Amiga 4000 Repair Part 1: Recapping and RAM issues galore!

well hello everyone and welcome back to adrian's digital basement on today's video i'm going to try to repair this amiga 4000 let's get right to it [Music] this amigo 4000 was donated to the channel by george if you remember my pet rescue series the pet 2001 that machine was also donated by the same george who lived out near bend oregon thank you very much george for donating this well unfortunately this 4000 does not work or at least it didn't when i first tested it when i got it from george so it's now time to work on this now as a disclaimer i have opened this machine up it had a video toaster inside which i've removed i've removed all of the cards actually and i did also remove the hard drives and i have some screws and stuff here so i know there's nothing loose inside this machine there is nothing that looks dangerous to power it up on this is an amiga 4000 40 which means instead of having a 68030 cpu card in it it has the o40 card from my understanding you could buy this computer with either cpu configuration and the cpu was not built into the motherboard so if you have an o41 like this which says slash o 40 here on the sticker that means that if i pull that card out there is no cpu at all the computer clearly won't work like i had just mentioned this computer is in really good shape except it's just dirty but that's nothing that a little elbow grease won't fix so the amiga 4000 along with the amiga 600 and 1200 are notorious for leaking caps kind of like the macintoshes that i just did on the repair-a-thon so there's a good chance that that is probably one of the faults in this machine now i did briefly power this on when i first got it and i wrote on the top with a piece of tape that it was flashing a yellow screen so let's power on the monitor here and let's see if this has still the same symptoms i would say it's been what like over a year since i've had this machine so maybe it's gotten worse i don't know we'll find out in a second make sure the monitor is on rgb which it is it's plugged in through the amiga video cable on the back and here we go let's power this on okay we're getting the green screen immediately and it's flashing so it's good in that there's a video signal bad in that it's flashing i notice there's no power led at all so that's a bit strange oh sorry for the background noise my ac just turned on let's turn on the computer again same exact problem splashing with a green screen so i assume it's some type of an error like maybe it's a ram air or something else and then the computer is resetting itself let me pop off the cover now i never reinstall the screws because i knew i would be working on this computer again so that's easy to remove so there's the inside of the machine and like i mentioned i already removed the cards that were in here now one thing you may notice right off the bat and people might be like oh dear this machine has a battery still now when i opened this when i first got it i inspected and i didn't witness any leaking from the battery and i am quite sure that george the previous owner's machine had had this replaced at some point so i'll definitely be taking this out and replacing this with a new battery and not another rechargeable one like this i'll put in a cr2032 with a diode but this board of course has lots of these surface mount electrolytic caps all around and on the cpu card which is down behind this riser card and none of them actually look leaky well they probably are leaking but i don't see a lot of corrosion this is nothing like those max i was just working on where there was substantial damage on the boards from the leaking caps i can see there's definitely a little bit of corrosion evidence right here around the battery but it generally doesn't look too bad now i did a quick google for flashing green screen and here we are on the english amiga board and it definitely seems like people are saying that the problem is bad chip memory as that would cause the green flashing and taking a look at the ram here there are actually five slots one two three four and five and it's this slot back here that contains the chip memory and supposedly the green flashing means a chip memory problem now one thing that scares me to death about these sim sockets is i know they are notoriously easy to break these little plastic clips that are on both sides of each of the sims are very easy to snap and once you break those there is really nothing to hold this memory in and of course you can't get a working computer without working ram so if these break off there's a good chance i'm going to have to replace these sim sockets all together and i really really don't want to do that so i think as a first step i'm just going to remove this motherboard from this case so i can work on it a little more easily out of the case [Music] one thing i don't like about the amiga 4000 it's relatively serviceable but the problem is you can't take all the screws of the motherboard out without taking this drive chassis out that's holding the floppy and to get that off you have to take the front cover off and to get the front cover off it's kind of hard there are little clips all around the front here which require you to carefully bend them and squeeze them to try to get this stupid front