Flaky DRAM on a C64 or an Amiga 500 often means it has been connected to a dodgy (overvolting or unstable) PSU. At least in my experience that's what happens a lot ;-) DRAM is really sensitive to that and will often be the first part that kicks the bucket...
same story with the zx spectrum and especially the plethora of eastern Europe clones and their SRAM. Dodgy PSU's and crappy connectors, a recipe for failure
That Was What I Was Thinking! i Also have had A Bunch Of Old DDR2 Ram GO Bad And that is In The Era Of Capacitor gate! When I See A DDR2 Machine That Wont Boot I Check the ram 1st After Making Sure The power Supply is Coming On!
Did a lot of those in the day, we had a lot more lightening storms in the late 80s. I recall there was a pathway due to the mains sample used for the RTC that would take a number things including the ram.
Yeah, I think if the thermal paste is replaced, those metal shields can act as a pretty good heatsink. The C64 and 128 don't have fans, so it's a good way to bring heat away from the center of the board (without conducting the heat through the PCB itself). Unfortunately, in the UK, because the emmission regulations were different, they just used a cheap foil covered cardboard in the C64C machines (which just had some vent holes cut out above the hot chips). Those cardboard shields are just keeping the heat in, so they are much better removed.
According my "research" it seems that those with bad ram chips had been killed by a bad PSU. The PSU tends to drift to higher voltage. Once the 5V DC rail reaches too high voltage there is a big risk of some damage. And my friends told me the RAM chips are first to go. It explains so many C64 with a dead ram or worse a dead SID etc. Anyway very good video! As a fresh owner of a C64 I am very keen on to improve my knowladge!
@@katho8472 It's caused by dodgy PSUs. TI and Sharp DRAM is super reliable but if you connect an overvolting PSU (something the C64s are known for) the DRAM is the first thing that bites the dust...
@@pipschannel1222 Does that mean these replaced chips are also bound to fail in due course? Because obviously he didn't even test for overvolting PSU...
@@henningerhenningstone691Commodore power supplies are external to the computer, not inside like a modern computer. His is a known good one, so it shouldn't blow any chips
Again, your videos helped me get through another bad day. Thank you. Your charisma and kind tone are like electronic Valium. You're like a digital Bob Ross. :) If only the broken old thing typing this, was as easy to fix as some of the computers in your basement. I will buy you a beer with a sub to show my appreciation, when I can afford it.
@@hernancoronel Thanks. Good advice. I have health issues, but the main reason I feel like crap today, is that I gave up smoking a few days ago. Positive lifestyle choices aren't always fun.
@@EddiePedalo I've been where you are now. When my daughter asked me to promise her I would quit smoking, I did it. That was over 25 years ago. I'm here to tell you it's worth the effort, it CAN be done, and you are not alone.
melted plastic b/c of static? don't think so. probably use of an incompatible joystick. those SEGA/Genesis ones, that pull-up the control lines to 5V. if you press a key on the keyboard, that pulls one of the joystick control lines LOW, CIA pins used for the keyboard grid have to deal with more current, than they are designed for.
52:06 that little triangle logo was used by Matsushita (Panasonic) back in the day. I wonder what it is the C64 does to them that kills them as they are normally quite reliable!!
Possibly that bad cap got it’s leg removed due to ‘rage quit’ banging on the keyboard. The shielding might have pushed the side of the cap over more forcing it to detach from one of the legs.
Thanks, I really enjoy these videos. The Commodore 64 launched me on my career as a software engineer when I was in college while studying for a different degree. I bought it at K-Mart on lay-away. Good times :)
Launched mine as well. It was 1996 and I was 8 and my dad pulled his 64 out of the attic and set it up in my room after my little sister was born. Had two drives, a monitor and a printer. Tons of games to play, but I spent most of the time coming up with random programs in BASIC.
Adding a bit of yellow into your LabVIEW trace would seriously help colorblind individuals like me to see what the oscilloscope view is displaying. Thanks for the videos!
Marginal PSU's tend to kill those RAM chips first in my experiance. The last thing to go is the Sharp PLA: I even reverse polarity powered one once for a second or so and it lived.
It is funny I would have assumed other chips would go bad with the higher voltage from a failing PSU. Perhaps those RAM chips die even at 5.3v while everything else is just fine?
Back in the day, I was making a Hackintosh 128K, and I miswired the power cable to swap 5V and 12V. The RAM all fried (unfortunately, I'd already done the 512K upgrade), but everything else was fine. After changing out the RAM (again), it worked fine.
Do we actually know that? I don’t see how you can conclude that whenever RAM dies, it is the PSU but when the PLA or the kernal dies, it is something different. I have seen bad RAM chips many times, and most of the time, the PSU wasn’t outputting anything exceptional. I jave testet more than 200 PSUs and I haveseen 2 with a 5v output that was capable of causing immediate damage
@@adriansdigitalbasement Yep, it's possible: I've repaired about 10 C64c's with bad RAM exactly like this. In at least a couple of those there was also at least one bad CIA. But yeah, JUST smoked RAM is a pretty common C64c fix. I think also the 8 series (later fabs) of the cpu, vic, sid, etc etc were quite a bit more robust than the earlier 6's.
@@christianlarsen1070 Nobody is advocating that level of absolutism. I'm just reporting that as far as I've seen, 1 this failure is decently common and 2 in most I've seen it was PSU failure that brought this about. My working theory is these RAM chips want decent power and don't have quite the tolderance for over-voltage the others do. I've watched the C64 with a FLIR and the RAM chips heat up first as voltage climbs. No, not very scientific, but good enough for me and I didn't want to possibly kill the C64 to prove anything. Unless you had a scope over the PSU output at the time of failure, we'll never know if it was PSU related or not, even with a good "test" of the PSU. The power situation in the C64 is a laughable joke of poor design, - and the more epoxy bricks in the landfill the better, imho.
