These Sixty Clone boards are works of art. That you can buy such a nice board for $40 US is a testament to how far PCB manufacturing has come. 10 years ago I paid $1500 for a 4 layer board as big.
Should have tested that capacitor, it may be all over the place after being reversed, and I wouldn't trust it further than a throw into the dead parts bin
@@NoelsRetroLab Tantalums especially. Once you heat them up or break down the oxide layer they are time bombs just waiting to short dead solid. Tantalums had much lower ESR than aluminum electrolytics in those days, and nothing else in the same size range had the same capacitance if you wanted 1uF or more. These days just replace it with a low-ESR electrolytic.
Yellow/orange Tantalums are actually quite common - at least on PC hardware (which I deal with a lot). Usually they blow up spectacularly when you mess up polarization but I guess the voltage in this case was just too low to provide proper fireworks. Actually Adrian Black had a spectacular one blow up in his digital basement in one of his recent videos.
Haha, yes, I just saw it!! Probably because I work more on older computers, I tend to look out for the little blue caps, but you're right, they can be any color.
I spent most of the day trying to get a PiStorm (I built from parts) to work. No luck, until a few minutes ago when I finally noticed one bad SMD solder joint. It's that breakthrough moment, that makes electronics fun.
7:36 they used a tantalum because it has higher capacitance per volume than ceramic. If you look carefully at the schematic you can see that near the left capacitor is a .1 (uF i suspect) when near the right capacitor is a 4.7 (uF again i think). Nowadays they are all yellow (including SMT packages). Ceramic now include higher capacitance values but I would not be surprised if in the 1980s there were not. Also in this case the tantalum is used as an energy reservoir rather than decoupling (that’s a job for ceramics) so that if the voltage were to dip for some microseconds it would hold the voltage up while discharging. My guess is that a voltage dip would cause some kind of glitch, maybe some register losses of some kind
The Tantalum capacitor used as a low impedance Coulomb (Charge) bucket. They are often used on power supply rails that are a fair distance from the voltage regulator.
I was just about to write a comment to that effect. They have a nice low ESR and make good decoupling capacitors. They also really do not like to be reverse biased!
They're damned dangerous things particularly when becoming old or subjected to overvoltage where they can spontaneously ignite and launch themselves as burning fireballs!
Yes, the low ESR enables them to dump or build charge faster. Combined with higher capacity and better temperature and frequency stability than cheramic, they are a typical go-to for decoupling digital circuits.
Ceramic capacitors above 1uF start to be more expensive. Tantulums are cheaper at high capacities 1-100uF, after that electrolytics start making more sense
If I recall correctly, they're smaller than a ceramic for those same capacities too, because they're technically an electrolytic themselves (just not an aluminum, and either partly or wholly lacking aluminum electrolytic's "self healing" capability).
Back in the 90's when I was doing board level repair for GE I ran into this often as the boards were populated by hand and I got all the failed ones from the line. Good Job, looking forward to the conclusion.
Noel, excellent troubleshooting of that board. I’m a relatively new electronics hobbyist and am always looking for tutorials that teach the logic used to troubleshoot electronics. This video presented your troubleshooting approach in a very clear and logical fashion. As such, it was one of the best troubleshooting tutorials out there for someone new to electronics. Keep up the excellent work my friend.
Thank you! I'm really glad they're helpful. I also learned a lot initially about repairing computers from some early repair videos, so I totally get it.
These videos from people like you, Adrian's Digital Basement, and Jan Beta (and others) REALLY contribute to the overall knowledge base that will need to exist as these machines fail. Thank you for that! It was much harder before RUclips videos from contributors.
Don't know whether you are aware, but there is a small rework required on that version of the board to fix where a misaligned via causes one of the cartridge port pins to be shorted to ground. Not sure whether that would cause the issue you are seeing, but it does stop a number of cartridges (including epyx fastload) working correctly until its fixed.
Yes, good point. Rob told me about it and I checked, but it was already fixed on that board. I didn't include it in the video to avoid confusion, but you're right that it could have been causing all sorts of weird problems.
A tantalum capacitor is used here because its characteristics are very similar to an electrolytic: high capacitance in a small amount of space, but unlike electrolytics you don't have to worry about them drying out over time. However, you still have a high ESL similar to electrolytics, so for decoupling power rails you'll usually run them in parallel with a smaller value ceramic capacitor to make up for that. That's exactly what's shown on the schematic at 7:25, you've got a 100n ceramic in parallel with a 4.7µ tantalum. Other chips only have the 100n ceramic likely because the amount of noise they would dump out the v+ pin is small enough that it doesn't need the extra farads.
I had exactly the same problem with an old Soviet calculator. After replacing all electrolytic capacitor it started up and then died in ten seconds. One capacitor was installed backwards...
Great work as always Noel! I'm not surprised the original owner was having trouble diagnosing this, I can't wait to find out the ultimate cause of all of these strange problems!
Thank you! I think you're going to like the root cause of the CIA problems. That's why I decided to save a whole episode for it, so I can take the time it deserves.
I love these videos. I appreciate a person who can start what might be a 5 minute adventure or a multi part series depending on how deep the rabbit hole runs. You make time to educate about what must be basic concepts for you with imagery in the midst of it all. Pure skill definitely is a thing but I think I appreciate the way you communicate making really daunting things so digestible. Thank you.
Wow! I just built a Color Maximite 2 and it had some tantalum capacitors. I had no idea they were polarised.. amazingly enough I had 3 soldered the right way around. Very lucky!
Great video, really enjoyed it and looking forward to part 2! I have my own 8088 Clone PCB being made at the moment, so I'm going to be populating that with old chips soon and interested if I have to go thought a similar journey of how to fix something that never worked in the first place, fingers crossed....
When building a kit, you don’t just solder everything in place, cross your fingers and expect it to work, instead you construct it in logical stages with component value checking as you go. For instance, initially assemble the power supply regulation circuit and check to see if it works, then progress to the next stage which might be installing any clock circuits.
True, that's probably a better way, but you need to be intimately familiar with the circuit itself to pick the right order and make sure you got all the components required up to that stage. I suppose a kit could provide those instructions, but most of the ones I've seen just have you solder everything, and at best, they'll provide some checks afterwards. I do like your idea though.
@@NoelsRetroLab Many thanks for the reply. Most kit instructions follow that lottery approach. I designed and built commercial prototypes from 1970's onwards for many decades where it was necessary to use an incremental approach. In the 70's through mid 80's prototype PCBs did not have solder resist so careful soldering was required to avoid unwanted short circuits. I do really like some of the modern mod kits that use bespoke flexible PCBs to replace bodgy wire connection to neaten their installation.
Hello Noel, nice video and good desdcription as to what is going on. Tantalum capacitors are used on power supply busses because they lossy and have significant ESR ( equivalent series resistance). This damps the bus and prevents oscillation. The regulator IC is basically a power op amp and is subject to stability problems if the output is shunted by a low ESR capacitor like a ceramic. The schematic you presented shows a ceramic and a tantalum in parallel which is good modern practice. IC manufacturers have papers explaining this and some of the data sheets also have explanations. I have also read an interesting paper showing the effects of various capacitors on the performance of linear regulators.
Interesting! Those details are definitely beyond my depth of analog electronics, so that's really helpful. I ended up replacing it with an electrolytic one of the same value. Do you see any potential problems with that?