panel off it's all just not very easy at least from my understanding if there's a trick that you know please let me know in the comments section so the next time i work on this 4000 i won't have such a hard time well that explains why the power led wasn't working none of these front switches were actually plugged in you route them through a small hole in the front of the case right here and uh yeah i guess this machine has been serviced before to change that battery last time and those were never reconnected so that's why i saw no power led [Music] okay so here's the 4000 motherboard and here is the 68040 accelerator board now like i had mentioned this looked like there wasn't too much corrosion around this varda battery i mean it's a varda so you know what that means really right let's flip this over and see what we see uh-oh that does not look good that is definitely definitely battery leakage now i can say that this battery does appear that it was changed i see evidence of rework on the battery pins there but i definitely see a good amount of corrosion on here it's not to say this computer is ruined from this but this is not good i'm going to have to clean this off where i'll use some vinegar to start with on this battery because it's very basic what leaks out of these nikoi batteries is a base and you need a vinegar to neutralize it so i'm going to pour a ton of vinegar on this thing and we'll let it soak and see if we can at least get rid of some of this fluff and corrosion ah good the air conditioning finally shut off okay so in this little container here which says biohazard i happen to have some regular white vinegar so i'm just gonna put a towel under it and we'll pour some on and just let this work at it this looks like it's someone has attempted to clean this already so i'm not seeing a lot of reaction when you have a lot of the base from the leaky battery you'll get fizzing you know which is what you get with a vinegar and a base it's definitely some corrosion in here i see some traces that do not look great so some barge wires are probably in this motherboard's future so i'm just going to spread this around and then i'm going to let it sit now the vinegar is just pulled up on here i'm going to take my tweezers and i'm just going to scrape the solder mask a little bit because there are probably areas right here where the corrosion has made its way underneath the solder mask so it's corroded anyway so i might as well just release it and allow the vinegar to you know make contact with the copper and then i'll what i'll do is i'll reapply some kind of a coating on here i just don't want the the leaky nicad electrolyte to be lingering around underneath the solder mask to kind of continue to corrode away [Music] all right well i'm going to cut away the source of the problem which is this bad battery right use my little snips here these these side cutters and just cut away at the battery to get it out of here there's this battery made in germany i would say that this one doesn't look leaky because i don't see any evidence of leaking on these metal pads here so this battery probably didn't cause this leakage this was probably leakage from the previous battery and whoever cleaned it up probably replaced it and just didn't get all the corrosion so i'm going to pour some of my vinegar on this side of the board see little spots where the traces look bad right here oh but once you remove the solder mask it looked okay so so really this is my first time trying to do any repair work on an amiga 4000 and while we let this vinegar soak in i'm checking around the capacitors here and it doesn't look that bad i could just i don't see a lot of evidence of the leaky caps oh i think these are a little crusty over here so we got a little bit of leakage in this area of the board yep it could be just dirty i need to clean this board it's all pretty dusty but yeah i'd say what's on this ic and everything around here is corroded all right i want to try to take this ram out of here and the ram is pretty much this double stacked stuff and it looks like it's barely in the sockets so these little clips here and here you have to bend them to the sides to get the memory out and these are what break so you have to just be so so careful and only bend it as much well i thought that broke it didn't and maybe there's some corrosion on the pads which is why they're not working or why we're getting that flashing but i'm going to try to take all this out so i can give this motherboard a good wash okay so far two out without breaking okay there we go that one's out keep your fingers crossed everyone there we go next one out nope we're looking good these aren't snapped except to be so careful and this last one is the chip memory which is what's causing that green flashing supposedly it could also be a bad trace could be a bad capacitor could be lots of things right carefully there we go and there is the two megabyte chip memory from my understanding that's how big this is okay i'm gonna remove these two kickstart rom says kickstart version 40.68 amiga 4000 just because these labels are ready to fall off i am going to write 176 here and 175 there that's the silk screen part number right there for the motherboard so i will know exactly how to put these back in when i go to reassemble oh these chips