Every Retro Computer Is A Ticking Bomb
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- Опубліковано 13 лют 2024
- You know the feeling: After not using a retro computer for a while, you pull it out of storage to use it and... it's not working anymore!
So let's fix it. Or try it at least.
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Something to watch out for: around switches and power supply connectors cold solder joints. Anything else that has stress placed on them are candidates for this problem.
Old field tech here.
From my own testing, I have a rule of thumb that the old potted C64 linear bricks "should" be outputting about 5.1 to 5.15v unloaded, while modern switching supplies "should" be about 5.2 to 5.25v, because the voltage drop on the modern supplies is greater. If you see an old C64 brick above 5.2, that probably indicates it is creeping up as it ages, but is completely normal with the new ones. It's also good to see Electroware chiming in about their product in the comments. Their PSUs are my go-to modern replacements and I've found them to be very good, but as the maker mentioned, you've got an old model there. The new ones output less voltage on the AC line (about the same as Commodore's originals), and some have a tuning adjustment so that you can achieve exactly 5v on your own particular C64. -- JC
Noel has the oscilloscope on the shelf and not using it for testing PSU. What? Did he buy DSO just for decorating purpose? I had one PSU which showed 5.1V on multimeter while on scope there were nasty 11V spikes clearly indicating failing PSU. Always use scope to see how clean and stable PSU output is (especially when you have one on the shelf).
Ask Adrian Black for the character issue, he had exactly the same thing in one of his bad c64's.
The one with the screen of random characters? Mine was just like that when the original potted brick that came with it went out. 8 new 4164s and a new aftermarket supply fixed it.
I had a known "good" power supply work with my C64 setup, when I started testing other 64s they gave black screens mostly, a few gave garbage. At the time I thought I had a bunch of bad SIDs, VIC-II and a bad Character ROM. While re-testing I noticed the chip I thought was bad worked on another unit. So I replaced the power supply. Suddenly all the chips worked. While the power supply put out a safe 5V, it dropped under load. Some C64 seem to draw more current than others. My usual C64 did not draw enough amps to cause the failure, but adding some other chip that did draw more current killed the 5V.
Well... it seems to be a very old PSU from Electroware (4 years old) and it's not longer in production for years - as it was replaced with two or three new generations. Now we are using totally different transformers giving much less voltage on AC line (~1.5V less) and... the 2x5VA does not mean 2x5 Volts :) but 2x5 Volt-Amperes (similar but not same as Watts)! Here is the definition: both watts (W) and volt-amperes (VA) are units of measurement for electrical power. Watts refer to “real power,” while volt-amperes refer to “apparent power.” Usually, electronic products show one or both of these values to provide information about how much energy they will consume or how much current they will draw. Each of these values can be used for various purposes. Volts times Amperes (VA) is used instead of Watts in direct-current systems but when dealing with alternating current, if you introduce a reactive (non-resistive) load, Volts and Amps are no longer in phase and trigonometry enters the equation.
If it comes to DC part: 5.20VDC on 5VDC line is absolutely normal and desired in this PSU project. Current draw of regular C64 system will cause a voltage drop on 1.8m long output cable, DIN connectors and C64's power switch. PSU is factory calibrated to give exact 5VDC (near to 5VDC) when used with C64C(we have used C64C as a reference as it's most common model). Voltage should be always measured on C64 mainboard not at the DIN connector with unloaded PSU.
If you have more questions don't hesitate to ask. Best regards: Andrzej
www.C64psu.com
Correct me if I am wrong, using big honking transformers is way less error-prone compared to a switch mode power supply. But you are somewhat reliant on the quality of the transformers, since they seem to be sealed units.
@@OscarSommerbo Only one of these units is a transformer (the bigger one - for 9VAC), the smaller "brick" is a complete mains-powered 5V switchmode power supply.
I would also add, correct me if I'm wrong, the main reason why there is a power switch on the PSU itself is to allow the user to not touch the power switch on the C64 as these are prone to failure as we all know.
@@daghtusThe main reason is, that the power switch on C64 does not turn off power from the PSU, so it is running all the time, as long as it is plugged into the socket. This wastes energy, produces heat, and causes excessive wear of PSU components.
CTRL-9 will turn reverse on from the keyboard in the editor, and CTRL-0 to turn it back off. Then you can just type to get reverse characters. CTRL-1 through CTRL-8 and C=-1 through C=-8 change the color of the text.
I'm not sure if I ever saw an AC power supply that is outputting exact specified voltage. All of them are way higher. Even original Commodore one is outputting like 11V
I had a similar issue with PSU's with a C128 I was trying to repair. I chased my tail for a month trying to track down an intermittent fault when powering on and for the life of me I couldn't figure it out initially. If I immediately turned the C128 off and back on again it'd usually work... sometimes. From all appearances it looked like either the 8502 or Z80 was bad.
Turns out it was the new modern PSU I was using.
What made it even more difficult to track down is that the modern PSU worked fine on several other C128's I own, but on this specific unit the 128 just didn't like that modern PSU at all. You name it, I did it to this C128. Recapped, changed voltage regulators, changed chips (ex: the 8502, CIA's, ROM chips, etc). Replaced the modern PSU with an original and it's been working fine ever since.
I remember there was a video that I think Bil Herd put out that went into detail that the older systems just don't like the new switching PSU's out there and how getting the old analog stuff is becoming a problem (it was a talk at a VCF if I remember right).
What made me think of this when I watched your video is that your modern PSU and mine use the exact same Mean Well DC switching power module inside. I haven't checked this myself on mine but I'm willing to bet that if you attach a scope to the DC rails while powering on the computer you'll see an excessive voltage drop before it finally stabilizes. That's just a hunch on my part though.