Excellent video! I have one of the replica boards and everything to populate it. It's going to be a winter project and it will be interesting to see how many mistakes I make and need to troubleshoot!
How long did it take you to source the parts for it? (TBH I'd love to try doing either a C128 [what I owned growing up] or an Amiga 500 [always wanted one] )
I'm didn't risk to put same tantalum back.. Probably, it now has a minor internal damage and now it's just like ticking time bomb.. Great, that video chip was ok! This will be interesting to see why ports is reported bad and what's causing it! 👍😉
Nah, I trust my oscilloscope to see that we had a black screen 😃 (actually, I think I did plug it in and it just confirmed there was signal but black screen).
The combination of the two capacitors should do the following: the 100nF eliminates the HF ripple, the tantalum capacitor intercept the pulse peaks. The ESR value is lower than that of normal electrolytes. In most cases, it can be replaced with a LOWESR electrolyte. I would not leave the reverse polarity tantalum in the circuit because it may be partially damaged.
As someone that has worked with repairing electronics for 30 years myself, with a completely new board you cant even rule out that the traces are correct,something that you didnt mention and came to mind when you had the shoring problem of the 5 volt. I have personally had both shorts and breaks in the traces on new boards that the traces were supposed to be electrically tested on, not the most comon problem, but still. Great to see that there are people building these things, i still have an aoriginal breadbox Commodore 64 that i boight new back in the day.
Good point. I didn't go there because I knew that this board design was already tested and working with other people. But you're right that there was always the possibility of this one being defective somehow.
@@NoelsRetroLab Sure, but what i was talking about wasnt the design but rather the possibility of a manufacturing fault of that perticular PCB that you got in your hands, like i mentioned it has happened to me in some cases that one board out of many had faulty traces.
That tantalum cap that was connected backwards will have been weakened by that. I would replace it anyway even though it "seems" to be OK, and I would replace it either with an electrolytic or a ceramic. Tantalum caps are more trouble than they're worth.
Agreed. I'll swap it out as soon as I pull the board out again. I honestly didn't realize they would be permanently damaged, but everybody seems to be in agreement about that. Thanks!
@@NoelsRetroLab : The issue with tantalums is that like aluminum caps, they're electrolytics, so internal misconfigurations of the chemistry are caused by reversing their polarity (which is why electrolytics require a DC bias to properly handle AC uses). However, while aluminum electrolytics will _slowly_ repair themselves if subjected to a low current of the correct polarity, tantalums don't, and supposedly go through some sort of collapse cascade.
If you're going to swap it with a ceramic, just leave it out. Tants have different frequency response than ceramics do, so replacing it with another ceramic won't help. There's already a ceramic on that rail.
I think you're right. I didn't know about that but other people mentioned the same thing. Maybe the 7805 helped it a bit by shutting down, but you're right that it would be safer to replace it. Probably an electrolytic one would be fine too.
They way they made them in the 80's was to buy defective memory chips for next to nothing, that could only address half their capacity, use the half that worked in each chip and mount double the number of chips.. Sinclair did this with one of their ZX Spectrum revisions. I think it was with 4164 chips, not sure Or was your comment a sarcastic nod to this?
@@paulmichaelfreedman8334 I understand perfectly what you say and no, I wasn' t sarcastic at all. I just quoted the obvious: Somebody bought something in 2021 and it just didn' t work...
@@paulmichaelfreedman8334 You are correct, Sir; the first few revisions* of the ZX Spectrum 48K used those "half" 4164 RAM chips. The boards were designed so that by soldering in some jumpers, it could accommodate chips with either the lower half or the upper half working. Another set of jumpers allowed the use of RAMs from different manufacturers. *Except the very first version; that one used a small daughter board that sat above the main PCB.
The value of that tant is 4.7uF (shown both on the schematic and visible written on the cap body) You aren't going to find a ceramic with a value that large (ignoring modern surface mount MLCC caps) It'll be providing a bit of local bulk capacitance for the VIC IC alongside the 100nF ceramic decoupling cap that's in parallel with it.
True. I don't know why I had it in my mind that it was 1uF, which would have been in the upper end for a ceramic one. So I guess the real question is why not use an electrolytic capacitor then. Were they significantly more expensive?
No idea about price differences back at that time. In that application I wouldn't have thought performance differences would be a factor. Tants will tend to be physically smaller, but there doesn't appear to be a space problem - could always have used an axial elec. if there were height concerns. Really easy to overlook it sat alongside all those resin dipped ceramics though (and the schematic not actually putting any units next to the value doesn't really draw attention to it either - it *could* have been 4.7nF - although that wouldn't make much sense in parallel with a 100nF decoupling cap).
I've built a sixty clone replica and it worked fine since the beginning (I was amazed to discover I didn't do any mistake, and even if I used jumpers instead of the ferrite stuffs, it worked -and works yet- flawless). That's the C64 I'm using habitually.
That's great! I'm still unclear why the original board is full of ferrite beads. I get what they do electronically (kinda) but I don't understand why they felt the need to use them everywhere. There are other computers of the time without a single one.
I noticed that, too. I have red, green, yellow, blue at hand. This is usually a color code for the maximum voltage of the tantalum capacitor and it is possibly manufacturer dependent. But there is also a norm specified. Search for "Capacitor Voltage Colour Code Table". In that yellow is 20V and blue is 35V for Type J (Dipped Tantalum Capacitors).
Also: The reverse driven of the capacitor possibly has the electrolyte and foils damaged and it has a very shortened lifetime. It is better to exchange that capacitor with a new one.
These detective / resurrection episodes are fantastic! Question / concern: When you changed the voltage on the RF module to +5 by unsoldering the pin and running a wire ... is there any risk of accidental contact of the pin still present in the unsoldered hole (perhaps by vibration if the machine is moved around)? Would it be appropriate to snip off the pin on the “bottom board” of the RF module?
Thank you! No, there's no concern about accidental contact. I actually removed the metal pin completely, so you're left with the plastic from the pin header separating the two solder points.
There's something incredibly aesthetic about 80s electronics. That specific tone of blue (or sometimes green). Maybe it is the text font on pcbs. The size of the components. Ahhh, I don't know. Excellent video. I think that Moore's law is about to reach its limit and we will be seeing more people getting creative solving problems with some vintage ideas. I don't know about using the RF out for monitoring though haha
I agree. I think a lot of it is also due to the fact that you can wrap your head around one of those computers intimately and figure things out yourself. Once you move into the 90s, things start getting a LOT more complicated.
@@NoelsRetroLab If I were a professor I would personally teach computer-applied electronics basics on old high level computers (C64, AMIGA, ETC.) rather than new low level computers (Raspberry, SOCs, etc). And yeah, I'm a 90s kid (not a kid anymore actually haha) and I remember the HUGE spike between pentium generations and how Windows XP was "impossible" to run properly. Such thing hasn't happened nowadays. And with the semiconductor shortage, the hardware spikes will get even slower. It sounds "bad", but is it?