Haha! Success! Adrian can't throw away the RF shielding! YAYAYAYAYAYAYAYA! I just recently fixed a 64C, and I went to all the trouble of removing the rust on it with a citric acid dip, followed with a protective coating of clear coat. Of course I didn't let any clear coat get on the heatsink pads. After it was all done, I reinstalled the RF shield with new high quality thermal paste. Obviously the design is good, because even Adrian admitted the 64C computers are more reliable. It's those earlier bread bins with the cardboard RF shield that die.
@@4thdoctorwhofan966 Well.... it's all relative. Compared to the crap they had in the 80s, everything is higher quality. Including the little generic no name tube that came with my Ryzen 5 a couple of months ago, that I threw in the drawer and replaced with legit thermal paste. That generic no name stuff is what I used for the C64. Compared to the heat the Ryzen puts out, the C64 is practically ice cold.
I like to clean the thermal paste off, then install stick on copper heatsinks, then bend the shield tabs slightly to contact the top of the heatsink. This allows the heat to come off fast from the IC, then dissipate through conduction into the shield. It's a win win! I read that Bil Herd said that he wasn't sure taking off the shield and replacing it with heatsinks was the best idea due to the way the shield conducts the heat to such a large area. So I combine both - the best of both worlds!
Excellent video thanks Adrian. Having fixed a loooot of zx spectrums over here in the UK, it's so nice to see crappy Ram in commodore computers! Well done on fixing them all. Nearly every spectrum I have had bad ram at some point. I better check what my Vic 20 has got installed......
Love it! Happy to see more 64 repairs. Thankfully, you showed without a doubt what I already knew: Commodore was still making and selling 64s into the 90s in North America. Many, many arm chair historians have said that they did not make or sell them past 1989/1990 or so and that it was all European only. You have proof they did. I know in my area you could still buy the 64c in stores in the early 90s. I ran a C= BBS until 1992 and we could still go to the local Toys R Us and buy whatever C= hardware we needed. Some outlets even sold them after the bankruptcy. It truly was the computer that did not go away.
I've heard that RAM is one of the first things to go if the 5V rail goes high. It's possible that it was a PSU problem. But they are reliable and RAM is the most common fault so if you're getting only bad machines it could just be false sample bias.
That triangle logo is Matsushita (Panasonic) It seems like one of those relatively inexpensive thermal imaging cameras you plug into your phone might be useful if someone is repairing a whole load of 8-bit micros!
I can see the bad RAM in some of these machines, a computer made in 1991 is now over 30 years old, a breadbin could be as much as 40. The fact that these computers that were manufactured for under $100, only need some new RAM chips is a testament to how robust Commodore was actually making them.
Love having your repair videos running in the background as I repair my electronics! I just got one of my Odyssey 2 joysticks back up and running! Working on joystick #2 right now!
This is true! It’s like sharing a workshop with an upbeat collaborator. Keeps the vibes positive👍 I rage quit much less when dudes like Adrian are on in the background😊
I worked on many c64's, c64c's and c64g's in my days, made in China, UK and West Germany, none of them used anything but Philips screws. And all of them were warranty sealed.
The C64 can be surprisingly fragile sometimes. My kid sister once pulled a cartridge with the power on, and it damaged one bit in one register on the VIC-II, but that one bit was part of the smooth scrolling registers. For years, until I finally got around to buying a new VIC-II chip, most any game that had horizontal scrolling had extremely glitchy graphics whenever that one specific position was active...
During the early 80s, I had a Commodore 64. I was in college and used it to program in Basic. It was really cool being able to program in my bedroom. It sure beat having to go into the computer room at the university. I did that for a while. Having to stay in line. We were not struggling at all, my dad had a really good job. So he let me purchase the Commodore 64 with the screen and floppy drive. And I brought my homework home and was able to build Basic programs. it sure helped me do lot of more work not having to go into the computer room at all. I sure would love to have another commodore 64. Now that I am retired, I really don't have much money to buy such systems. :(
Great video Adrian, as usual.. Being a Commodore guy myself I especially enjoy when you repair Commodore stuff :) As I understand it there are four revisions of the short board, Rev 3, Rev 4, Rev A and Rev B and the Rev B is the revision with the video RAM integrated in the PLA. Some years ago I bought a box with 40+ short boards and out of all of the boards that I've repaired so far something like 80% have had bad DRAM. So far I've only come across one bad PLA, one had a bad CPU and the rest had a bad 6526. So, it's safe to say that failed DRAM is, at least in my experience, a pretty common fault with these boards :)
In my breadbin black screen repair video, I was expecting trouble when I saw Micron 4264 DRAM... but it turned out they were more reliable than these 4464s.
Really enjoyed the video. Nice job. So mant bad DRAM chips, but not too surprised. The only thing that was surprising is that you got a cluster of memory chips. If Comnodore only added over voltage protection on the logic supply line theae memory chips would still be alive today 😊
I actually like the design of the C64C, I had one, second hand, in the late 90s, it formerly belonged to my cousins who bought it in the late 80s I think. I know the sound chip is different, but I really like the colour and the style of the machine.
@@steven-vn9ui Yes, I think he is. I'm glad people like this exist. I thought for sure that these systems would be basically none functional by the mid-2000s. Looks like we might have C64s around for a long long time thanks to people like this.
