are a little bent up so it could not might have been making bad contact so I'm just gonna straighten them up okay let's see if that made any difference none at all so we're just getting a black screen let me just feel these chips see if any of them are extra hot pick two chips is hot but that's normal means it's not hot yet but it's getting there it's just warming up let's just see if any of these things are extra hot oh yeah one of these was really hot yeah this Ram chip here whoo that's that gram chip is burning hot so that chip is bad right there I'm gonna put a little mark on there because I bet you there's something wrong with that chip I put the dead test cartridge in let's turn this on and see if I get any flashing no flashing but you know what when you have a bad chip like this it could easily be bringing down the entire address bus could be bringing down the data bus and that will prevent the dead test cartridge from working at all so I'm gonna write on here desi and I'm going to write black screen and let's move on to the next board all right this one is actually in the bottom case of a 64 top was missing and so was the cover for the vicar so let's just yank this shield off of here this machine is quite dirty inside here that looks like something something poured on top of it maybe or a lot of moisture there's sort of rust on the RF shield up on the top part but where this was laying on it there is no rust there's one motherboard out and one very dirty our shield out which is going straight into the trashcan yeah interesting there's a pencil lead in the computer case here it was actually longer and I just snapped it but this is a little thin pencil lead from a mechanical pencil okay here's the motherboard has the RF shield on the back it's the same 250 407 now this motherboard unlike that last one has a Vic - in a socket and nothing else in a socket that is extremely rude if you have a 64 like this that's that makes troubleshooting really difficult you can't even takes it out to do any kind of troubleshooting in case you might destroy it with a bad voltage regulator I'm going to take the Vic to chip out first power this on let's quickly go for the 12 volts 11.9 good we're looking fine there 5.0 4 we're good and then the main 5 volt rail 4.98 so yes all the voltage rails look perfect pop that back in and kind of like the last one we're just getting a black screen too but let me just turn this on again and I'll do the quick temperature test on the chips looking for ones that are extra hot you can use a thermal camera to do this but you can also just use your fingers so far everything is fine let's put this cartridge in which is configured for dead test ok we're getting the flash so that means at least something's going on splashing - okay really quickly I have my test bench with the ZIF socket let's pull a Ram chip off of this one that I know is good this one here let's try piggybacking this on top of the RAM chip that I think is bad which is this one right here hold it with my finger turn this on still getting a flashing two flashes as well still so a quick check of the dead test manual and two flashes says it's you 24 so that's actually this chip right here I had it on the wrong one you 24 is down there so let's put this on here and do the piggyback test again turn on the power ohayo we're getting differences we're getting some weird flashing try that again I'll use my my right hand still getting the same two flashes I don't know what those color flashes are it's probably a bad connection I think think these chips have something to do with the color RAM or something like that now that doesn't mean that that's not a bad chip that could still be a bad RAM chip it's just that doing the piggyback method just works maybe half the time at most I've had all sorts of issues like that where piggyback did not work but you can be lucky and it can work and that can help you identify very quickly if it is a bad chip and before I put this away I'm gonna pull this Vic back out again and on the other motherboard here I'm gonna pull this PLA out I'm gonna pull the CPU off this is one that just says black screen but on and on this first board the Sid was acting funny so let's pull the Sid out and I'm just gonna test all of these chips on my zip board just to double-check for sure any failure modes alright so we have the CPU we have the Vic to chip we have a PLA chip and we have the Sid this is the one that was acting very weird with that weird sounds and let's reinstall that Ram chip that I was using for piggyback testing all right and let's turn this on and see what happens we should be getting the basic screen and we are not so something here is faulty let's first swap out this Vic 2 with one that I know is working well see if that made a difference aha so this Vic too is bad this is an r8 just quickly checking to make sure all the pins are straight and they are try this one more time oh okay it's working so I just had bad contact okay good before I ruled out that that thing was bad okay so right off the bat we know the CPU is good we know this PLA is good we know the Vic too is good although it might be up dirty pins and unfortunately was the SID in one of those motherboards and it is bad getting that popping out noise again on this one too which is very very similar to the other one this one here which came in the other board which has a the exact same fault and yep the other one you heard that popping I can just hear the tones that are the different channels so just to show everyone this machine's not problematic I have a swing Sid here which is a Sid replacement not a very good one but it's all it's all I got it makes that test tone when you first turn it on the swing Sid uses a microcontroller to basically emulate the sid chip and it's a reasonable approximation but it really isn't great either and there it is that's how the diagnostic test should sound as it goes through the different waveforms on the different channels and the noise channel so yeah this this board is definitely working in the switz it sounds as it does alright I went back to the socketed board this has all the sockets those sort of one where the RAM chip was really hot I've removed the RF shield and I saw the socket there taking out that Ram chip so this is a known good Ram chip for my test board let's put that in turn the computer on and we're still getting the black