@@tspawn35 Agreed. And also with this "circular economy" tendency today and the insane amount of electronic waste we do, there is a lot of good stuff that could happen. In my country, repair shops now only repair blenders, refrigerators and stoves. I have some broken LCD displays, fully functional CRTs, motherboards and Pentium 4 era hardware (PCI tuner cards, IDE drives, DSL Modems, etc) that don't have a "use" anymore but I just don't feel like throwing them away. As you say, doing board level repair makes sense as it is cheaper but I'm no sure if it is, you know, "marketable" for companies to let you repair your stuff :(
@@SUP3RP3DR0L1V3Was also thinking about the whole idea of how you might teach programming, and the vintage systems that have the OS baked onto the hardware (like the Commodore machines) also have another huge advantage--it's VERY hard to screw up the machine itself---e.g. a hard power cycle will put you back to a known good state. Have you heard of a project called the Commander X16? This is a "modern 8 bit computer" based off the vic-20 architecture. This also got me thinking (and yes most of this is a pollyanna view :D )....once the CX16 it is released in kit form, would be some sort of "summer program" that would teach both the lower level programming and practical soldering/electronics. The idea is the students would either start on the emulator, or physical CX16s to learn the coding, but along side of this, they would also learn practical electronics/soldering/debugging as they assemble their own CX16 from kit. At the end of the program, assuming things went well, they'd end up with a fully functional "modern vintage computer" that they get to keep
@@artstrutzenberg7197 I'm an IT Engineer personally and only took a small subject on electronics at school (my university had a totally software-oriented curriculum, maybe some networking over here and there). I learnt to understand high level programming languages just by practicing and not reading theory or the principles behind it (it was cool at the beginning). But just when I thought I was a prodigy, I got hit in the face by some OS scripting problem on Linux (due to PTSD, I rather not remember what it was haha). Programming logic at OS level (C modules on linux) is a WHOLE WORLD different to what I do at work as a Web Developer. From there, I started to try to understand the "low level" under the iceberg but that led me to needing to understand (and I mean understanding, not what I used to do back at school :P) math (discrete math, algebra, calculus, numerical analysis) and electromagnetism and optics (physics). At the end I ended up here, talking about electronics which is the basic form of modern computing. So, if you look at it, I did everything that was needed but in the opposite way (Frameworks -> high level programming languages -> operating systems -> electronics -> basic sciences). The way I did is a very good way of keeping interest on the students, but a terrible way to actually understanding stuff. So, you should go step by step of technology (Basic Sciences -> Electronics -> Computers -> Low level Programming languages -> Operating Systems -> High level programming languages -> Modern Technologies). Commander X16 as a project or even as a whole subject to study on the first courses (if not the first one). Keeping your first computer is a literal milestone hahaha
Before you waste too much time on that cassette port, make sure it's even supposed to work. I had thought on the new C64 boards the cassette port wasn't 100% compatible.
A tantalum capacitor as more capacity than a ceramic capacitor. They are always used in tandem because the ceramic capacitor as a fast transient response the tantalum does not have.
A great video with an interesting topic. I'm owning a c128 with keyboard and system pcb problems. I was already sneaking on the web site of the builders of those pcbs. They have a new 128 pcb too. I will use your excellent video as guide. Top diagnostics time!!!
Ugh. That's bad luck. And the worst thing is that resistance checks wouldn't work because all decoupling capacitors would show up as shorted. Did you have to desolder them all, or did you track it down with sensitive voltage measurements?
Very interesting diagnostics on the board, super nice board, ive considered getting the C128 version and retro fixing an old 128, could be fun. Great video!
Lol "they are usually blue" - nah in all my years I've seen more yellow tantalums than any other colour. A 4.7uF tantalum is / was cheaper than a ceramic back then for similar performance. I would have thrown that capacitor away, tants have tantrums (boom tish) when hit with reverse polarity.
Yes, I hear on PCs are mostly yellow. Not sure why, but in most of the computers I work with they tend to be blue and my eyes are trained to look for them (especially because they short with time).
Hey Noel, when the CIA has no order they will do strange things. Now I have learned new things about tantalum capacitors that I don't expected. Thank you very much.
4.7uF - 10 uF tantalum capacitors were very commonly used for power filtering in 80's-90's designs, and in fact they are still being used. Higher capacitance MLCCs were not available back in the day, and even now they have some drawbacks, for example their capacitance goes down significantly when the voltage is applied. BTW, I am curious what 8088 board do you have. One of my designs?
That makes sense. Is there a reason to use tantalum over electrolytic in that case, or is it a perfectly fine substitution in that case? And yes, I believe the boards I have are designed by you now that I think about it! 😃 I've had them for a while, but I'm hoping to do the build sometime soon. Thanks for making that project. It looked amazing!
@@NoelsRetroLab tantalum have better filtering characteristics at high KHz to low MHz frequencies - ie exaclty the frequency area that the buses would be operating at. Ie better at filtering any noise induced on the supply by normal chip operation.
I cut my 8-bit teeth on the Commodore 64 (with a special mention to the Atari 400 which was the first micro I owned). Those 8 bit machines were powerful enough to be interesting, and also simple enough so that a properly obsessed school child, armed with the provided documentation, could suddenly find themselves a budding computer scientist, with WarGames on the big screen to let us know the magnitude of what was coming. If you're a very young person seeing this video, know that the Commodore 64, first among equals of the period, was an absolute game changing personal computer, and many of your favorite games were probably contributed to by programmers who had learned the core, really important, lessons of computer programming on computers of just this type. Also, it wasn't even a "weak" computer. Color hi resolution high speed graphics (faster than the human eye, anyway), great sound synthesis, a peppy clock speed. Once you owned a machine like a Commodore 64, even as a child, and had read its operating manual, it was manifestly obvious that if you could master it, you knew what a real, powerful computer truly was, and that everything that would come after this would just be more of the same, better to be sure, but only quantitatively, not qualitatively, in accordance with Alan Turing's 1932 epiphany that, deep down, there's only one kind of thing anyone that can make that should bear the term "computer", &c.
@@NoelsRetroLab I read here and there that tantalum caps should stay stable longer than ceramic caps, so I guess it's down to quality. Commodore (among many) wasn't above buying inferior components to cut cost.
@@paulmichaelfreedman8334 : Perhaps they stay more stable in regards to e.g. temperature, but past a decade or two I'd expect the tantalum to be worse, because they're a type of electrolytic cap that lacks the self-heal capability of aluminum electrolytics.
Although it was not the problem, I thought that maybe it could help someone else, who knows. What I was thinking right away was “oh maybe the backplate of the regulator is not to gnd but it is a vout pad” (although i think it would have just blown the fuse). But it could be an error that some non-experienced person could do. So maybe some ebay regulators or the wrong package can really cause problems if you are not aware of the fact that the back plate on those can also be Vin or Vout other than GND. I don’t know, I thought I should share it. Let me know if you think it might be helpful or a totally useless comment
Its beter to replace the tantalum cap which was reverse polarised. Its damaged for shure, its just lost the most of its service life. Since they love to go short and burn... They are used since they riple smoothing is ten times beter then standard electrolite ones.
Have you created the video that shows what the problem was with those bad chip error messages? I was thinking about getting one of these boards, but after your video I am not so sure. Would really like to see how it all turns out. Thanks.
Definately replace that Tant! I was a little jaw-dropped when you just turned it around, after it had been reverse biased and had been sinking so much power! ie. It should no longer be trusted. Just say'in. :-)
Weird, I thought these Tantalums, once they start to short (for whatever reason, not just by being in backwards), they're toast. (although I had that happen to high voltage electrolytics - and after putting two of them in backwards I started triple-checking and guess what - I managed to put another one in backwards anyways)
You may be right about that. I didn't know that but other people pointed that out. The only thing I can think of is that the 7805 shut down faster than the cap was damaged. Alternatively maybe the cap was damaged but since it's just a decoupling cap, we can't really tell anything is wrong. Probably safer to replace it though.
