Five bad Commodore 64s. One hour. All fixed!
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- Опубликовано: 28 сен 2024
- Even though we have five broken Commodore 64C machines on the bench today, I still say this specific type of C64 is the most reliable of all. (Running on original hardware.) Let's see if I can get all five fixed in one video!
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Hakko FR301 Desoldering Iron:
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Magnetic Screw Holder:
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Universal ZIP sockets: (clones, used on my ZIF-64 test machine)
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RetroTink 2X Upconverter: (to hook up something like a C64 to HDMI)
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Plato (Clone) Side Cutters: (order five)
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--- Links
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--- Instructional videos
My video on damage-free chip removal:
• How to remove chips wi...
--- Music
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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
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 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.
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
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.
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.
13:30 - I thought I would never see Adrian's dancing again, since some time ago, in another video. Unbelievable: he did it again! 🤣
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.
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.
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 :)
Excellent troubleshooting as always. Surprising to see so much varied and bad RAM! Thanks for sharing and congrats on the working machines!
Nice work Adrian! Very cool to see the range of different board revisions inside the C variant case.
Love these Commodore fix videos.
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. :(
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.
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
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.
I love the Commodore repair videos, takes me back to my childhood and definitely my favorite videos on this channel.
Love C64 material! Thank you!
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!
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.)
My favorite content on this channel. There can't ever be too many C64 repairathons.
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.
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
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.
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"
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.
Come for the broken Commodore 64s, stay for Adrian's 8-bit Dance Party. 😁
The 64C case I bought from eBay had a warranty seal sticker on it like that.
I love troubleshooting and love seeing how your brain diagnoses problems and reassesses when your initial assessments are incorrect. Keep it up!
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......
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!
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.
Awesome! Love all the commodore videos. First time I have seen a made in China C64. Hmmmm......
love the show, the content, the vibe is old school tech! great job!
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.
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)
I wonder if Commodore was doing something out-of-spec with the RAM they used. Weird that the C64s have bad RAM at a rate way out of scale with other devices from the era. Like maybe something with the always-sus power supply.
exactly, the 4164 memory can safely drive a load of 2 TTL gates, not drive the entire bus as commodore does, This will cause gate degradation over time, as well as degradation of the gates as they age. Ram running hot at failure show a breakdown of the substrate insulation layer that increases current consumption. Give those chips another 10 years of aging, and they will go to dead short Vcc to Vss
@@steveb3885 I consider 2 TTL gates is quite a bit; the data sheet of the SN7400 for example lists 14mA as input current. The chips on the C64 mainboard are NMOS, i.e. MOSFET based and as a result pull waayyy less current from the bus than TTL chips.
@@danielmantione That is the actual spec for the 4116 and 4164 directly off the data sheet
@@steveb3885 Yes, but it's quite difficult to translate that to the C64 bus. However, I would expect that all chips together have a lower DC load than 2 TTL chips and it is mainly the parasitic capacity of the bus that causes load on the chips during transitions. It's quite difficult to reason from data sheets on this.
@@danielmantione it's actually quite easy. Just add up the load of every ic that does not tristate on the bus, but I do agree, the load capacitance would be extremely high the way the board is designed. They learned from the 64 as the 128 has no where near the problems with dead memory
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.
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.
Thank you Adrian for showing youre desoldering procedure it works very well
Is it possible that the Commodore design drives those RAM chips beyond their specs? Maybe it's eventually killing them, regardless of who manufactured them.
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!
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.
If so many brands of RAM fail, I'm thinking there must be a flaw in the circuit design that occasionally causes the chips to get fried.
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.
Maybe they all suffered from a faulty power supply where the 5V went too high and they where the first casualties ?
Really enjoying your videos. Thanks for producing this content.
that is crazy I could see maybe one brand of ram but more then one brand !
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.
First time I see a C64C with the combo metal shield / short board inside, I thought it was only for the Breadbin model.
I got two C64C and they both don't have that metal shield but a piece of cardboard covered by a foil of aluminum as heatsink. Their only difference is the power LED color (one is green, the other is orange).
They should belong to the latest ultra cost-cutting batches assembled around 1990-1991, according to a website that keep a reference of their serial numbers I've checked years ago.
The triangle symbol might be Hitachi?