are really stuck so there are the two chips out wow that's that was crazy to get these out they aren't broken or anything well i want to watch the board at this point uh some people do recommend taking out any of the socketed ics so that there's this large one here this is chipped as well everything else is soldered on but you know what i am going to wash this as is and i'm gonna do it in the sink with soap and water and we're gonna put this thing into the water [Music] so the motherboard is soaking in soapy water i think i want to try to test this ram out this is all the memory i took out i have a motherboard to test this on and it's not an amiga 4000 it is a pentium test bench i have i took this out of some random computer ages ago i think the case was wrecked or whatever there's a power supply under there there's the old motherboard mounting plate i have a compact flash or i'm sorry rather an sd card to ide adapter here and does have a 3d printed back plate so i can just let this sort of sit on top of here so i'd say that this ram should at least work in here maybe not that chip memory stick but at least these individual ones unlike the amiga the memory slots on this have metal clips on them so that you have no issue with a risk of breaking it by taking the memory in and out all right one amiga ram sim is in this machine i also have a postcard connected the postcard if you're familiar as an isa or pci slot and it will show the bios postcode very helpful in diagnosing a pc if you don't get initialization on the ram or on the vga so you have no image but you're trying to figure out what the error is you can use a postcard it also has a little thing to plug a speaker in since this motherboard has no speaker there is one on this card here so i can hear any beep codes and let me to the power and see what happens okay so we're getting beep code and i think this is upside down right now so we are getting a 13. so let me try installing a second memory module here so so i'm going to install a second memory module i really don't remember if you need to on the 440 bx motherboard or not and it looks like you need two because now it's booting up normally the codes and we have picture so we got eight megs of ram that's with two of these so the amiga had 16 megs of ram in it not including the chip memory so i'm just going to install the other two memory modules and then i'll run memtest86 and we'll just validate that at least the fast ram on the amiga is all good and has no errors so that's interesting when i power it up with all the memory and i get a white screen well that was a definitely a bust with the original ram i had in this machine which is stuff i just found in a box computer works fine and yet with this amiga memory not so much okay so that was a fail i cannot test the amiga memory on a pentium motherboard okay it's time to take the motherboard out of the soapy water let's say it's been soaking for long enough i need to drain the sink and then give this motherboard a good rinse to get all of the detergent and soap off of it motherboard is looking very nice and clean but clearly it's all wet and i want to give it a nice dry before i do any work like i'm not going to try to power it up like this obviously so i'm going to hit the motherboard with the duster this was sent in on a mail call by a very nice viewer i absolutely love this thing it's like a vacuum cleaner motor with a vacuum cleaner nozzle and it's esd safe and it's great for blowing all of the water out of all the nooks and crannies of motherboards like this it really accelerates the drying and i don't need to use alcohol so i'm not breathing in those toxic fumes this thing is just air so looking at the top side it's better in this area post-cleaning so this is obviously the real-time clock chip here it's labeled ricoh i don't know what this little ic does here but definitely a lot of corrosion around its legs but hopefully it's still connected and still working i'm going to try to trace out some of these traces here they seem to head up to this resistor pack right there and make sure it's good and of course we'll be changing all these capacitors and the back of the board is looking way better now you'll see some scratch marks here that's from my tweezers where i was trying to scratch the solder mask off of these these traces but all that nicad juice had leaked on the back here it was kind of dull so most of this is all nice and shiny again in all the other areas but i'm pretty pleased with how this turned out i think this is good this shouldn't get any worse as time goes on so before i remove any of these caps i'm going to use my phone to take pictures close up of the board of the orientation of the caps and that way i can quickly reference it without having to check on some data sheet to see exactly where the new caps are going to go back on [Music] [Music] [Music] [Music] [Music] [Music] okay all the caps are off the pads are cleaned i even cleaned up the battery connector here i was able to get the solder out but you can see here these capacitors here and here things are looking good and over here by the audio jacks all of this cleaned up really well there are what six capacitors there none of the pads are screwed up or damaged there's a cap here that came off very nicely over by the power connector