Noel, probably I am wrong, but... at least it seems when you finally checked out the test with warning on cassette that the cassette cable is actually not very well inserted. That could be an explanation about why when you replaced the 2 "wrong" ICs still the same mistake, same point but this time only 1 is showed as wrong IC. Does it make sense?
The CIAs are both reported as faulty, independently of which ones I put there (it just takes another pass for the second one to be reported). The cassette part... I did show up as faulty and that just went away. I thought it was because I cleaned up the edge connector, but maybe you're right and it just wasn't pushed in all the way.
@@NoelsRetroLab Yeah, I saw a recent video with an FPGA SID playing Lightforce tune and it sounded OK at the bit near the end where most emulations fail. Not sure on the state of VIC-II direct replacements. CIAs are less important for now and most of the other chips are no problem as far as I know. Of course you have to recreate the exact smell of a brand new breadbin C64 from 1983....maybe one day I will do a video on what readily available item will do that :)
4.7uF ceramic? Where were you supposed to find one in 1982? Of course it was tantalum. I also wouldn't really be inclined to put it back in after pulling it out, i mean, it has been previously stressed.
@@NoelsRetroLab I don't know if you read my previous replies, but I was talking BS. The 6510's 16 bit address bus can only address 64kB at a time. So if you want to use more memory than 64kB at a time, you will need to add a separate bank of 64kB and a bank switching circuit which will need a dedicated CPU line. It will probably also introduce latency on the memory and require a lot more memory read and write cycles.
Is it only me that clicks first on the "thumbs up" and after that watch the video?. Noel is definitely underrated. He should have at least 2MM subscribers...
@@NoelsRetroLab When I'm "on fire" mood after watching your videos (anyone though), I press the button an odd number of times normally close to 31, avoiding to wipe the "like" :-DDD
I think it depends on the computers. I think on PCs that's more common, but most of the ones I come across (and the ones that fail over time) tend to be blue.
I've seen them all colors. I've worked in electronic manufacturing. They can have defects such as markings being reversed. But that's like 1% of them. The primary reason they're used besides size is that they're physically smaller than an electrolytic and presumably won't dry out over time.
Not this one. This is a 100% exact copy of the original board. There are other projects that are taking the route of copying it but adding modifications like you suggested.
@@NoelsRetroLab I watched the rest of your video and man, that was interesting to say the least. You've got me excited for commodores and im hoping to build one just to play around with it. Good content man!
Originally I was planning on making a single video about it, but that last bit took a while and was really interesting, so it deserved to have a full episode dedicated to it.
Thank you and welcome on board! That was one of the first retro t-shirts I got many years ago. I think I got it randomly searching one of those t-shirt sites like Spreadshirt or something like that.
4:55 watch the filament in the fuse bend when it goes boom!
Oh wow!!! Good eyes. I totally didn't see that until now. Good thing I stopped it when I did!
I didn’t notice that before. Wow! Great catch!
@@damianvila When I first saw it I was like.... "Did that fuse just say Hnnnrrgghhh!!?"
@@preferredimage Ahahahaha! Absolutely. You made me laugh. :D
These Sixty Clone boards are works of art. That you can buy such a nice board for $40 US is a testament to how far PCB manufacturing has come. 10 years ago I paid $1500 for a 4 layer board as big.
Absolutely!
Should have tested that capacitor, it may be all over the place after being reversed, and I wouldn't trust it further than a throw into the dead parts bin
Yes, it should just be replaced straight out. Good point.
@@NoelsRetroLab Tantalums especially. Once you heat them up or break down the oxide layer they are time bombs just waiting to short dead solid. Tantalums had much lower ESR than aluminum electrolytics in those days, and nothing else in the same size range had the same capacitance if you wanted 1uF or more. These days just replace it with a low-ESR electrolytic.
@@lwilton The beloved flame emitting capacitors :-)
@@lwilton or a MLCC, those have excellent performance as well.
Yellow/orange Tantalums are actually quite common - at least on PC hardware (which I deal with a lot). Usually they blow up spectacularly when you mess up polarization but I guess the voltage in this case was just too low to provide proper fireworks. Actually Adrian Black had a spectacular one blow up in his digital basement in one of his recent videos.
Haha, yes, I just saw it!! Probably because I work more on older computers, I tend to look out for the little blue caps, but you're right, they can be any color.
The tantalum didn't explode because PC power supplies can supply more than 10A and 7805 only 1.5A
@@VladoT I've seen a 1A rated 7805 deliver 3A for a few seconds before exploding itself.
Well worth replacing it as its been abused too.
I spent most of the day trying to get a PiStorm (I built from parts) to work. No luck, until a few minutes ago when I finally noticed one bad SMD solder joint. It's that breakthrough moment, that makes electronics fun.
That's right. It can be a bit like old games: the longer you bang your head against the wall, the greater the reward when you finally figure it out 😃
I totaly agree. You feel like you could rule the world. :)
I had a game I just couldn't beat. I got so frustrated I that I disassembled the ML and reprogrammed it so I'd win! Take that game!
Old or new, the diagnosis process is the same. Excellent as always!
Thank you! 👍😃
7:36 they used a tantalum because it has higher capacitance per volume than ceramic. If you look carefully at the schematic you can see that near the left capacitor is a .1 (uF i suspect) when near the right capacitor is a 4.7 (uF again i think).
Nowadays they are all yellow (including SMT packages).
Ceramic now include higher capacitance values but I would not be surprised if in the 1980s there were not.
Also in this case the tantalum is used as an energy reservoir rather than decoupling (that’s a job for ceramics) so that if the voltage were to dip for some microseconds it would hold the voltage up while discharging. My guess is that a voltage dip would cause some kind of glitch, maybe some register losses of some kind
The Tantalum capacitor used as a low impedance Coulomb (Charge) bucket. They are often used on power supply rails that are a fair distance from the voltage regulator.
I was just about to write a comment to that effect. They have a nice low ESR and make good decoupling capacitors. They also really do not like to be reverse biased!
They're damned dangerous things particularly when becoming old or subjected to overvoltage where they can spontaneously ignite and launch themselves as burning fireballs!
Yes, the low ESR enables them to dump or build charge faster. Combined with higher capacity and better temperature and frequency stability than cheramic, they are a typical go-to for decoupling digital circuits.
Ceramic capacitors above 1uF start to be more expensive. Tantulums are cheaper at high capacities 1-100uF, after that electrolytics start making more sense
If I recall correctly, they're smaller than a ceramic for those same capacities too, because they're technically an electrolytic themselves (just not an aluminum, and either partly or wholly lacking aluminum electrolytic's "self healing" capability).
Back in the 90's when I was doing board level repair for GE I ran into this often as the boards were populated by hand and I got all the failed ones from the line.
Good Job, looking forward to the conclusion.
Right. That would be exactly the same kind of situation. That's interesting.
Noel, excellent troubleshooting of that board. I’m a relatively new electronics hobbyist and am always looking for tutorials that teach the logic used to troubleshoot electronics. This video presented your troubleshooting approach in a very clear and logical fashion. As such, it was one of the best troubleshooting tutorials out there for someone new to electronics. Keep up the excellent work my friend.
Thank you! I'm really glad they're helpful. I also learned a lot initially about repairing computers from some early repair videos, so I totally get it.