And a major cause of bad RAM I've read about is bad power bricks.
I am wondering if maybe the C64 is rough on the RAM? Power not clean enough? It's makes me think that because you have multiple manufacturers. Looking forward to Coleco Adam content.
Woohoo! A C64 repair video!!!
The fact that they are burning out different brands of ram make me wonder if there is some sort of cheap fault in how the 64C's are made that is overworking ram to the point of a high failure rate.
Today March 2024 I googled the 6526 and there is a replacement called J-CIA64. The cost is rather steep and probably easier to find a dead C64 and salvage the chip from it.
The RAM problem could be the way they are driven. I remember my TRS-80 had resistors in the data lines between the DRAM and the TTL chips. Maybe Commodore decided they could do without them.
Instead of ditching that heavy RF shield, why not replace the thermal paste or add thermal pads. That's a lot of metal and _will_ help cool those chips than having nothing at all
I'm in the UK and I've had about 10 64Cs. All were short boards. All but one had the cost reduced keyboard. About half had screw together cases (but no Torx bits at all). The rest were clip together cases, and of those about half had clip-in keyboards as well - so the only screws are the ones holding the motherboard in place.
I've only seen those clip together cases on videos. AFAIK those were never sold here
@@adriansdigitalbasement They're so much better for maintenance. Especially the keyboards that just clip in to the top case. I don't know why they didn't do that from the start.
The audio capture sounds great.
I guess I was lucky with last week’s video then. Because I had a weird behaving keyboard and I assumed it was the CIA and just went online and bought a used for 25 euros from a guy nearby. Perhaps we have more guarded here in the Netherland 😂
You mention removing the RF shield for better airflow; is it worth putting small heatsinks on the individual chips?
What is the RF shield doing (shielding RF, duh!)? Is it okay to not have it?
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..
ahh yes. the repairathon. what a great way to start a weekend
Ya’ know, I know people complain about torx screws being used but I prefer them. I’ve never stripped a torx screw and I’ve stripped plenty of Philips, pentalobe, and triwing screws. The only thing better than torx is square.
More more more C64.....love it!
Could the recent perifratic build of the C64 with ALL new chips be a source for the replacement 6526s? I think they used FPGA/CPLDs for the 6526.
Can you use a 6522 in place of the 6526? You know, the CIA out of a Macintosh?
Here in New Zealand, our C64c were made in Hong Kong (silver label on the bottom - and the Warranty Seal, which I think you should have tried to peel off!) - and they have the Philips screws. But still the red power LED and the separate video RAM. Some have the annoying cardboard shield and some the metal shield.
I was aching to listen to the SID sound test - it kept getting cut off ;) One of my machines (with that test cartridge fitted) doesn’t produce all the scales - and they all sound raspy (no triangle waveform), there’s no white noise, plus there’s a loud pop when the sound starts and stops. Yet when I play games on that same machine, they sound identical to the other - waveforms are normal and white noise is working. Weird!
Could it be that the voltage regulators send a slightly highvoltagein these machines and the ramchips are very sensitive to high or low voltage?
I DID fry my CIA once on my C64c, by switching joystick port, while the machine was on. After that, a lot of keys on the keyboard, and joystick did not work anymore 😞
An interesting video, you are an expert on the C64; I wish I could do what you do.
What do you do with these repaired machines? Do you sell them?
MT ram fails a lot on breadbin unit... on the c64c those ram chip most likely got damaged by overvoltage from bad psu...
When 5v is too high , the ram is most likely to fail first
Thank you Adrian, excellent education on this.
Glad you liked it! And thanks for the super thanks. :-)
I guess you could put a wood chisel on that seam and pop the top of the burnt IC, or CuriousMarc heats them and snaps the plastic case off.
Rammy will eat well tonight! Om nom nom!
TASTY VIDEO! Thank you.
since the entire machine is getting hot, RAM is probably least forgiving when it comes to temperatures and it wasn't even touching the shield to remove heat, Probably bad design - driving RAM to high temps - I'd guess. Maybe they picked wrong types of RAM for these machines? It's not as much of a problem on Atari 65XE
I would have heated and moved the warranty sticker over or put it back.
