The UGLIEST Repair of a Commodore 64 (Part 1)
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- Опубліковано 26 чер 2024
- This episode is sponsored by PCBWay www.pcbway.com
Support Noel's Retro Lab on Patreon: / noelsretrolab
Today I tackle what was supposed to be a simple black-screen repair of a Commodore 64, and it turned into the ugliest repair I have ever done. If you're looking for a clean, efficient repair where all the loose ends are nicely tied together, you won't find that here. Go check out some of my other videos instead 😃
I still decided to turn it into a video because I think we can all learn things from this, even if it's not the prettiest one. I hope you get something out of it like I did.
Chapters:
00:00 Intro
01:35 Initial power up
02:10 Voltages, clock and video signals
05:19 Black screen
09:56 Bus signals
12:45 Voltage drop!
17:04 Bridge rectifier
21:35 Wiggle room
24:47 Back to work
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#c64 #repair #commodore - Наука та технологія
Instant thumbs up after that intro! 😁
👍
1:25 removing "annoying RF shield"? Adrian Black approves! :)
TBF, that paper shield is useless and blocks cooling.
@@Okurka. I don't think a company pays for design and built-in any component delivery for no reason. It has a reason to be there. Maybe RF interference?
@@ElectronGordo RF interference in 2021? No.
@@Okurka. No? :) ok, no.
Yeah I have seen Adrian just throw them away. What a laugh. Right guys, throw those shields away! :D
"That might make it even easier" are usually famous last words.
Great job, looking forward to part 2! I feel better about that voltage drop issue I had on that A3640 now lol =D Sometimes the simple stuff can trip us up more than the complex faults! The DIN socket and power switch are often a cause of voltage drop on these too (the contacts I mean).
Thanks! Seriously, sometimes simple things throw us off for a loop. Especially here because the voltage drop was only partial, I kept expecting some component to fail, not the dry joints!! I even triple-checked that the switch was fine (but failed to show it in video). Oh well. Lesson learned there. Now get read for part 2, which is when things start getting REALLY ugly 😱
Excuse me, where is the "ugly part"? Because all i can see is a technician on its best trying different methods to solve a problem!
Felicidades, Noel ; - )
Haha, thanks. The really ugly part is going to be Part 2 (not for lack of my trying). This was just a rocky start.
You need more views. Commenting for the youtube algorithm to be happy and suggest you to more ppl! Your videos are GREAT! I really like the live views into schematics while you're taking measurements with probes. Very innovative!
Thank you so much! Glad you like them!
on my behalf thank you very much
That introduction was hilarious, Noel! Great video! You definitely have a talent, not only in working with electronics but also in presentation.
Glad you enjoyed it! 😃
..to be continued! Nice to see some not straight forward easy fixes but some every-day-issues :)
A total cliffhanger!
I do love the way you explain and troubleshoot fails as well as the graphics in video (well made indeed)! You've got one more thumb up and one more follower! Congrats! 👍😁
Awesome, thank you!
Great work! Appreciate the methodical problem-solving approach and looking forward to the next one!
Awesome, thank you!
Another great video Noel - Always enjoy your work!
Thanks. Glad you enjoyed it!
The intro to this video made it totally worth watching. "You've been warned." LOL
There can never be to many c64 repair videos😁👍🏻 maybe some deoxide in the switch and power connector? Looking forward to part 2. Thumbs up!
I have a huge backlog of C64s to repair, so I'll be working my way through them interleaved with videos on other topics.
Excellent video, first time I have seen this channel, you sir are amazing 🎉
Nice to see again Commodore stuff ;)
Very funny intro, great video as usual. Gracias Noel :)
Thanks! 😃
Fascinating repair video. Probably an even better rule I suspect if there's wiggle with the power connector, is just automatically refresh the solder joints. Even on the chance that they look good under magnification, the situation will change for the worse soon enough from the added stress on the solder joints from the component being able to wiggle when inserting or removing the power cable.
Good ‘ol layer 1 problems. (Physical Layer) 😬 Well worth it for all we learned about diagnosis of power problems ... thanks!
After the intro, I had to get up the courage to see the rest of the video. Some scenes were too much for me and had to cover my eyes, but I can't wait for the second part. Amazing video again. Congrats Noel :-)
🤣🤣 Just wait until you get to Part 2...
loved the intro!
Great video. Thank you for sharing!