Nearly every kid in my class had one of these back in the day, some had a msx, some an amstrad, and one fancy guy (his parents an amiga 500) i remember they where for sale till mid 90s at the discounter stores in my hometown (in the Netherlands)
Yep I remember using joystick port 2 as primary, as having a joystick plugged into port 1 could give some erratic behaviour. Don't know what the designers were thinking
hello Adrian, I still have a c64 somewhere in the house, it has a green led, also I think it was made in china, was bought around '91 in Czechoslovakia back than : - ) very cool to see you fix these machines
I bought my commodore 64C in 1987. No idea when it was produced, but it or parts were produced in Singapore, the Philippines or Malaysia. It had a warranty seal. I sold the device and my Amigas in 2007. So I cannot confirm production locations. One sure way of blowing up CIA chips is bridging the joystick forward switch with a home made foot pedal. Pressing forward and the pedal creates two parallel pads with less resistance. This blows up the CIA chip instead of the zener diode that should protect. It was an expensive learning experience for 13 year old me.
excellent video. I thoroughly enjoyed watching you go through the logical steps of diagnosing and fixing the C64s. When are you going to do a marathon on the A500. I have a dead machine here, and would learn a lot from watching you sort your way the common issues associated with the A500.
At the of Commodore quality control went out the window I bought a 128 D that long after I gave up trying to get working found out it had a functionlly idiot of a disc drive, it would work maybe once and while so I switched to IBM machines. Now some 30 years later I work on some machines as a hobby because I love the challenge of outdated tech.
I never owned or fixed a C64, learned a thing or two on repairing old machines with all the repair videos and always appreciate new ones. Please keep doing them! :)
In Germany and the Nordic contries, the Commodore 64C's were very popular and common. edit: The yellow sticker on top of the cartridge port has the production week and year of the computer printed on and written in hand..
Awesome work! Those 4464s can really be flaky. I had a non-working CoCo 2 which had 4464s that I assumed to be good. After having tried everything, I swapped the RAMs, and it freakin’ worked.
My C64 has a (broken) warranty sticker. It was a warranty replacement for a broken machine, which we bought in '88, I dunno when it was replaced, though. Could've been any time before '92 when we got the A1200. I think the reason C64Cs are so common(at least PAL ones) is 'cause game consoles(other than like the Atari 2600 etc.) weren't available here until late '87, and even when they did arrive were very costly, you could buy a C64 with datasette for the price of 2 NES/Master System cartridges. If you wanted to play video games, the C64 was by far the best cheap option available until the 16-bit machines took over.
You could always repurpose those last two hot rams to make a hot plate for soldering smd. Not totally useless. At least not until they stop heating up, or catch fire, or something.
Well the good news is that there is a FPGA replacement being developed for the 6526 CIA which was reported to be going into production prototypes in Feb this year, search for J-CIA. It seems to have passed all the tests that have been thrown at it so it looks like going forward we will at least be able to keep C64's going if the supply of 6526s runs out.
There must be a glut of commodore 64s' now, has the price gone down? Great videos, I hope younger people get into this as there's a lot to learn and it's a great way to reduce e-waste and use up all those old RAM chips!
The company for which I work makes rugged electronic equipment and we have to drop-test them and vibration test them. We have lost larger capacitors as a result of these tests, so the broken one in there could have been from a drop.
6:10 We know that Commodore manufactured C=64's even if they didn't have all the component to install. With a "trap door" they could install the missing CPU afterwards with removing the shield.
I really enjoyed that last repair because I make 256k chips at Texas Instruments from 87-95 so its very possible at some point in the manufacturing I touched those ! Since you had multiple failures across multiple manufacturers there must be some design flaw, something that age causes them to eventually short out. I love the touching for diagnostics, sometimes low tech is the easiest way to go.
The DRAM is very sensitive to over-voltage. People plug in their old machines to "test" before selling and the now dead PSU puts 12v into the 5v line and the machine is killed. The ram dies first. Depending on how long they leave it on a black screen, other chips get fried eventually. But in my experience it's dead PSUs that kill the ram.
The 8-bit hardware specialist repairs Commodore 64 with ease. It's just fun to watch you repairing C64s. I still have a C64 in the attic, which is very brown discolored. One day I will get it out and see if it still works. Of course with a new power supply! I swear! Keep up the good work Adrian!
Well this makes me feel relieved now that I have switched out the RAM in my 64C for a modern replacement. It wasn't bad - I had mainly done it as a means of "future-proofing" the machine since it's my reliable "daily driver" that I use for GEOS, gaming, and to print monthly calendars. I also had replaced my power switch which was certainly going bad - it had lost it's snap after many years of heavy usage and I didn't feel like taking it apart to service it.
I had as a kid (well still have) a breadbin with the shortboard (revB in C64G, Europe based) which at some point died (PSU gone, fuse blown). Think we got it around the end of the eighties, or 1990 probably judging from the chips. Fixing it is WIP, I replaced the ram, as I kind of expected it to be bad, but it also has the two boiling hot rom chips and I didn't have spares. Really great to see some shortboards here!
About a week ago I bought a C64 from 1992, also made in China, with the same stickers. There is no metal shield inside, only a cardboard-aluminium one. The keyboard is hold in place by clips attached to the upper part of the housing.
31:23 - I think they were making these C64c's at the same time as the Amiga 500's. The 500's had Torx screws in them, so I assume they would use the same screws on both if they had them.