These videos from people like you, Adrian's Digital Basement, and Jan Beta (and others) REALLY contribute to the overall knowledge base that will need to exist as these machines fail. Thank you for that! It was much harder before RUclips videos from contributors.
Thank you! Glad you're finding them useful. I'm always honored to be mentioned in the same sentence as Jan and Adrian 😃
Even though I don't have a C64 (yet), I get a lot out of these diagnostic/detective videos.
Great to hear! 👍
Don't know whether you are aware, but there is a small rework required on that version of the board to fix where a misaligned via causes one of the cartridge port pins to be shorted to ground. Not sure whether that would cause the issue you are seeing, but it does stop a number of cartridges (including epyx fastload) working correctly until its fixed.
Yes, good point. Rob told me about it and I checked, but it was already fixed on that board. I didn't include it in the video to avoid confusion, but you're right that it could have been causing all sorts of weird problems.
A tantalum capacitor is used here because its characteristics are very similar to an electrolytic: high capacitance in a small amount of space, but unlike electrolytics you don't have to worry about them drying out over time. However, you still have a high ESL similar to electrolytics, so for decoupling power rails you'll usually run them in parallel with a smaller value ceramic capacitor to make up for that. That's exactly what's shown on the schematic at 7:25, you've got a 100n ceramic in parallel with a 4.7µ tantalum. Other chips only have the 100n ceramic likely because the amount of noise they would dump out the v+ pin is small enough that it doesn't need the extra farads.
I had exactly the same problem with an old Soviet calculator. After replacing all electrolytic capacitor it started up and then died in ten seconds. One capacitor was installed backwards...
Makes sense. At least yours didn't blow up either! 😃
Polar caps that have been charged with the wrong polarity, cannot be trusted anymore. Always replace.
Great work as always Noel! I'm not surprised the original owner was having trouble diagnosing this, I can't wait to find out the ultimate cause of all of these strange problems!
Thank you! I think you're going to like the root cause of the CIA problems. That's why I decided to save a whole episode for it, so I can take the time it deserves.
@@NoelsRetroLab Looking forward to it!
I love these videos. I appreciate a person who can start what might be a 5 minute adventure or a multi part series depending on how deep the rabbit hole runs. You make time to educate about what must be basic concepts for you with imagery in the midst of it all. Pure skill definitely is a thing but I think I appreciate the way you communicate making really daunting things so digestible. Thank you.
Wow! I just built a Color Maximite 2 and it had some tantalum capacitors. I had no idea they were polarised.. amazingly enough I had 3 soldered the right way around. Very lucky!
Wow, that was lucky! Depending in which part of the circuit they were, they could have exploded.
Also notice that electrolytic caps mark the negative lead, while on tantalums the positive lead is the one that is marked. Aren't standards wonderful?
Great video, really enjoyed it and looking forward to part 2! I have my own 8088 Clone PCB being made at the moment, so I'm going to be populating that with old chips soon and interested if I have to go thought a similar journey of how to fix something that never worked in the first place, fingers crossed....
Thanks! Glad you enjoyed it. Good luck with that build. I also have an 8088 kit to put together at some point! 😃
@@NoelsRetroLab ooh would be very interested in your 8088 proj when you get round to it.
When building a kit, you don’t just solder everything in place, cross your fingers and expect it to work, instead you construct it in logical stages with component value checking as you go. For instance, initially assemble the power supply regulation circuit and check to see if it works, then progress to the next stage which might be installing any clock circuits.
True, that's probably a better way, but you need to be intimately familiar with the circuit itself to pick the right order and make sure you got all the components required up to that stage. I suppose a kit could provide those instructions, but most of the ones I've seen just have you solder everything, and at best, they'll provide some checks afterwards. I do like your idea though.
@@NoelsRetroLab Many thanks for the reply. Most kit instructions follow that lottery approach. I designed and built commercial prototypes from 1970's onwards for many decades where it was necessary to use an incremental approach. In the 70's through mid 80's prototype PCBs did not have solder resist so careful soldering was required to avoid unwanted short circuits. I do really like some of the modern mod kits that use bespoke flexible PCBs to replace bodgy wire connection to neaten their installation.
Hello Noel, nice video and good desdcription as to what is going on. Tantalum capacitors are used on power supply busses because they lossy and have significant ESR (
equivalent series resistance). This damps the bus and prevents oscillation. The regulator IC is basically a power op amp and is subject to stability problems if the output is shunted by a low ESR capacitor like a ceramic. The schematic you presented shows a ceramic and a tantalum in parallel which is good modern practice. IC manufacturers have papers explaining this and some of the data sheets also have explanations. I have also read an interesting paper showing the effects of various capacitors on the performance of linear regulators.
Interesting! Those details are definitely beyond my depth of analog electronics, so that's really helpful. I ended up replacing it with an electrolytic one of the same value. Do you see any potential problems with that?
Excellent video! I have one of the replica boards and everything to populate it. It's going to be a winter project and it will be interesting to see how many mistakes I make and need to troubleshoot!
How long did it take you to source the parts for it? (TBH I'd love to try doing either a C128 [what I owned growing up] or an Amiga 500 [always wanted one] )
Good luck with that! The hardest part is going to be getting the components (and trusting they work correctly).
I'm didn't risk to put same tantalum back.. Probably, it now has a minor internal damage and now it's just like ticking time bomb..
Great, that video chip was ok!
This will be interesting to see why ports is reported bad and what's causing it! 👍😉
Yeah, I'll replace it next time. Stay tuned for the mystery of the CIAs 😃
@@NoelsRetroLab Such a cliff-hanger! Is the follow up video out yet?
I would have replaced that tantalum...
Looking forward for #2.
The 7805 might have helped, but you're right, it's not a bad idea to replace it.
As soon as you had fixed the Tanty, you should have plugged it in to a TV to see if anything had changed. :)
Nah, I trust my oscilloscope to see that we had a black screen 😃 (actually, I think I did plug it in and it just confirmed there was signal but black screen).
The combination of the two capacitors should do the following: the 100nF eliminates the HF ripple, the tantalum capacitor intercept the pulse peaks. The ESR value is lower than that of normal electrolytes. In most cases, it can be replaced with a LOWESR electrolyte.
I would not leave the reverse polarity tantalum in the circuit because it may be partially damaged.
I had a non working parking remote, until I realized that it was just a free tin ball touching the frequency selector. How fun it is to troubleshoot
That would have been crazy! (unless you heard something rattling, that would have been an easy hint 😃).
@@NoelsRetroLab it was crazy, going downstairs to the parking many times.
I discovered it by cleaning the circuit. #be-noel-for-a-day
Bro you are an absolute mad lad. Your content is so fun and interesting to watch!
10 PRINT ''This channel is amazing! ''; : GOTO10
As someone that has worked with repairing electronics for 30 years myself, with a completely new board you cant even rule out that the traces are correct,something that you didnt mention and came to mind when you had the shoring problem of the 5 volt. I have personally had both shorts and breaks in the traces on new boards that the traces were supposed to be electrically tested on, not the most comon problem, but still. Great to see that there are people building these things, i still have an aoriginal breadbox Commodore 64 that i boight new back in the day.
Good point. I didn't go there because I knew that this board design was already tested and working with other people. But you're right that there was always the possibility of this one being defective somehow.
@@NoelsRetroLab Sure, but what i was talking about wasnt the design but rather the possibility of a manufacturing fault of that perticular PCB that you got in your hands, like i mentioned it has happened to me in some cases that one board out of many had faulty traces.