Yeah, on my C64 the PLA actually took out the ROM's as well. So some times when a PLA fails it is possible it could take other components with it.
I was watching Adrian's channel and he was building a GAL based PLA replacement and I decided to build one. Worked great.
Here in the USA I acquired a 2364 adapter(s) from go4retro so I could use more common 27C64 EPROM's to replace the dead ROM's in my C64.
Otherwise so far I have been lucky and haven't had to replace any other parts on it yet.
That's it, Noel!!!! Yes!!! Keep it coming. You're getting so famous. :D
Good job Noel!
Thank you!
Glad to see more use of a scope in Commodore repairs. Plan on repairing my original owned 64 after building a power supply. Found a donor machine at a flea market but just found that it has a PAL video system. Funny finding one in the U.S.
I had this revision of the board in 1984, my first computer. Mine was a French import, with a Philips pal to secam converter fitted under the keyboard by Procep, the company importing Commodore in France at the time. My computer had also this issue with the power plug. The shop to whom I brought the computer for repair made the diagnostic of a too power hungry setup, and removed the secam converter, eventually bringing the computer back to its pal version. Unfortunately, my TV set wasn't pal compatible, so until I had the money to buy a new pal + secam TV set, my Commodore 64 was B&W...
This video's great to remind us that we shouldn't panic and that the best explanation is always the simplest!
Can't wait for part two :)
Glad you liked it! Part 2 might be a disappointment though 😬
@@NoelsRetroLab Now you got me even more curious! 😁
Thank you, Noel. For the great thriller;)
I felt very sorry for you in the end. I knew it from the start because I had exactly such a bug over a decade ago with my C64 (worse, the switch had not bad contact, but was dead -> I didn't follow the iron rule: never turn off your computer ... or was it "never touch a running system?", hehe). I also know from maintenance: It's mostly there where people are fiddling with it! Plugs ... sockets ... switches ... big red buzzers, hehehe. They break everything! Therefore: Always check the mechanical wear parts first. Or at least have it in mind. That saves many hours and hair loss :) Now I'm watching part 2
Thanks for the video. I hope you get success.
Thank you! Much appreciated!
Thanks for the video =)
Good Job 👍🏻
Good Show! Outstanding "video" & "audio" and "post production"... You're hired!
Deal! 😃 (Thank you!)
YES! It's one of the most professional, if not the best, video channels about retrohardware repair and modding. Maybe others could be more savants, but no doubt that Noel makes truly descriptive and pro videos
13.7K subscribers. Well done, Noel. :D
Thanks! 😃
Very good and informative video, thank you. Nice explanations of the parts! Anyway, i think power switch could be very common issue of the c64 :)
Thanks! Yes, switch problems are very common, and I actually checked it multiple times (even though that didn't make it into the video).
Hi Noel, superb video. It remembers me on these days were you type-in programs and suddenly the C64 lost power before it was saved. Then my father and I remove this ugly thing with a new plug with screw connection. No direct contact to motherboard only wires. This was cool. And nobody can unplug the computer by accident.
Nice! I've never seen one of those, but that's a good solution if it kept getting unplugged. Back then I always had the problem that the power might accidentally go out for the whole neigborhood for a few seconds (especially during storms).
But bad solder joints was something my teacher in college was always on the look out for. When we soldered a component and snipped the legs short, he’d see and have us reflow it. Never snip and not reflow. And also mechanical parts were never allowed to be just soldered, always needed to have screws or bolts in place.
He was an engineer for ESA making satellites. And they found that these two things caused 90% of their problems. On earth oxygen would get into the hair tears and would corrode . In orbit the extreme temperature difference would work that solder joint repeatedly (or same with components that get warm) and eventually fail the joint.
So he was really meticulous in checking our joints. And after that semester, I never looked the same at consumer electronics. So bad the majority of them are. Not made to endure, and these days it’s even worse.
Totally right. I wouldn't advocate doing everything at satellite standards, but some things can be much better. Having some screws in the power connector would have cost Commodore a few more pennies and would have been much better. But then again, they may have been fine for the first 10-20 years and it's only now that we're getting those problems. And yeah, modern devices are orders of magnitude worse! 😬
@@NoelsRetroLab But we get so much fun from these old machines :D So I would've liked them to engineer them to proper customer electronic standards :D Although generally they are holding up really nice. I just had an MSX come in. 1988 and the only thing the previous owner did was change the floppy drive belt.