Adrian fixing so many vintage machines just MAKES my DAY! 👍🙂 Also, fun fact, if you change the video playback speed to 0.5 at the end (so you can read the Patreon names more easily) Adrian sounds drunk! 😁😂🤣
In this case... black screen is a good sign for failed C64s. If that's the symptom, the problem is probably bad RAM, which is cheap and easy to replace. On the other hand, if your keyboard or clock doesn't work, the problem is probably a bad CIA, which is unobtanium.
The 4464 DRAM is usually very reliable under proper conditions. I used two of these in a CoCo (I think it was a Coco 3, but it was decades ago) and they worked just fine. If they generate a lot of heat, maybe a heat spreader on both chips might help? I see elsewhere this might be specific to the Commodore machines, especially the C64, because of the power supply "brick of death". Maybe that's what got all of these?
31:40 Since phillips screws were in the case and torque screws were securing the shield, it's also possible that this unit was disassembled previously and care wasn't taken to put them back in their original locations. 37:00 I don't know if removing the metal shield permanently is such a good idea because it not only helps protect against EMI interference, but also should help to wick away heat from the ICs, rather than acting as a blanket. This is also evidenced by the round holes that are machined into it, so as to increase airflow and heat exchange. 53:30 I'm guessing the uncontrolled ripple from the detached electrolytic couldn't have been kind to those chips... maybe accelerating the failure of the DRAM? Seems like they are being run under pretty marginal conditions even when the power supply is working perfectly... and we know what happens to those over time. 😟 I think I also read somewhere that Commodore took a stab at manufacturing DRAM themselves but threw in the towel, so to speak because they were unsuccessful to put it kindly.
Bad ram on a C64 for me, especially so many different brands and board, will always make me think some damned original Commodore power bricks failed hot and took out the chips. Same thing happened to my breadbin. Unfortunately, the event also destroyed the PLA and SID on my machine too.
Hi Adrian, i had the same problem with the ram chips. Mine were NEC branded but it seems a common failure for these c64c versions. Luckily the aren’t expensive although there are a lot fake ones for sale. Thanks for the great video! Cheers Martin
My bet is there is a PS or filtering deficiency on the data/address lines driving the RAM chips, causing failures. Its the only thing that makes sense across 3 manufacturers.
Do not remove the rf shield! 1. It's part of the original machine. 2. Rf shields are not useless! 3. Its als a giant heatsink. And i always get a heart attack when i see you run a board on this old towel..
I was more familiar with the earlier generation C64; didn't realize there was a generation towards the 90s that was remarkably different. That's pretty darn cool. Towards that time, I was focused on Tandys and IBM compatible.
Those warranty stickers are illegal in the US. The magnuson moss warranty act makes manufacturers prove that you broke something before they can void the warranty. Just opening the case is not enough.
![PASULOL รามเกียรติ์ ตอนที่ 4 นนทกพบรัก [Ramakien Ep.4: Nonthok in love]](http://i.ytimg.com/vi/tMUQgmZzf_A/mqdefault.jpg)
Flaky DRAM on a C64 or an Amiga 500 often means it has been connected to a dodgy (overvolting or unstable) PSU. At least in my experience that's what happens a lot ;-) DRAM is really sensitive to that and will often be the first part that kicks the bucket...
Basically the DRAM acted as a fuse...? :)
same story with the zx spectrum and especially the plethora of eastern Europe clones and their SRAM. Dodgy PSU's and crappy connectors, a recipe for failure
That Was What I Was Thinking! i Also have had A Bunch Of Old DDR2 Ram GO Bad And that is In The Era Of Capacitor gate! When I See A DDR2 Machine That Wont Boot I Check the ram 1st After Making Sure The power Supply is Coming On!
I was just thinking this too. With three different brands on the RAM chips. Probably something else killed them
Did a lot of those in the day, we had a lot more lightening storms in the late 80s. I recall there was a pathway due to the mains sample used for the RTC that would take a number things including the ram.
The shield also acts as the heat sink for several chips. Same with the flat 128. I always leave it and replace the thermal grease.
Yeah, I think if the thermal paste is replaced, those metal shields can act as a pretty good heatsink. The C64 and 128 don't have fans, so it's a good way to bring heat away from the center of the board (without conducting the heat through the PCB itself).
Unfortunately, in the UK, because the emmission regulations were different, they just used a cheap foil covered cardboard in the C64C machines (which just had some vent holes cut out above the hot chips). Those cardboard shields are just keeping the heat in, so they are much better removed.
According my "research" it seems that those with bad ram chips had been killed by a bad PSU. The PSU tends to drift to higher voltage. Once the 5V DC rail reaches too high voltage there is a big risk of some damage. And my friends told me the RAM chips are first to go. It explains so many C64 with a dead ram or worse a dead SID etc. Anyway very good video! As a fresh owner of a C64 I am very keen on to improve my knowladge!
I love the Commodore repair videos, takes me back to my childhood and definitely my favorite videos on this channel.
The chip with the triangular logo was made by Matsushita (Panasonic), it also has their part number (start with MN)
Correct. I have a whole sleeve of Matsushita 4164s in my stash for bread bins. Same logo.
@@vhfgamer I was under the impression that the logo in question was Mitsubishi, not Matsushita.
@@4thdoctorwhofan966 No the mitsubishi logo is more like a three pointed star. The triangle is Matsushita.
The "C", my very first computer. Got it in '88 at age 11. Theres a special place in my heart for that computer ♥ C= 64
Adrian makes an important point here, one that I was taught in electronics school in the military: Always check the power supply first.
..especially the power switch position :)
Great work, nice to see 5 C=64's which will not end up in e waste. I don't get tired of repair videos.