He's got a hot air gun, so you're right... a missed opportunity. 😁
Adrian. if you look at 48:05, you will see the Capacitor was pushed out of the way by the RF-Shield. And this Shield actually has holes to let them go through. Who assembled this thing that way? Considering the seal was unbroken, it either was slapped on later or this was a "new" machine, which is probably a customer returnal for not functioning on purchase.
I assume it was manufactured badly at the factory.
@@adriansdigitalbasement That would be a rare case, right?
@@Sypaka Since they had only just started manufacturing them in China around the time this unit was made, they might not have had sufficient quality controls in place yet.
@@TheUtuber999 Ouch. I wonder how many of the machines went straight into garbage at that time.
I recognized the warranty seal from my Amiga 1200, long time ago... Another problem with the Amigas: always the CIAs broke down, they were very sensitive for static electricity and plugging in devices while the machine was running, had a lot of strange problems with mouse, joystick and disk drives...
I suspect YOU see more bad ram in those machines is because Commodore was getting better at making their in house ICs so the overall failure rate declined on the machines but the proportion that are caused by RAM is higher (Since the RAM fails at a similar rate as before). Then, the Adrian effect makes you see a lot of them (Adrian effect - The probability that Adrian Black get a Computer is inversely proportional to its condition)
I have a c64c long board that has never been opened before me, but there is no keyboard bracket on the right side. The keyboard just sorta floats there. 🤔
Ah, I finally got recommended a recent video by you. Perfect opportunity to ask.
How does the ARMSID fare:
- With the new 2.15 firmware
- On a C64 / C128 with the SuperCPU (if you have one)
- On a Turbo Chameleon
- On an Innovation SSI card (or clone) for IBM-compatible PCs
- In a DualSID setup?
I should also probably ask:
Have you ever considered putting battery-backed SRAM on a C64 (for a “low-power sleep mode”) and turning it into a C64 laptop?
@@AmaroqStarwind I've only ever seen home brewed c64 laptops with people using the c64 DTV as the internals. Makes sense, the dtv's motherboard is tiny.
@@maxxdahl6062 Er... What's the C64 DTV again?
@@AmaroqStarwind The joystick plug and play c64 unit that you could mod to give it the IEC floppy disk port, keyboard port, joystick port and power supply ports.
6:40 ah yes, no longer effective any longer, no longer good at being effective at being good any longer, 😂
Could c64 design itself be killing ram? Abusing them, bad power etc?
D ram and poor regulation of psi can cause problems, check the supply stability or you will be replacing them again.
ya, the fat agnus chips were being dislodged by a speed bump outside of the factory on the way out.
Have you spoken to Mike Chi about your problems with the RetroTink5X?
Hm, my (German) C64C (not CR, afaik) doesn't have a heat/RF shield - never had. The standoffs/adaptors for the keyboard are simply single pieces... Maybe those could be obtained from other parts machines?
All the 64's I've seen in the UK had a warranty sticker and Phillips screws holding the case closed - any variant of the 64 😊
What is the problem if we have Interrupt BAD with Diagnostic Cartridge
Hi, Great video like all the other videos you do. Keep up the great job.
Glad you like them!
Fingering chips?
Is that sanitary for an 8-bit party? Shouldn't you wash your hands first? 🤣
Smell his fingers.
If Virtual Bench is crashing a lot, try to run it in administrator mode. If it is already, you can see if the software has a newer version available, or it is possible a recent Windows update broke it. Temp files for the program could be causing it to crash so you could look into a fresh install.
18:37 What happens if one is running a flight simulator, and needs to use the joystick and the keyboard at the same time?
three are fixed, two are sorted out
anyway, very impressive. congrats!
looking for a channel sorting out problems out of 386/486 period hardware. like necroware. anyone got any suggestions?
What is inside of those chips? Have you cut one in half?
I really do wonder if Commodore was getting B grade or C grade RAM off suppliers for the C64 due to how many they were selling, to increase production or save a buck at manufacturing time. one of those three. it's possible that it's not indicative of the brands themselves having an issue but what batch they came from and how commodore's factory got them.
Is it a good idea to try the bad ship again after you install the socket just in case maybe you had a cold solder joint or something like that that was fixed when you resoldered it? I tend todo that just make sure especially with such a rare component? A few time I almost discarded a good part, so I always check them.