And I learned a valuable lesson today. I had this 16LED bar display made for the C64 (to learn KiCad and test PCBWay). And since you get 5 board for 5 bucks I made one for the MSX too. And I noticed that when I toggled the STROBE that the lower 8 bits also got updated. Turns out that the STROBE bit actually is not completely in your control. But when you send data, it will briefly go down to inform the printer. And down in my case is, activate the other latch :D I never knew that about parallel ports! And the C64 user port isn't a parallel Centronics standard so PB2 is just fully in my control. But I figure I can make it "look" okay when I quickly enough write both bytes out. This was the idea anyways to polish my 31 year old Z80 coding skills.
I do like the MSX (I was triggered by your love for the Amstrad, also a Z80) I was a N00B until 3 days ago. We had one in school but never got serious about them. But it's quite interesting, like the Amstrad I guess. Also a bit quirky with the VPD. Which doesn't allow you to write immediately in the NVRAM, you have to go through an IO port. And basically have two calls one to set the address, and one to push the data. Unless you do consecutive writes then the VDP address is incremented. But then you run into timing issues because if you do it too fast :D
Interesting stuff. So much, more fun than X64 PCs ;)
Keep up the great work, I adore your chancel. And I am amazed how many great hackers there are of these old machines in Spain!
Excellent vid...future man😄😄😄
Haha, that was definitely a message sent through time from the past until... right now. So yes, I'm definitely future man. Sometimes time travel works! (especially in that direction 😃).
Great to see you back with the breadbins again. Recently i've been struck by two machines with blown up fuses, one was an c64c and the other one an breadbin.
Thanks! Oh I have a huge backlog of C64s and VIC20s to repair, I just haven't been able to make time for them. There will be more for sure.
Were the fuses the only thing wrong with those machines? That's lucky!
@@NoelsRetroLab It was strange with the 250469 board it seemed to work fine otherwise except there were no sounds. I tested to 8580 SID chip in an another machine and it worked just fine. Then i watched Jan Beta's video where he was fixing one of his c64c's and from there it occurred to me that hang on maybe that's it and after examining the fuse it was not good. Put an new one in and board has been working just fine since then. With the breadbin i found no power on both 7805 and 7812 voltage regulators then i examined the fuse and put in an known working one and that 250407 board came back to life and the voltages seem okay.
Excellent video! Funny thing I'm working on the same black screen and same board version. Come on part 2 :)
Honestly, it can be anything.... as you'll see in Part 2 😬
You made me shout at the screen. Check the power switch and the socket! 78xx regulators can go bad and engage in the shutdown all the time, but that doesn't cause their input voltage to drop, only the output drops. They can go short circuit inside which of course overloads the input supply and cause a drop but things will get hot very quickly in that case. They can develop a short between input and output pins, in which you'll see the input voltage on the output pin and things will go bang quickly... So, it was obvious they were not receiving power, which can be the socket, the power switch or anything in between those and the regulators.
Haha, if it makes you feel any better I had checked the switch multiple times (but somehow didn't record it).
@@NoelsRetroLab No it doesn't... :-(
Just kidding :-)
Shouting at a computer screen is the best part of being a nerd, so I guess it happens quite a lot on these retro computer repair channels like yours. But yet, IMHO, the tracing of a power fault should start from the point of input, not vice versa . Old electronics like these are very likely to have corroded socket pins and switch contacts, cracked solder joints where mechanical stress is frequent. They are the usual suspects if it is an intermittent fault like you had here. Can't wait for the second part, I have more shouting to do. :-)
Hi Noel. You seem to have at least another cold solder joint on the cartridge port. I think I spotted it as the last one visible in the bottom row on the last shot of the board flipped upside down.
Keep up the good work!
I think you're right. I should have another look. Maybe I can even add that to the start of Part 2 since I haven't exported the final edit yet. Cheers.
Hi Noel. Missed the past few videos due to "life", thanks for your entertaining content.
Pesky life getting in the way! 😃 Glad you're back and hope everything is well.
Great video.
Glad you enjoyed it!
Your intro had me riveted to my screen!
1:10 There is a little slot on the left side of the VIC-II shield where you can wedge a flat-headed screwdriver and pop the lid before you slide it to the left.
Ah! I knew there had to be an easier way to open that! 😃 Usually, if I have to do any kind of work around the VICII I end up desoldering that little metal cage and fitting some heatsinks directly on the chip anyway.