The 4464s have always been a common problem in the C64s, the first diagnostic step was to touch the RAM chips
Maybe it's a overvoltage or heat issue thingy that is common on those boards?
@@katho8472 It's caused by dodgy PSUs. TI and Sharp DRAM is super reliable but if you connect an overvolting PSU (something the C64s are known for) the DRAM is the first thing that bites the dust...
@@pipschannel1222 Which is good news for the other, less replaceable chips at least.
@@pipschannel1222 Does that mean these replaced chips are also bound to fail in due course? Because obviously he didn't even test for overvolting PSU...
@@henningerhenningstone691Commodore power supplies are external to the computer, not inside like a modern computer. His is a known good one, so it shouldn't blow any chips
Again, your videos helped me get through another bad day. Thank you. Your charisma and kind tone are like electronic Valium. You're like a digital Bob Ross. :) If only the broken old thing typing this, was as easy to fix as some of the computers in your basement. I will buy you a beer with a sub to show my appreciation, when I can afford it.
Research diet and feeling bad on youtube, you will be surprised. Get well soon!
@@hernancoronel Thanks. Good advice. I have health issues, but the main reason I feel like crap today, is that I gave up smoking a few days ago. Positive lifestyle choices aren't always fun.
@@EddiePedalo addictions are no fun to quit, best of luck
@@EddiePedalo stick with it. it took me 4 tries to quit, but I've been smokeless since 1987. You can do it. Best of Luck.
@@EddiePedalo I've been where you are now. When my daughter asked me to promise her I would quit smoking, I did it. That was over 25 years ago. I'm here to tell you it's worth the effort, it CAN be done, and you are not alone.
And the burned pin on the CIA is PB1, which goes straight to one of the joystick ports. Pretty clear case of static damage I'd say :D
melted plastic b/c of static? don't think so. probably use of an incompatible joystick. those SEGA/Genesis ones, that pull-up the control lines to 5V. if you press a key on the keyboard, that pulls one of the joystick control lines LOW, CIA pins used for the keyboard grid have to deal with more current, than they are designed for.
What a joy to see those 5 goodboys brought back to life! And all the SIDs are working! True treasure!
52:06 that little triangle logo was used by Matsushita (Panasonic) back in the day. I wonder what it is the C64 does to them that kills them as they are normally quite reliable!!
Possibly that bad cap got it’s leg removed due to ‘rage quit’ banging on the keyboard. The shielding might have pushed the side of the cap over more forcing it to detach from one of the legs.
Thanks, I really enjoy these videos. The Commodore 64 launched me on my career as a software engineer when I was in college while studying for a different degree. I bought it at K-Mart on lay-away. Good times :)
Launched mine as well. It was 1996 and I was 8 and my dad pulled his 64 out of the attic and set it up in my room after my little sister was born. Had two drives, a monitor and a printer. Tons of games to play, but I spent most of the time coming up with random programs in BASIC.
I got my 1541 on layaway at Zayre's in Florida!
Adding a bit of yellow into your LabVIEW trace would seriously help colorblind individuals like me to see what the oscilloscope view is displaying. Thanks for the videos!
Thanks for sharing info like this. For us non-colourblind people we easily miss things like this. Super useful to know. 😊
I'm not colorblind but I do hope he sees this.
Seconded!
Marginal PSU's tend to kill those RAM chips first in my experiance. The last thing to go is the Sharp PLA: I even reverse polarity powered one once for a second or so and it lived.
It is funny I would have assumed other chips would go bad with the higher voltage from a failing PSU. Perhaps those RAM chips die even at 5.3v while everything else is just fine?
Back in the day, I was making a Hackintosh 128K, and I miswired the power cable to swap 5V and 12V. The RAM all fried (unfortunately, I'd already done the 512K upgrade), but everything else was fine. After changing out the RAM (again), it worked fine.
Do we actually know that? I don’t see how you can conclude that whenever RAM dies, it is the PSU but when the PLA or the kernal dies, it is something different. I have seen bad RAM chips many times, and most of the time, the PSU wasn’t outputting anything exceptional. I jave testet more than 200 PSUs and I haveseen 2 with a 5v output that was capable of causing immediate damage
@@adriansdigitalbasement Yep, it's possible: I've repaired about 10 C64c's with bad RAM exactly like this. In at least a couple of those there was also at least one bad CIA. But yeah, JUST smoked RAM is a pretty common C64c fix.
I think also the 8 series (later fabs) of the cpu, vic, sid, etc etc were quite a bit more robust than the earlier 6's.
@@christianlarsen1070 Nobody is advocating that level of absolutism. I'm just reporting that as far as I've seen, 1 this failure is decently common and 2 in most I've seen it was PSU failure that brought this about.
My working theory is these RAM chips want decent power and don't have quite the tolderance for over-voltage the others do. I've watched the C64 with a FLIR and the RAM chips heat up first as voltage climbs. No, not very scientific, but good enough for me and I didn't want to possibly kill the C64 to prove anything.
Unless you had a scope over the PSU output at the time of failure, we'll never know if it was PSU related or not, even with a good "test" of the PSU. The power situation in the C64 is a laughable joke of poor design, - and the more epoxy bricks in the landfill the better, imho.
Haha! Success! Adrian can't throw away the RF shielding! YAYAYAYAYAYAYAYA!
I just recently fixed a 64C, and I went to all the trouble of removing the rust on it with a citric acid dip, followed with a protective coating of clear coat. Of course I didn't let any clear coat get on the heatsink pads. After it was all done, I reinstalled the RF shield with new high quality thermal paste.