here there's a cap there and two there and those pads look great there's a cap right here and that one is good and one thing that's really funny is i think this is a mistake see this little thing that's stuck on the board here this looks like a pin socket underneath this crystal here is one of are these pin sockets so see i can take this crystal off the motherboard and it doesn't look like there's a socket there but there are there are little tiny metal pin sockets so basically the hole is slightly bigger on the motherboard and then things like this can plug straight in well it looks like to me they accidentally dropped one of those pin sockets on the motherboard right there and it got sort of stuck down with the soldering so i'm gonna remove that because there's no way that that's supposed to be sitting right there and this capacitor here these are the pads that are the most sort of gunked up but it's actually not a big deal because it didn't really get too deep so i can just scrape the top layer off this is a pick right here and that will be perfect for soldering on the new capacitors i'm going to give the ram sockets a good scrub this is 99 alcohol here and i am just going to really give this a good old scrub with this toothbrush right in there hopefully if there was any kind of corrosion or issues inside there causing that ram not to work that should help and i'm going to look anywhere else on the board where there might be a little bit of sort of blue looking corrosion on any pins on ics and i'm going to scrub that off with the ipa and the toothbrush this is the mess of all the capacitors the pins the base and even the solder wick that i used to clean up this board i did also take the capacitors off of the accelerator and that is all of the crap that this board had on it good riddance to you this is all going into the trash bye okay it's been a few days and i'm sure that these things are totally dry so i'll do the recapping and then i can test them out for the recapping i bought some recap kits from console 5. i'll put a link in the description to these i've never used them from these guys before so i don't know how good they are but taking a look at the capacitors they sent me they seem to be panasonic brand which i'm going to say is a thumbs up they're pretty good it does come with two of the electrolytics which i've actually already changed these are the two that were on the motherboard already so one is here and one is here and just for fun let's take a look at what these are on the esr meter so they're 16 volts 470 micro farad so let's just pop them into the esr meter so 413 microfarad at 0.19 ohms and actually that's at one kilohertz let's change the frequency these are probably used on like the 12 volt or 5 volt rail which means the frequency should probably be set to 100 hertz so we'll test that again 440 and 0.2 ohms so i'd say that that capacitor is actually totally good and this other one 443 microfarads at 0.2 ohms as well so both of these are definitely good but hey i have these capacitors here so i might as well change them right okay so i have the photographs that i took of the boards here and i'm going to start with the processor board i've called this accelerator board a couple times this video i apologize since there is no processor on the motherboard this is actually just a cpu card and not an accelerator but if there were one on the motherboard this would be an accelerator right so all the pads are nice and they're ready to accept the capacitors let me begin the soldering [Music] [Applause] so [Music] okay other than the ipad problems the recapping was uneventful everything went on quite easily no issues with pads not taking the solder of course i used lots of flux from my flex pen on both the pads and on the bottoms of the capacitors so it was all pretty simple what i'm going to do now is i'm going to tone out those traces on the bottom and a couple on the top here that don't look good and edit add any badges that i need [Music] okay so i've toned up pretty much everything i can here and right now it seems to be all good when i'm done i will coat it with this clear lacquer but i won't do that yet until i troubleshoot this board and make sure it works because if there is a fault that i missed over in this area and i put lacquer on there it will be harder for me to fix so i'm just going to leave it as is and do some testing of of this board like it is here [Music] okay i carefully inserted the two megabytes of chip ram and the two roms and i used the deoxide of course on those so especially with the roms they were so hard to get out so the deoxit makes it easier to take those out if i need to i also apply deoxide inside the processor card connector which i'm going to carefully reconnect right now there are little black plastic standoffs that you basically screw into to hold the processor card in there's one on both sides of there there was one more that i took out but there originally were four and only two of them are left so i will screw those back in but that's after we do the testing okay so i'm ready to go for testing 1084 is connected and powered on power supply is connected to the motherboard there is power into it processor card is installed two megabytes of chip ram is on the board the original chip ram that was showing is bad so if