Thanks for the video .Commodore beautiful
Glad you liked it!
I see no problem with what you did you tracked the problem down, maybe round a couple of streets a town and a village but very enjoyable great video
This was just warming up with a rocky start. Part 2 is where the real ugliness starts 😬
This video remembered me two problems with my Sinclair Spectrum. In both cases the computer just "turned off" after some time working. The first case was due to a physically broken diode in the power suply: when it heated, the connection broke and stopped sending 9 volts. The other case was much more subtle: I removed and mounted again several times the internal heat sink, and accidentally broke one pin of the voltage regulator. Anyway, it held in place... until it heated, and it was so subtle that I needed several days to discover it.
Oh wow, yeah, those are the worst kind of failures. Intermittent ones that only happen sometimes or after some use. Even here it was driving me crazy because I would try something and it would start working because the power connector was making better contact, and then I would do something else and it would stop. It can be quite frustrating!
Love that t-shirt!! Where could I get one?
Great video Noel. I guess it's always a good idea to just reflow the pins on the components that take som abuse, like the power connector and the power switch. Even if it's not an issue at the time of repair it might still prevent issues in the future.
I'm excited to do some more work on my C64's now! 😅 I've been doing some upgrades in my lab so I haven't been able to produce videos for a while.
Sure, if you know it happens enough, it's a good idea. Normally I have problems with the switch, but not with the power connector so much. I guess I'll be looking at it a lot more closely from now on 😃
AC Current? Alternating Current Current? 😎 Good video.
Haha, didn't even realize I said that until now! Doh!
Great video, maybe check the PCB upside down next time? Broken traces and bad joints are more common than people realise and connectors to the outside are always prime suspects. I found that out with 80s audio gear like synths.
I didn't see any messy stuff, am I missing something? :) Really nice video.
This was just a rocky beginning. The really ugly part is coming in Part 2 😬
This happens a lot on audio equipment too, typically the RCA jacks :D I've fixed a few issues on Sony gear by resoldering the input/output jacks.
Right. I've seen it a lot in Amstrad CPCs too, but it's usually binary: You either get full voltage or it stops and you get nothing. Here it was really weird and intermediate. Maybe because it's AC and one contact was fine and the other one wasn't?
Ace detective work!
good job!
Thank you! Cheers!
Nice. However, when using a dead test cartridge, you also need the harness. The harness is a series of connectors which plugs into all the ports on the system and there’s a separate connector for the keyboard. Without the harness, it will give out inaccurate results. The harness is necessary as it provides loopbacks which will give you a more accurate result.
Sure, that's ideal but unfortunately I don't have the harness. I should get one sometime. The memory test is still valid, which is mostly what I'm using it for.
very nice!!!!!!
Thanks!!
Interesting to note that the leftmost IC (7406) in the second row from the bottom left corner of the PCB is a Romanian part made by IPRS. It is only marked with the β symbol. Looking at the date code reveals that it was made in 1984. That thing just caught my eye. Otherwise nice work in general! I really enjoy your videos.
First try! Hehehe. I love the content you are producing, keep it real!
Ok, Noel ... and WHERE WAS THE UGLY part? I didn't see anything ugly. Instead, professional as always! :-)
Other thing, that happens very often, that the power switch itself is bad (switch internal contacts)!
So looking forward to part 2!
Greetings, DOC64!
Thanks! The start was rocky and a bit ugly (forgetting the video connection, spending forever tracking down power issues), but the really ugly part comes in Part 2. Just wait 😬
Funny - only yesterday I had a similar problem with the power switch.
...as a founder member of 'RF Shields Matter' I wish to lodge a formal complaint..
Haha! 😃 But actually go ahead and convince me they're worth keeping (I'm being serious). Do the RF emissions from a computer like this go far or are they limited to the range of my house for example? Because if it's just me, I don't think it affects me any, and the electronics in there will be a lot happier with the extra ventilation. Now if it has long-distance effects, then I could see it being a problem and I'm happy to change my stance.
@@NoelsRetroLab Do any of your neighbours listen to shortwave, are they radio hams? You may be interfering with their hobby.
@@M0UAW_IO83 I have a few shortwave radios and 2 older computers without those shields and I have no problems. Perhaps with some AlieExpress shortwave recievers there might be some problems, but I guess they don't like striplights too.