Obviously the design is good, because even Adrian admitted the 64C computers are more reliable. It's those earlier bread bins with the cardboard RF shield that die.
I would have used low quality thermal paste. LOL
@@4thdoctorwhofan966 Well.... it's all relative. Compared to the crap they had in the 80s, everything is higher quality. Including the little generic no name tube that came with my Ryzen 5 a couple of months ago, that I threw in the drawer and replaced with legit thermal paste.
That generic no name stuff is what I used for the C64. Compared to the heat the Ryzen puts out, the C64 is practically ice cold.
I like to clean the thermal paste off, then install stick on copper heatsinks, then bend the shield tabs slightly to contact the top of the heatsink. This allows the heat to come off fast from the IC, then dissipate through conduction into the shield. It's a win win!
I read that Bil Herd said that he wasn't sure taking off the shield and replacing it with heatsinks was the best idea due to the way the shield conducts the heat to such a large area. So I combine both - the best of both worlds!
The 64C is probably my favorite one.
Excellent video thanks Adrian. Having fixed a loooot of zx spectrums over here in the UK, it's so nice to see crappy Ram in commodore computers! Well done on fixing them all.
Nearly every spectrum I have had bad ram at some point.
I better check what my Vic 20 has got installed......
Love your videos. Im from the 80s programmed these units, made lots of games in machine language love these units . Ty for the teaching of these units
I really love the way you are doing the split screen. I always appreciate it.
Love it! Happy to see more 64 repairs. Thankfully, you showed without a doubt what I already knew: Commodore was still making and selling 64s into the 90s in North America. Many, many arm chair historians have said that they did not make or sell them past 1989/1990 or so and that it was all European only. You have proof they did. I know in my area you could still buy the 64c in stores in the early 90s. I ran a C= BBS until 1992 and we could still go to the local Toys R Us and buy whatever C= hardware we needed. Some outlets even sold them after the bankruptcy. It truly was the computer that did not go away.
I've heard that RAM is one of the first things to go if the 5V rail goes high. It's possible that it was a PSU problem. But they are reliable and RAM is the most common fault so if you're getting only bad machines it could just be false sample bias.
Thank you Adrian for showing youre desoldering procedure it works very well
That triangle logo is Matsushita (Panasonic)
It seems like one of those relatively inexpensive thermal imaging cameras you plug into your phone might be useful if someone is repairing a whole load of 8-bit micros!
I can see the bad RAM in some of these machines, a computer made in 1991 is now over 30 years old, a breadbin could be as much as 40. The fact that these computers that were manufactured for under $100, only need some new RAM chips is a testament to how robust Commodore was actually making them.
Love having your repair videos running in the background as I repair my electronics! I just got one of my Odyssey 2 joysticks back up and running! Working on joystick #2 right now!
This is true! It’s like sharing a workshop with an upbeat collaborator. Keeps the vibes positive👍 I rage quit much less when dudes like Adrian are on in the background😊
I worked on many c64's, c64c's and c64g's in my days, made in China, UK and West Germany, none of them used anything but Philips screws.
And all of them were warranty sealed.
I have one ofthose version,glad to know it wasnt only mine to be "yellowed" but there are actually two versions, the white one and the "less white"
The C64 can be surprisingly fragile sometimes. My kid sister once pulled a cartridge with the power on, and it damaged one bit in one register on the VIC-II, but that one bit was part of the smooth scrolling registers. For years, until I finally got around to buying a new VIC-II chip, most any game that had horizontal scrolling had extremely glitchy graphics whenever that one specific position was active...
I am not too surprised that pulling a cartridge with power on was not a good idea though.
During the early 80s, I had a Commodore 64. I was in college and used it to program in Basic. It was really cool being able to program in my bedroom. It sure beat having to go into the computer room at the university. I did that for a while. Having to stay in line. We were not struggling at all, my dad had a really good job. So he let me purchase the Commodore 64 with the screen and floppy drive. And I brought my homework home and was able to build Basic programs. it sure helped me do lot of more work not having to go into the computer room at all. I sure would love to have another commodore 64. Now that I am retired, I really don't have much money to buy such systems. :(
Great video Adrian, as usual.. Being a Commodore guy myself I especially enjoy when you repair Commodore stuff :)
As I understand it there are four revisions of the short board, Rev 3, Rev 4, Rev A and Rev B and the Rev B is the revision with the video RAM integrated in the PLA. Some years ago I bought a box with 40+ short boards and out of all of the boards that I've repaired so far something like 80% have had bad DRAM. So far I've only come across one bad PLA, one had a bad CPU and the rest had a bad 6526. So, it's safe to say that failed DRAM is, at least in my experience, a pretty common fault with these boards :)
In my breadbin black screen repair video, I was expecting trouble when I saw Micron 4264 DRAM... but it turned out they were more reliable than these 4464s.
Really enjoying your videos. Thanks for producing this content.
Really enjoyed the video. Nice job. So mant bad DRAM chips, but not too surprised. The only thing that was surprising is that you got a cluster of memory chips. If Comnodore only added over voltage protection on the logic supply line theae memory chips would still be alive today 😊
I actually like the design of the C64C, I had one, second hand, in the late 90s, it formerly belonged to my cousins who bought it in the late 80s I think. I know the sound chip is different, but I really like the colour and the style of the machine.
13:30 - I thought I would never see Adrian's dancing again, since some time ago, in another video. Unbelievable: he did it again! 🤣
ADB saving our digital history one C64 at a time!
He's frickin awesome isn't he!