That tantalum cap that was connected backwards will have been weakened by that. I would replace it anyway even though it "seems" to be OK, and I would replace it either with an electrolytic or a ceramic. Tantalum caps are more trouble than they're worth.
Agreed. I'll swap it out as soon as I pull the board out again. I honestly didn't realize they would be permanently damaged, but everybody seems to be in agreement about that. Thanks!
@@NoelsRetroLab : The issue with tantalums is that like aluminum caps, they're electrolytics, so internal misconfigurations of the chemistry are caused by reversing their polarity (which is why electrolytics require a DC bias to properly handle AC uses). However, while aluminum electrolytics will _slowly_ repair themselves if subjected to a low current of the correct polarity, tantalums don't, and supposedly go through some sort of collapse cascade.
If you're going to swap it with a ceramic, just leave it out. Tants have different frequency response than ceramics do, so replacing it with another ceramic won't help. There's already a ceramic on that rail.
You really should have replaced that capacitor. Hooking it up backwards could have shortened its lifespan.
I think you're right. I didn't know about that but other people mentioned the same thing. Maybe the 7805 helped it a bit by shutting down, but you're right that it would be safer to replace it. Probably an electrolytic one would be fine too.
"They don' t make them as as they did any more". I am referring to the RAM chips and I don' t remember the correct punch line as well... 😉
They way they made them in the 80's was to buy defective memory chips for next to nothing, that could only address half their capacity, use the half that worked in each chip and mount double the number of chips.. Sinclair did this with one of their ZX Spectrum revisions. I think it was with 4164 chips, not sure
Or was your comment a sarcastic nod to this?
@@paulmichaelfreedman8334 I understand perfectly what you say and no, I wasn' t sarcastic at all. I just quoted the obvious: Somebody bought something in 2021 and it just didn' t work...
@@paulmichaelfreedman8334 You are correct, Sir; the first few revisions* of the ZX Spectrum 48K used those "half" 4164 RAM chips. The boards were designed so that by soldering in some jumpers, it could accommodate chips with either the lower half or the upper half working. Another set of jumpers allowed the use of RAMs from different manufacturers.
*Except the very first version; that one used a small daughter board that sat above the main PCB.
Amazing that the tantalum didn't explode! I've seen that happen too many times after applying reverse voltage even for just a few seconds! 😄
Seriously! It must have been a second away from a nasty surprise 😃
The value of that tant is 4.7uF (shown both on the schematic and visible written on the cap body)
You aren't going to find a ceramic with a value that large (ignoring modern surface mount MLCC caps)
It'll be providing a bit of local bulk capacitance for the VIC IC alongside the 100nF ceramic decoupling cap that's in parallel with it.
True. I don't know why I had it in my mind that it was 1uF, which would have been in the upper end for a ceramic one. So I guess the real question is why not use an electrolytic capacitor then. Were they significantly more expensive?
No idea about price differences back at that time. In that application I wouldn't have thought performance differences would be a factor.
Tants will tend to be physically smaller, but there doesn't appear to be a space problem - could always have used an axial elec. if there were height concerns.
Really easy to overlook it sat alongside all those resin dipped ceramics though (and the schematic not actually putting any units next to the value doesn't really draw attention to it either - it *could* have been 4.7nF - although that wouldn't make much sense in parallel with a 100nF decoupling cap).
I really enjoy watching the diagnostic process..thanks!
Great diagnosis job, really. There is a lot to be learnt from you. Looking forward to the next part!
I've built a sixty clone replica and it worked fine since the beginning (I was amazed to discover I didn't do any mistake, and even if I used jumpers instead of the ferrite stuffs, it worked -and works yet- flawless). That's the C64 I'm using habitually.
That's great! I'm still unclear why the original board is full of ferrite beads. I get what they do electronically (kinda) but I don't understand why they felt the need to use them everywhere. There are other computers of the time without a single one.
Always fascinating watching you troubleshoot these 'old' machines!
Glad you like them!
2:18 at this time is anyone else yelling “check that tant!”
Probably!! 🤣 It was right there in plain view.
Tantalums are usually blue? I think all the old ones in old IBM equipment are yellow.
I noticed that, too.
I have red, green, yellow, blue at hand. This is usually a color code for the maximum voltage of the tantalum capacitor and it is possibly manufacturer dependent.
But there is also a norm specified. Search for "Capacitor Voltage Colour Code Table". In that yellow is 20V and blue is 35V for Type J (Dipped Tantalum Capacitors).
Also: The reverse driven of the capacitor possibly has the electrolyte and foils damaged and it has a very shortened lifetime. It is better to exchange that capacitor with a new one.
That's what I'm hearing, especially PCs. The ones I encounter on the computers I repair are usually blue (like the original one in that C64).
Yes, good idea. Planning to replace it.
These detective / resurrection episodes are fantastic! Question / concern: When you changed the voltage on the RF module to +5 by unsoldering the pin and running a wire ... is there any risk of accidental contact of the pin still present in the unsoldered hole (perhaps by vibration if the machine is moved around)? Would it be appropriate to snip off the pin on the “bottom board” of the RF module?
Thank you! No, there's no concern about accidental contact. I actually removed the metal pin completely, so you're left with the plastic from the pin header separating the two solder points.
There's something incredibly aesthetic about 80s electronics. That specific tone of blue (or sometimes green). Maybe it is the text font on pcbs. The size of the components. Ahhh, I don't know. Excellent video. I think that Moore's law is about to reach its limit and we will be seeing more people getting creative solving problems with some vintage ideas. I don't know about using the RF out for monitoring though haha
I agree. I think a lot of it is also due to the fact that you can wrap your head around one of those computers intimately and figure things out yourself. Once you move into the 90s, things start getting a LOT more complicated.
@@NoelsRetroLab If I were a professor I would personally teach computer-applied electronics basics on old high level computers (C64, AMIGA, ETC.) rather than new low level computers (Raspberry, SOCs, etc). And yeah, I'm a 90s kid (not a kid anymore actually haha) and I remember the HUGE spike between pentium generations and how Windows XP was "impossible" to run properly. Such thing hasn't happened nowadays. And with the semiconductor shortage, the hardware spikes will get even slower. It sounds "bad", but is it?
@@tspawn35 Agreed. And also with this "circular economy" tendency today and the insane amount of electronic waste we do, there is a lot of good stuff that could happen. In my country, repair shops now only repair blenders, refrigerators and stoves. I have some broken LCD displays, fully functional CRTs, motherboards and Pentium 4 era hardware (PCI tuner cards, IDE drives, DSL Modems, etc) that don't have a "use" anymore but I just don't feel like throwing them away. As you say, doing board level repair makes sense as it is cheaper but I'm no sure if it is, you know, "marketable" for companies to let you repair your stuff :(
@@SUP3RP3DR0L1V3Was also thinking about the whole idea of how you might teach programming, and the vintage systems that have the OS baked onto the hardware (like the Commodore machines) also have another huge advantage--it's VERY hard to screw up the machine itself---e.g. a hard power cycle will put you back to a known good state.
Have you heard of a project called the Commander X16? This is a "modern 8 bit computer" based off the vic-20 architecture. This also got me thinking (and yes most of this is a pollyanna view :D )....once the CX16 it is released in kit form, would be some sort of "summer program" that would teach both the lower level programming and practical soldering/electronics.