i have the exact same problem i think the next thing we'll do is to change out the chip ram and then i think i'm good i don't think i need fast ram on the amiga 4000 i think chip ram should be enough to at least get it to show the startup screen oh yeah and the roms are installed underneath there so i'm crossing my fingers that nothing's gonna smoke on this we're gonna watch this together here we go oh no it's still green okay well that is at least the same as it was so it's not worse i think that means that the processor is running and the roms are running because that's the green screen so i think the next thing to try will be to switch out the chip ram i think what i have not done is test to see if the voltage rails are correct so let's just give this a quick check on the power supply 11.95 that would be the 12 volt rail clearly that is working fine and the 5 volt rail is the important one 5.009 okay so we're looking good on the two voltage rails okay let me very carefully pop out this chip memory there it is so i know this memory totally works and it is 60 nanoseconds which appears to be a little faster this is 70. and let me carefully do the insertion i feel very uneasy putting memory in and out of these sim sockets but what can i do right okay the memory is in and let's see what happens i'm gonna leave it set for two megabytes and we'll turn this on oh wait look at that gray screen come on please it's probably looking for the hard drive maybe maybe let's see what happens it's very possible that this memory is just not compatible and without working chip memory you're not going to get a display of any kind so this doesn't seem quite right it shouldn't take oh whoa oh my look at that it's working oh boy all right the original floppy drive from this machine is connected which may not work but i have amiga workbench 3.0 here we'll try booting this even though the roms are workbench 3.1 the 3.0 floppy should work well i need to plug a mouse in all right i have a tank mouse plugged in and let's power on the power supply again i guess i have the floppy cable on backwards let's power this on well the floppy drive is accessing so that's a good sign all right oh look at this everyone so we're only seeing two megabytes of memory so i assume to go to eight megabytes maybe there's a mod you have to do or this is not the right memory but it is working at two megabytes even though it's an eight megabyte stick which is fine with me the computer on the other hand so far seems to be working fine i mean we're just in workbench here not stress testing it but this is a good sign that it's actually working so i didn't really want to break up the four sims that were in the pentium by putting one for chip ram so i actually tried this random sim i had that had four chips on it in that socket and sure enough it works we're getting the same two megabytes of chip ram and that's perfect because this was a one-off chip i don't know where it came from and the fact is it's working so all the better now as for the rest of the ram i have this memory here which i found in a box i'm going to try this stuff in this machine and see if it works i don't actually know the size of this but it's less tall than that tall memory that was in here and i didn't like how it was barely fitting in these sockets so hopefully this memory fits in here a little bit better and it actually works in here now the question is can you install one memory module into the amiga 4000 this is the fast memory i don't know so i'm going to install two of these just because that's sort of like what you have to do in the pc and the memory does go in there okay this is 60 nanosecond ram incidentally so that should be fast enough i am just being very careful with these stupid ass clips here there's one come on there we go well i wait for this to boot there is a jumper right here which says sim size and it's basically says 256 times 32 or 1 megabytes times 32 so one of those is obviously larger it's currently set to the larger of the two settings so i assume this machine had a maxed out memory configuration originally so let's see if this works at all and yes everything seems to be working we have two megs of graphics memory or chip memory and eight megabytes of other memory which is fast memory so i should be able to get this thing up to 16 megabytes if i install those other two sims in here okay all the memory is installed nothing broke on the clips but these clips on the right they've been sort of bent over to one side for so long with that other memory that was installed in here that even when i push them into the right position they sort of spring back over to the side so hopefully this all holds together i just heard a little snap sound from this ram area here so i'm going to take a closer look make sure nothing broke everything looks okay the computer's booting right now so let's see what we got yep 16 megabytes of ram 16 megs 2 megs of chip ram so thumbs up to a fully maxed out memory configuration on the amiga 4000 so i want to show you guys close up what's happening with these little clips so i'm lifting up on the clip and moving it over and it just kind of moves back off the sim so it's barely holding the sim so i'm going to take a little bit of folded up paper and i'm going to try to like wedge it in between the clip