@@steven-vn9ui Yes, I think he is. I'm glad people like this exist. I thought for sure that these systems would be basically none functional by the mid-2000s. Looks like we might have C64s around for a long long time thanks to people like this.
Nearly every kid in my class had one of these back in the day, some had a msx, some an amstrad, and one fancy guy (his parents an amiga 500) i remember they where for sale till mid 90s at the discounter stores in my hometown (in the Netherlands)
Another great video of Commodore C 64 (c) repairs. The last C 64 has a PLA with the integrated colo(u)r RAM as Adrian mentioned. 🙂
Wtg, Adrian! Another great video! Thanks
We always had those exact same warranty stickers on C64s in the UK. They were usually manufactured in the UK too.
Great job again Adrian. Keep up the good work. Greetings from Steven from the Netherlands
Excellent troubleshooting as always. Surprising to see so much varied and bad RAM! Thanks for sharing and congrats on the working machines!
Aaah the C64c, i had one and many friends of mine too.
Very common here in the Netherlands in the late 80's.
Looks a lot better then the breadbin too.
Very common in Australia too, it was a cheaper visual alternative to the Amiga 500 im guessing !
Yep I remember using joystick port 2 as primary, as having a joystick plugged into port 1 could give some erratic behaviour. Don't know what the designers were thinking
This was a Great Video love the jump cuts..
hello Adrian, I still have a c64 somewhere in the house, it has a green led, also I think it was made in china, was bought around '91 in Czechoslovakia back than : - )
very cool to see you fix these machines
I bought my commodore 64C in 1987. No idea when it was produced, but it or parts were produced in Singapore, the Philippines or Malaysia. It had a warranty seal. I sold the device and my Amigas in 2007. So I cannot confirm production locations.
One sure way of blowing up CIA chips is bridging the joystick forward switch with a home made foot pedal. Pressing forward and the pedal creates two parallel pads with less resistance. This blows up the CIA chip instead of the zener diode that should protect. It was an expensive learning experience for 13 year old me.
"it was touched a very long time ago". Me too, computer. Me too lol
Love these Commodore fix videos.
excellent video. I thoroughly enjoyed watching you go through the logical steps of diagnosing and fixing the C64s. When are you going to do a marathon on the A500. I have a dead machine here, and would learn a lot from watching you sort your way the common issues associated with the A500.
i needed that 8bit dance party break today haha nice work, love to see the fixes
Nice work Adrian! Very cool to see the range of different board revisions inside the C variant case.
At the of Commodore quality control went out the window I bought a 128 D that long after I gave up trying to get working found out it had a functionlly idiot of a disc drive, it would work maybe once and while so I switched to IBM machines. Now some 30 years later I work on some machines as a hobby because I love the challenge of outdated tech.
Thanks Adrian for sharing!
I never owned or fixed a C64, learned a thing or two on repairing old machines with all the repair videos and always appreciate new ones. Please keep doing them! :)
Loved my C64. I could things with that computer that the early PC's from that time could not do
In Germany and the Nordic contries, the Commodore 64C's were very popular and common.
edit: The yellow sticker on top of the cartridge port has the production week and year of the computer printed on and written in hand..
I like your test cable setup & the plug-in diagnostic cartridge, makes this job somewhat easier!
Awesome work! Those 4464s can really be flaky. I had a non-working CoCo 2 which had 4464s that I assumed to be good. After having tried everything, I swapped the RAMs, and it freakin’ worked.
Ha! Do you remember if they got hot?
@@adriansdigitalbasement I had hot 4464s on my C64C long board. (I suspect they were victims of the PSU.)
14:32 _"which kind of implies to me at least that no one's been in this machine either"_ 🎶♫ Touched for the very first time... 🎶♫
I know that song! Like a Surgeon by Weird Al!
My C64 has a (broken) warranty sticker. It was a warranty replacement for a broken machine, which we bought in '88, I dunno when it was replaced, though. Could've been any time before '92 when we got the A1200.
I think the reason C64Cs are so common(at least PAL ones) is 'cause game consoles(other than like the Atari 2600 etc.) weren't available here until late '87, and even when they did arrive were very costly, you could buy a C64 with datasette for the price of 2 NES/Master System cartridges. If you wanted to play video games, the C64 was by far the best cheap option available until the 16-bit machines took over.
Love C64 material! Thank you!
You could always repurpose those last two hot rams to make a hot plate for soldering smd. Not totally useless. At least not until they stop heating up, or catch fire, or something.
Well the good news is that there is a FPGA replacement being developed for the 6526 CIA which was reported to be going into production prototypes in Feb this year, search for J-CIA. It seems to have passed all the tests that have been thrown at it so it looks like going forward we will at least be able to keep C64's going if the supply of 6526s runs out.
There must be a glut of commodore 64s' now, has the price gone down? Great videos, I hope younger people get into this as there's a lot to learn and it's a great way to reduce e-waste and use up all those old RAM chips!
Gah! If you ever put any of them up for sale you should let us know. Planning on getting a c64 to remember my youth!
The company for which I work makes rugged electronic equipment and we have to drop-test them and vibration test them. We have lost larger capacitors as a result of these tests, so the broken one in there could have been from a drop.
6:10 We know that Commodore manufactured C=64's even if they didn't have all the component to install. With a "trap door" they could install the missing CPU afterwards with removing the shield.
I really enjoyed that last repair because I make 256k chips at Texas Instruments from 87-95 so its very possible at some point in the manufacturing I touched those ! Since you had multiple failures across multiple manufacturers there must be some design flaw, something that age causes them to eventually short out. I love the touching for diagnostics, sometimes low tech is the easiest way to go.