screen I'm gonna pull the ROM chips out of the board sometimes on the chip spin in a long time it's kind of hard to get it out with the good chip puller the one I like here in that case a good chip lifter like this really comes in handy sometimes they're just so stuck in those sockets all right I've dead testing roms are out let's see what happens here still not working so I'm taking the Vic two out D ox at the socket I don't know if this Vic 2 is working for sure so take this one that we tested that was from the other board we're gonna put this in this socket I know that's a good chip I know there's a good CPU and no this is a good PLA I might have to take these 260 526 is out still get in the black screen oh wow so this 65 26 the legs are cut on this and they're all crooked and wobbly on here so this chip was on a board and it was D soldered and I don't know if this socket was installed we'll check in a second on the underside and this one same thing it's kind of a mess let's just leave those out I'll turn this on again and we're still getting nothing so let's just take a quick look underneath this board I'm gonna say all the sockets along the top row are original so that these two CIA chips must have come off a different board because this is definitely not reworked the two RAM chips that were originally in a socket yeah that there's a lot of flux residue so this was done after the fact and then this was the RAM chip I just put in right here the board's really in good shape either I don't see anything bad but it never hurts to do a quick continuity check along these rows of chips so let's just quickly check these rework sockets so that's good whoever did this rework originally on these sockets did a good job and there are no faults there this chip the 257 which is in a socket that socket that looks original or factory or whoever did the rework clean that up so well I can't even tell that that's not original so I wonder if that just failed when this board was being made and they put that in a socket okay so with the ZIF board here I wanted to see if this RAM chip which I just removed out of this board it's actually bad so let's pop it in this socket here let's see what happens when I turn it on oh yeah it's bad I don't have a cartridge in here it should just go straight to the blue basic screen or get nothing in fact when this is on here I don't even get the ding of the sid chip well i'm at it let's test these other two chips that are on this board that are in sockets already just make sure that these are good that one is good that one is good as well okay so back to this board I powered it up you know what that Ram chip there another okie chip is burning hot now so we got another bad chip let me do solder that okay install the socket here is the bad okie chip well I think the bad one and I have another Ram chip let's install this in my new socket there we go and let's turn it on oh and check that out let's let it run through the RAM test but it seems to be working alright Ram test has passed let me repopulate this with all of its original chips and see if this computer is now fixed I put all the original chips back in I'm on the normal diagnostic not dead test and we're not getting any picture I think first thing I'm gonna do with that test to take these ROM chips back out okay let's see what happens with the roms out of the machine and no joy still not working well let's try to get this back to a working state with the dead Test at least so okay here we go okay so we're working so the well has two chips I just pulled out with a 65 twenty-six chips so I'm gonna assume that one of those is bad so I'm going to repopulate everything except for these two chips and we're gonna turn it on and see if it goes to basic it's a lot faster than testing with the dead test okay let's see if we get into basic at this point okay we're getting basic no flashing cursor which is flying us cuz these 65 26 s are not in there so one of these 260 526 chips is bad let's just put one of them in see what happens okay that one is in black screen so at least that chip is kak just swap in the other one all right 65 26 what's gonna happen working no working oh that one's good so this chip is definitely bad big old X on there it wasn't getting hot or warm but it was keeping it from working if I plug this into that other socket I'll at least have a keyboard we can test with okay we got a flashing cursor so I'm gonna say that these ROM chips are all good so I'll put checkmarks on them I know this Vic 2 is good so I'll put a checkmark on that CPU is clearly working oh that already has a checkmark I won't put a checkmark on this 65 26 until we do the diagnostic cartridge so let's do that right now I borrowed a 65 26 off my zip machine which I know is a good ship okay moment of truth here we go turn this on there we go we got the diagnostic screen with the harness plugged in we should be getting a good test oh I actually have an O CID in here and I don't really have a working one I guess I could I'm just gonna put this up this bad sit in here it has bad sound but I bet you the paddles probably work because if we don't have that in there it will fail the diagnostic test because of the paddle signals there we go everything is okay this board is fully functional now so this is what we had bad on this one bad 65 26 this kept the computer from turning on and booting it all and too bad RAM chips that also prevented the computer from working whatsoever all right that's going to be it for part one of two parts of the Commodore 64 from Lincoln cities repair series part two which will be coming up soon I'll get to the other boards and we'll try to fix those as well but if you liked this video I'd appreciate a thumbs up if you didn't you know what to do you can hit thumbs down you can subscribe for more videos because we'll be lots more in the future and of course put your comments and your suggestions on the comment section below read every single one of them thank you very much for watching goodbye [Music]

Channel: Adrian's Digital Basement

Views: 42,074

Rating: 4.9781141 out of 5

Keywords: C64, commodore, repair, retro computer, lincoln city, commodore 64, troubleshooting, repair video, how to

Id: EfL9Yv0wZg4

Length: 21min 51sec (1311 seconds)

Published: Sun Feb 02 2020

Reddit Comments

[u/technoph0be]

You are killing it, Adrian! Can't wait to see more videos from you.