and the side of the sim socket the plastic on the sim socket is stronger right here so this just helps keep that clip pushed this way onto the memory module all right so i've been playing around with this machine a little bit and not all is well with it yeah it's kind of working oh maybe it's actually going to work right now sometimes when i power on the machine let me power cycle it i get a yellow screen and it's not yellow right now so it's seemingly working and if i power cycle it enough times i'll get a flashing yellow screen which is incidentally that's what i saw when i first tested this machine i written on it yellow flashing screen and then when we went to test this later we had the flashing green and it seemed like it was definitely the bad chip memory which changing this out made it work but now i occasionally get a flashing yellow screen but it's intermittent and the machine appears to work when you don't get that power on flashing screen it actually boots up normally so i'm booting sysinfo here which will show us a little bit of information about this machine and i noticed there's a problem in this program too that maybe something's bad let's let's look at that well i hit the speed button to check that in the computer has actually locked up so this machine is definitely an unhappy machine but here's what i wanted to mention it says clock not found that's got to be an issue now i don't have a battery connected to the machine right now but that's fine because even when the battery is disconnected and you power up the amiga you should have a clock because the clock chip oh the computer just rebooted itself the clock ship is right here and five volts is being supplied to the rechargeable battery which of course is not installed but the computer should see a clock so there's definitely there's some kind of damage here that has caused the clock not to be working and i guess it's maybe causing this instability although this could still easily be this fast ram maybe this ram i installed is not completely compatible with this computer it's totally possible so i think at the minimum it's time to investigate what's going on with the clock here and see if i can get this working incidentally you notice i'm using an external floppy drive that has a go take in it and there's a nice jumper right here on the amiga 4000 unless you select between the internal floppy drive or the external drive to be df0 which is the first floppy drive on the amiga [Music] okay so i'm trying to troubleshoot the clock issue so you're booting up a workbench disk here if you try to even read the clock or even reset the clock it just says clock not found i also ran amiga assist test or immediate test kit i think it's called it's an open source diagnostic suite it also reports it can't find the clock this i see here is the clock chip and it's getting power i've checked all the traces everything looks good but it connects to the address bus of the computer through this ic right here which is right next to the battery and all that corrosion now i'm looking at the address lines that go into this chip it's a 74 ls 174 and i see when i try to read the clock i see bursts of activity on the cpu side on the the computer side of things but the pins that go to this chip they just sit there at high here's the 74 hct 174 that's the chip that connects u178 so this is the clock chip over here on the right and it's connected to the computer's bus and i see activity on the left side of this chip but i see absolutely nothing on the right side there's a clock input to the 174 that's called latch address and that clock signal looks totally good as well now i think there's really two possibilities either this clock chip itself is bad u178 or this hct 174 is bad now i'm not totally sure how this circuit is supposed to work the clock chip has four data lines and four address lines the four data lines are connected directly to the same data bus connections as the rom chips which are clearly working because the computer is booting up properly so those signals are getting through and i can look in the scope and i can see those data signals but on the other hand the address lines aren't getting any signals at all they are just stuck high this really feels like to me like this 174 here is bad this 174 ic is quite crusty so i think my best bet is probably just to remove this from the motherboard see if i can find another surface mount chip to try to install well i'm going to end this video here i know everyone just loves it when the videos are super long but i have to cut them down to some amount of length and there will be another part at least so if you like this video so far i'd appreciate a thumbs up but if you didn't you know what to do you can hit that thumbs down button hit that subscribe button subscribe to my channel it really helps and of course hit that little bell icon if you want to get notified when i post new videos and then you put your comments and your suggestions down in the comment section below i really appreciate it when you do comment and that's gonna be it stay healthy stay safe and i'll see you next time goodbye you

Channel: Adrian's Digital Basement

Views: 113,159

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Id: gkCDdSdSNu0

Length: 39min 16sec (2356 seconds)

Published: Sat Jun 20 2020