The DRAM is very sensitive to over-voltage. People plug in their old machines to "test" before selling and the now dead PSU puts 12v into the 5v line and the machine is killed. The ram dies first. Depending on how long they leave it on a black screen, other chips get fried eventually. But in my experience it's dead PSUs that kill the ram.
The 8-bit hardware specialist repairs Commodore 64 with ease. It's just fun to watch you repairing C64s. I still have a C64 in the attic, which is very brown discolored. One day I will get it out and see if it still works. Of course with a new power supply! I swear! Keep up the good work Adrian!
love the show, the content, the vibe is old school tech! great job!
Awesome! Love all the commodore videos. First time I have seen a made in China C64. Hmmmm......
Triangle logo is Matsushita/Panasonic I think.
Well this makes me feel relieved now that I have switched out the RAM in my 64C for a modern replacement. It wasn't bad - I had mainly done it as a means of "future-proofing" the machine since it's my reliable "daily driver" that I use for GEOS, gaming, and to print monthly calendars. I also had replaced my power switch which was certainly going bad - it had lost it's snap after many years of heavy usage and I didn't feel like taking it apart to service it.
I had as a kid (well still have) a breadbin with the shortboard (revB in C64G, Europe based) which at some point died (PSU gone, fuse blown). Think we got it around the end of the eighties, or 1990 probably judging from the chips. Fixing it is WIP, I replaced the ram, as I kind of expected it to be bad, but it also has the two boiling hot rom chips and I didn't have spares. Really great to see some shortboards here!
52:04
_"I don't know what brand..."_
Matsushita Electric, a.k.a. Panasonic.
About a week ago I bought a C64 from 1992, also made in China, with the same stickers. There is no metal shield inside, only a cardboard-aluminium one. The keyboard is hold in place by clips attached to the upper part of the housing.
The 64C case I bought from eBay had a warranty seal sticker on it like that.
Very happy to see some Commodore Videos again! Great repairathon too! -Mark.
Think i have watched you work on these so much i could almost do it myself, great work as always, you make it look easy lol
31:23 - I think they were making these C64c's at the same time as the Amiga 500's. The 500's had Torx screws in them, so I assume they would use the same screws on both if they had them.
5!? I've yet to find one 64c least you got them all working again
y eah we need the dance party, that was just the Donkey Kong game music
Adrian fixing so many vintage machines just MAKES my DAY! 👍🙂 Also, fun fact, if you change the video playback speed to 0.5 at the end (so you can read the Patreon names more easily) Adrian sounds drunk! 😁😂🤣
LOL!!!!!!!!!!!! #drunk
In this case... black screen is a good sign for failed C64s. If that's the symptom, the problem is probably bad RAM, which is cheap and easy to replace. On the other hand, if your keyboard or clock doesn't work, the problem is probably a bad CIA, which is unobtanium.
The 4464 DRAM is usually very reliable under proper conditions. I used two of these in a CoCo (I think it was a Coco 3, but it was decades ago) and they worked just fine.
If they generate a lot of heat, maybe a heat spreader on both chips might help? I see elsewhere this might be specific to the Commodore machines, especially the C64, because of the power supply "brick of death". Maybe that's what got all of these?
I was thinking the same thing. Maybe something in the c64 design just drove something on these chips out of spec just enough to kill them.
Fingering chips?
Is that sanitary for an 8-bit party? Shouldn't you wash your hands first? 🤣
Smell his fingers.
31:40 Since phillips screws were in the case and torque screws were securing the shield, it's also possible that this unit was disassembled previously and care wasn't taken to put them back in their original locations.
37:00 I don't know if removing the metal shield permanently is such a good idea because it not only helps protect against EMI interference, but also should help to wick away heat from the ICs, rather than acting as a blanket. This is also evidenced by the round holes that are machined into it, so as to increase airflow and heat exchange.
53:30 I'm guessing the uncontrolled ripple from the detached electrolytic couldn't have been kind to those chips... maybe accelerating the failure of the DRAM? Seems like they are being run under pretty marginal conditions even when the power supply is working perfectly... and we know what happens to those over time. 😟 I think I also read somewhere that Commodore took a stab at manufacturing DRAM themselves but threw in the towel, so to speak because they were unsuccessful to put it kindly.
My favorite content on this channel. There can't ever be too many C64 repairathons.
Bad ram on a C64 for me, especially so many different brands and board, will always make me think some damned original Commodore power bricks failed hot and took out the chips. Same thing happened to my breadbin. Unfortunately, the event also destroyed the PLA and SID on my machine too.
Hi Adrian, i had the same problem with the ram chips. Mine were NEC branded but it seems a common failure for these c64c versions. Luckily the aren’t expensive although there are a lot fake ones for sale. Thanks for the great video! Cheers Martin
My bet is there is a PS or filtering deficiency on the data/address lines driving the RAM chips, causing failures. Its the only thing that makes sense across 3 manufacturers.
Do not remove the rf shield! 1. It's part of the original machine. 2. Rf shields are not useless! 3. Its als a giant heatsink.
And i always get a heart attack when i see you run a board on this old towel..
I was more familiar with the earlier generation C64; didn't realize there was a generation towards the 90s that was remarkably different. That's pretty darn cool. Towards that time, I was focused on Tandys and IBM compatible.
Great repairs , showing your experience with the machine!
Those warranty stickers are illegal in the US. The magnuson moss warranty act makes manufacturers prove that you broke something before they can void the warranty. Just opening the case is not enough.
Good to know!