The idea is the students would either start on the emulator, or physical CX16s to learn the coding, but along side of this, they would also learn practical electronics/soldering/debugging as they assemble their own CX16 from kit.
At the end of the program, assuming things went well, they'd end up with a fully functional "modern vintage computer" that they get to keep
@@artstrutzenberg7197 I'm an IT Engineer personally and only took a small subject on electronics at school (my university had a totally software-oriented curriculum, maybe some networking over here and there). I learnt to understand high level programming languages just by practicing and not reading theory or the principles behind it (it was cool at the beginning). But just when I thought I was a prodigy, I got hit in the face by some OS scripting problem on Linux (due to PTSD, I rather not remember what it was haha). Programming logic at OS level (C modules on linux) is a WHOLE WORLD different to what I do at work as a Web Developer. From there, I started to try to understand the "low level" under the iceberg but that led me to needing to understand (and I mean understanding, not what I used to do back at school :P) math (discrete math, algebra, calculus, numerical analysis) and electromagnetism and optics (physics). At the end I ended up here, talking about electronics which is the basic form of modern computing. So, if you look at it, I did everything that was needed but in the opposite way (Frameworks -> high level programming languages -> operating systems -> electronics -> basic sciences). The way I did is a very good way of keeping interest on the students, but a terrible way to actually understanding stuff. So, you should go step by step of technology (Basic Sciences -> Electronics -> Computers -> Low level Programming languages -> Operating Systems -> High level programming languages -> Modern Technologies). Commander X16 as a project or even as a whole subject to study on the first courses (if not the first one). Keeping your first computer is a literal milestone hahaha
Left on a cliffhanger!
A little bit 😃 But at least all the major problems were solved before that.
@@NoelsRetroLab It sounds like the most interesting one is still to come though - looking forward to it! :)
Can't wait for Pt 2!!!
Wrapping up the edit right now, so hopefully in a week or two.
Before you waste too much time on that cassette port, make sure it's even supposed to work. I had thought on the new C64 boards the cassette port wasn't 100% compatible.
A tantalum capacitor as more capacity than a ceramic capacitor. They are always used in tandem because the ceramic capacitor as a fast transient response the tantalum does not have.
Woo hoo. Well done Noel! Hanging out for part 2.
Editing it right now!
You should also take a look at Adrian's Digital Basement
About his tantalum explosion? Adrian's is one of my favorite channels! 😃
A great video with an interesting topic. I'm owning a c128 with keyboard and system pcb problems. I was already sneaking on the web site of the builders of those pcbs. They have a new 128 pcb too. I will use your excellent video as guide. Top diagnostics time!!!
Oh I didn't realize the C128 was already available. Maybe that's how I'll finally get my hands on one! 😃 Good luck with the build!
just started the video... i built some thing like this and out of the 100 ceramic caps i put in 1 of them had a short.. what a nightmare...
Ugh. That's bad luck. And the worst thing is that resistance checks wouldn't work because all decoupling capacitors would show up as shorted. Did you have to desolder them all, or did you track it down with sensitive voltage measurements?
Very interesting diagnostics on the board, super nice board, ive considered getting the C128 version and retro fixing an old 128, could be fun. Great video!
Lol "they are usually blue" - nah in all my years I've seen more yellow tantalums than any other colour. A 4.7uF tantalum is / was cheaper than a ceramic back then for similar performance. I would have thrown that capacitor away, tants have tantrums (boom tish) when hit with reverse polarity.
Yes, I hear on PCs are mostly yellow. Not sure why, but in most of the computers I work with they tend to be blue and my eyes are trained to look for them (especially because they short with time).
Can't wait for the next video seen some problem solving I haven't seen before
Thats a nice looking board :) I also made some "new" boards, but for Apple Lisa. Creating replacement PCBs is pretty simple these days.
Very nice and instructive video. Thumbs up.
I'm already in a 'drooling to see part 2' mode :-)
You're welcome. I'm editing part 2 right now, so it's coming soon! 😃
Great Troubleshooting video. I am wondering if the Retro Chip Tester would have caught any of these problems?
Hey Noel, when the CIA has no order they will do strange things.
Now I have learned new things about tantalum capacitors that I don't expected. Thank you very much.
You're welcome. The CIA problem runs much deeper than that. So much so that it deserved a whole episode to itself. Stay tuned.
4.7uF - 10 uF tantalum capacitors were very commonly used for power filtering in 80's-90's designs, and in fact they are still being used. Higher capacitance MLCCs were not available back in the day, and even now they have some drawbacks, for example their capacitance goes down significantly when the voltage is applied. BTW, I am curious what 8088 board do you have. One of my designs?
That makes sense. Is there a reason to use tantalum over electrolytic in that case, or is it a perfectly fine substitution in that case?
And yes, I believe the boards I have are designed by you now that I think about it! 😃 I've had them for a while, but I'm hoping to do the build sometime soon. Thanks for making that project. It looked amazing!
@@NoelsRetroLab : Lower internal resistance & inductance, which are usually both good.
@@NoelsRetroLab tantalum have better filtering characteristics at high KHz to low MHz frequencies - ie exaclty the frequency area that the buses would be operating at. Ie better at filtering any noise induced on the supply by normal chip operation.
Great video i plan to assemble one of these boards .
Good luck!
Often times tantalum capacitors are a better choice in old digital circuits because they have lower ESR, probably why they were chosen.
Tantalum caps are supposed to provide more stability at least in PLL circuits alternatively you could use a film or ceramic in place of it
I cut my 8-bit teeth on the Commodore 64 (with a special mention to the Atari 400 which was the first micro I owned). Those 8 bit machines were powerful enough to be interesting, and also simple enough so that a properly obsessed school child, armed with the provided documentation, could suddenly find themselves a budding computer scientist, with WarGames on the big screen to let us know the magnitude of what was coming. If you're a very young person seeing this video, know that the Commodore 64, first among equals of the period, was an absolute game changing personal computer, and many of your favorite games were probably contributed to by programmers who had learned the core, really important, lessons of computer programming on computers of just this type. Also, it wasn't even a "weak" computer. Color hi resolution high speed graphics (faster than the human eye, anyway), great sound synthesis, a peppy clock speed. Once you owned a machine like a Commodore 64, even as a child, and had read its operating manual, it was manifestly obvious that if you could master it, you knew what a real, powerful computer truly was, and that everything that would come after this would just be more of the same, better to be sure, but only quantitatively, not qualitatively, in accordance with Alan Turing's 1932 epiphany that, deep down, there's only one kind of thing anyone that can make that should bear the term "computer", &c.
My A500 conked out in '91 , it just went black. When I removed the keyboard, it worked fine. The tantalum cap on there had suddenly decided to die.
That's another problem with tantalum caps: They seem to short with time. Not a fan of them.
@@NoelsRetroLab I read here and there that tantalum caps should stay stable longer than ceramic caps, so I guess it's down to quality. Commodore (among many) wasn't above buying inferior components to cut cost.
@@paulmichaelfreedman8334 : Perhaps they stay more stable in regards to e.g. temperature, but past a decade or two I'd expect the tantalum to be worse, because they're a type of electrolytic cap that lacks the self-heal capability of aluminum electrolytics.