My first thought: old and shorted electrolitic capacitors ;)
My man’s sponsored now! Yeah! That means things are going smooth... waiting for that “I left my day job” video anytime soon... XDDDD (jk, but happy to see a sponsor)
Thank you! Yes, it's going great. The sponsorship and Patreon has been helping a ton. Right now I'm committed to a project for work for about a year and a half, but once it is over, I could see giving this a shot full time for a while. I could do SO much more than I'm able to right now!
@@NoelsRetroLab I’m so happy for you! I hope you can make it, so it gives you time to make great content. Kudos!
Edit: random though: I always envisioned an ”I.T. Crowd” kind of intro for your channel... I wonder what you can do with more time and money...
I wasn't even thinking of a professional intro, but that's true. I want to keep it super short, but it could be fun having a high-quality one!
Thank you.
Future Noel is scaring me :( Maybe I shouldn't be here D:
lot of evidence of rework in that area near the power connector, so not so surprising to see problems. Also looks like a couple of pretty bad reworked dry joints on the cartridge connector
Good point. I saw the differences but I didn't instantly think re-work and I thought maybe it was done at the factory. I should have another look just to check.
Wiggly power connector - weird. Have you ever seen this on any other computer brands?
Yes, quite a bit actually. Happens on Amstrad CPCs quite a bit (even though it's just a barrel jack), but it's usually an on/off thing. You touch it you get power, you touch it again, it all goes away. Maybe here because we have multiple pins and AC current it causes that partial current draw that threw me off.
The GAL-PLA that created by Daniël Mantione is cheap and good for testing bad C64 board, the PLATinum is expensive, once it go bad it cost a lot.
This particular one is pretty inexpensive, around 5€ or so already assembled. I haven't tested the ones you mentioned though, so I can't compare them.
I see a custom MOS 7712 two left of the SID. These just love to fail. It's a 74LS08 it looks like.
EDIT: And I did see rectifiers doing exactly that - just randomly failing under load
Oh good eye!! 😜
Noel, noQL or VDrive that I see. (Whoops not Christmas Carol time) Hmmm Maybe next time Hmmm Lol
I'm already shooting that one, so expect it in two weeks 👍
@@NoelsRetroLab Yay :-)
I actually got my VDrive for the Spectrum today. Hmmmm :-/
Is your scope grounded?
I was suspecting the power switch.
Yes, that's one of the first things I checked. I even checked multiple times but somehow never recorded it. Go figure.
This is probably a dumb question but where is the camera? Is it in front of you and you reach around it?
Haha, yes, that's correct. It's on a tripod in front of me. So pretty much the same view as I have of the workbench. Also explains why I'm often kind of clumsy doing something on camera, because it's not the most natural position in the world 😃
@@NoelsRetroLab Thanks, I just couldn't picture where it could be without occupying the same volume as you do!
Dammit...could have saved you the trouble, because I has the exact same fault on mine 35 years ago (luckily I could trace it immediately to the same solder points because I had noticed the play in the power socket some time earlier, as the machine was being moved/unplugged/replugged a lot). Using solder points as a support of parts that get occasionally put under mechanical load is a somehwat dumb design decision. I guess they figured you'd just plug it in at one place and leave it there forever.
That's crazy that that same problem was already happening such a long time ago. I guess it's mostly due to stress rather than just age.
Jan Beta Retro lab
😀
Too many good retro channels
Pesky ol' solder joints! I hate then that happens!
Yeah, especially because this one wasn't on or off. It was "kind of passing voltage but not enough", which really threw me off for a loop.
@@NoelsRetroLab The rule of thumb.... always check the power supply from the very start.... ie.... the wall plug.... then after the transformer...then the connector..and so on and so forth. Lots of time can be saved.
@@GORF_EMPIRE True, but that's exactly where I started 😃 It's just that it decided to fail after I was already happy with the voltages!
@@NoelsRetroLab Ah ok I did not recall that in the video so I mentioned it.
Joke's on you, I only had to look away twice.
🤣🤣
Dry as a dead dodo’s dingo! (c) EEVBlog.
*dingo's donger
Shitty switch, when passive components are breaking your system, you’d better run and hide :)
dat shirt
Best shirt! 😃
OK that was maybe a kid stomping on the power cable? Show us the real ugliness🙂
Coming up... in part 2 😬
Anything retro computer cannot be that ugly lol.