Although it was not the problem, I thought that maybe it could help someone else, who knows. What I was thinking right away was “oh maybe the backplate of the regulator is not to gnd but it is a vout pad” (although i think it would have just blown the fuse). But it could be an error that some non-experienced person could do. So maybe some ebay regulators or the wrong package can really cause problems if you are not aware of the fact that the back plate on those can also be Vin or Vout other than GND. I don’t know, I thought I should share it. Let me know if you think it might be helpful or a totally useless comment
NO - You do NOT put back in a Tantalum! - They are notoriously for blowing up - especially after having been stressed!
Yes, I didn't think about it at the time, but that's a good idea. Fixed and I'll be following up on that next week.
Its beter to replace the tantalum cap which was reverse polarised.
Its damaged for shure, its just lost the most of its service life.
Since they love to go short and burn...
They are used since they riple smoothing is ten times beter then standard electrolite ones.
Have you created the video that shows what the problem was with those bad chip error messages? I was thinking about getting one of these boards, but after your video I am not so sure. Would really like to see how it all turns out. Thanks.
7:21 they didn't have 4.7 microfarad ceramic capacitors in 1986.
At least the tantalum didnt blow up as Adrians (Digital basement) did =)
Maybe it would if you left it on longer..
Right!! I think it was the 7805 that saved me because it shut down as soon as it started getting hot.
Yeah, I suspect it was on a countdown to detonation. Tants do not like to be abused.
I would not mind building a modern C64 PCB, but the cases are hard to find in my area. Could I build them inside a Vic 20 case?
You’ve made me feel like a trout…hooked!
As long as that's a good kind of hooked, it's all good 😃
Definately replace that Tant! I was a little jaw-dropped when you just turned it around, after it had been reverse biased and had been sinking so much power! ie. It should no longer be trusted. Just say'in. :-)
Yeah, that's the plan! Thanks for the heads up.
you have the best channel over the web!!!!
Weird, I thought these Tantalums, once they start to short (for whatever reason, not just by being in backwards), they're toast. (although I had that happen to high voltage electrolytics - and after putting two of them in backwards I started triple-checking and guess what - I managed to put another one in backwards anyways)
You may be right about that. I didn't know that but other people pointed that out. The only thing I can think of is that the 7805 shut down faster than the cap was damaged. Alternatively maybe the cap was damaged but since it's just a decoupling cap, we can't really tell anything is wrong. Probably safer to replace it though.
Noel, probably I am wrong, but... at least it seems when you finally checked out the test with warning on cassette that the cassette cable is actually not very well inserted. That could be an explanation about why when you replaced the 2 "wrong" ICs still the same mistake, same point but this time only 1 is showed as wrong IC. Does it make sense?
The CIAs are both reported as faulty, independently of which ones I put there (it just takes another pass for the second one to be reported). The cassette part... I did show up as faulty and that just went away. I thought it was because I cleaned up the edge connector, but maybe you're right and it just wasn't pushed in all the way.
@@NoelsRetroLab I think it is a remote possibility, :) and maybe you will find the right issue in the next episode!!!! :)
A tantalum cap that has been connected in reverse, especially one that has already shortened, is utterly destroyed. Flipping it is a *bad* idea.
NEW CIA, VIC-II and SID replacements are also really important.
Right! Working on a SID-replacement comparison episode at the moment. Coming soon! 😃
@@NoelsRetroLab Yeah, I saw a recent video with an FPGA SID playing Lightforce tune and it sounded OK at the bit near the end where most emulations fail. Not sure on the state of VIC-II direct replacements. CIAs are less important for now and most of the other chips are no problem as far as I know. Of course you have to recreate the exact smell of a brand new breadbin C64 from 1983....maybe one day I will do a video on what readily available item will do that :)
The tantalums on my BBC Micro are all yellow. You can only tell them apart because they are taller. My next job is to replace them all.
Holy smokes, I just realized that Noel and I are wearing the same t-shirt. :)
It's a fantastic shirt, so that's only natural 😃
4.7uF ceramic? Where were you supposed to find one in 1982? Of course it was tantalum.
I also wouldn't really be inclined to put it back in after pulling it out, i mean, it has been previously stressed.
Dude you don't place the same capacitor that was installed in the wrong position! That component is damaged!
I'm a bit surprised that it didn't lose its top. I have seen them leave spectacular smoke trails!
Loving this series! Looking forward to more. Cheers Noel
Glad to hear it!
Other than cost, there is no reason to put a tantalum cap in this situation.
Right. That makes sense. Thanks!
would be nice if they incorporated 128kb or even 512k in to the C64.. if your respining the board what is stopping you?
That's the next step: Enhanced replica boards. This particular one is an exact copy, so I don't think it can be easily changed.
@@NoelsRetroLab I don't know if you read my previous replies, but I was talking BS. The 6510's 16 bit address bus can only address 64kB at a time. So if you want to use more memory than 64kB at a time, you will need to add a separate bank of 64kB and a bank switching circuit which will need a dedicated CPU line. It will probably also introduce latency on the memory and require a lot more memory read and write cycles.
@@paulmichaelfreedman8334 And completely customized software to use it. You can't just add bank switching in some transparent fashion.
@@stargazer7644 indeed. Probably the reason why nobody bothered in the first place.
6:55 "..this going back in..." - what ? What are you doing ? You must replace it immediately, it's probably a damaged capacitor, very cheap too !
I have to say the good things too. Your channel is really awesome.
It makes me feel nostalgic for my youth. And I feel old, meh.
I know, I know. I wasn't thinking. That's replaced and I'll go over that on next week's video 😃
So educational, great video, thanks! :D
Glad you liked it!
Is it only me that clicks first on the "thumbs up" and after that watch the video?. Noel is definitely underrated. He should have at least 2MM subscribers...
Thank you! 😃 Although if you click twice the "like" goes away 🤣
@@NoelsRetroLab When I'm "on fire" mood after watching your videos (anyone though), I press the button an odd number of times normally close to 31, avoiding to wipe the "like" :-DDD
Usually blue? All of my tantalums are yellow or orange.
I think it depends on the computers. I think on PCs that's more common, but most of the ones I come across (and the ones that fail over time) tend to be blue.
I've seen them all colors. I've worked in electronic manufacturing. They can have defects such as markings being reversed. But that's like 1% of them. The primary reason they're used besides size is that they're physically smaller than an electrolytic and presumably won't dry out over time.
I believe capacitor types are oven chose for their frequency sensitivity characteristics.
Tantalums can be yellow.
I hope, the replica has modern connectors for peripheral devices.
Not this one. This is a 100% exact copy of the original board. There are other projects that are taking the route of copying it but adding modifications like you suggested.
Great vid. Thanks, Noel!
is there a second part of fixing for this board?
Or... it could have a broken trace. I had that happen to me once and I was astonished. Ordered a new board and it worked like a charm!
Not in this case. The problem was subtle and malicious.
@@NoelsRetroLab I watched the rest of your video and man, that was interesting to say the least. You've got me excited for commodores and im hoping to build one just to play around with it. Good content man!
What you've be sayed if that tantals was misreversed in the controllers on the giant chemical industrial plant?
enjoyed this eppisode im looking forward to the next one on this should be cool thanks
No no no no, you can't stop now!
Originally I was planning on making a single video about it, but that last bit took a while and was really interesting, so it deserved to have a full episode dedicated to it.
Just subbed. Great video. Where did you buy your Commodore T-shirt?
Thank you and welcome on board! That was one of the first retro t-shirts I got many years ago. I think I got it randomly searching one of those t-shirt sites like Spreadshirt or something like that.