"Mad" Jack Tramiel always built computers as cheaply as he could.
I've been fascinated watching this because I've recently learned that I'll be getting my old Atari computers back from my brother-in-law who took them when I moved to California thirty years ago.
They all worked fine when I last saw them, but that was a long time ago.
I had a late-model Atari 800, a used Atari 400, and a used Atari 1200XL, along with assorted disk drives, cassette drives, printers, and controllers.
I'm looking forward the getting them back, but I'm concerned about whether they still work or not, and what it might take to get them working. I like each of the three machines for different reasons and I really want them all to be working.
But forty years is an awfully long time for a consumer computer, especially an early one.
Power supplies, it has nothing to do with Europe or North America nor their voltages. The 7805 regulator used in those bricks are under-cooled and over worked. Their failure point is usually the negative terminal blows internally to the regulator and the voltage spikes. Commodore covered the components (including heatsink) in a block of epoxy with no way for the heat to be dissipated. It is inevitable for them to fail. They are all ticking timebombs. The 7805 is a great part when cooled properly. When it is not cooled properly, all bets are off. It was an act of stupidity to entomb the regulator and heatsink instead of making the heatsink larger and exposed to ventilation.
Yeep! It didn't take many years of use until my potted beige wedge internal 5VDC gave up. I placed a new 7805 on an external alu heatsink and patched wires back inside. While at it I put the entire PSU on 20mm stilts to allow airflow under PSU as it spend most its youthful days on fuzzy carpet. The 1541 drive also got scorching hot so I placed a fan inside it early on.
I thought it was a 3052P instead of a 7805?
@@mikmurphy1 I for one have no idea, I never bothered to exhume the enclosed regulator. I just grabbed what was available. Paid no attention to load line behavior 😂 I wasn't that well versed in electronics... Uuhm 37 years ago or something.
@@mikmurphy1 That is a high possibility for some bricks. However, it doesn't matter which part it is. The introduction of epoxy completely eliminated any ability to radiate heat from the chip.
Hi, when you check a power supply, you should also check for ripple on the DC level. You are not likely to notice a ripple when you measure your DC voltage. Check it with a scope, or put your meter into AC mode and see if you measure any ripple on the DC output. Noisy power rails or high levels of ripple can cause all sorts of faults on digital circuits like odd glitches, random resets etc etc. Don't assume because you read the correct DC level that there is no nasty ripple there also. Especially when you have random results at power up.
I've kept my vintage PCs in a heated storage unit or in my apartment and I've rarely had any problems.
This happened to me as well, the kernal rom chip jumped off the socket (less than 1mm), most probably during moving. Reseating helped.
That's what sucks about old computers: they get old, and so does everything in it that makes it work
The modern power supplies all seem to be hit and miss. The keelog outputs a fairly high AC voltage under load, and it seems like the electroware does the same. And it looks like they both use the same meanwell module for the 5VDC. The problem there is while the C64 does have an LC filter on the power input, it probably wasn't designed to filter out modern switching supplies. Some of that noise will make it's way through the entire system and can even be visible in the video output.
The only one I've heard solid positive reviews are Ray Carlsen's offerings, but I hear he may be retiring. The other option is DIY, but you'd probably want to follow Commodores design and use a linear solution. In that case you may as well just use a Commodore brick and a power saver if you're worried about it going over voltage.
It may still be worth cleaning or replacing the C64 switch. A simple way to rule out the switch causing issues is just to bridge middle and lower pins on each side the switch itself, effectively hard wiring it ON. Then do a few tests unplugging and plugging in the power supply to see if it boots properly, if it does then suspect the switch, if not suspect the power supply
Yeah, I was afraid that the switching one would introduce noise. I see that quite a bit with Amstrad and ZX Spectrum (and sometimes you luck out with your PSU/computer combination). I'm pretty sure the switch is fine and it works 100% reliably with the other PSU. The whole thing is a bit weird.
You are right. I have built 2 different power supplies (not a big deal, one AC transformer, a fuse, and one AC->DC 5V module in a box) and one of them gave such bad noise to the video output I could not read the characters (for quite a while I thought that the video cable caused it). The other one (with a smaller, black, potted 5V module) is perfect.
Fun fact these machines will run (not reliably) at 3.5v. When I made my PSU I was having issues, but I couldn't trace it down at first. Turns out the cable was too thin and didn't carry enough current. It was running at 4.5v normally, but only about 3.5v with my U2+ cart. 4.5v SHOULD be enough. 3.5v is not. After I replaced the cable with a thicker one, all my problems went away.
The petscii character set is divided in two parts. 0-127 are the regular characters, while 128-255 are their reversed versions. The only difference between a regular character and a reversed one is the last bit. Maybe you have a problem with a trace or a connector for the 8th bit of the character ROM? It wasn't clear in the video, but does the glitch look like parts of the characters flicker from reverse to regular, or is it only garbage?
Still watching the video, but the voltage runaway definitely affects European PSUs as well, I had a friend who had his childhood machine almost completely fried by one like two TTL logic chips or something survived, everything else was gone. So I wouldn't take the risk.
The VIC-II has very little to do with the reverse characters. Reverse is not done in the video hardware, but by the definitions in the second half of character set, characters 128 and up. (They all have bit 7 set.)
I would suspect a bad character ROM first and swap it with a known good one to rule it out first. Otherwise something that would affect bit 7 of the character codes, such as an address line to the character ROM or possibly D7 to the VIC-II. Possibly the PLA as well, as it is between the VIC-II and the character ROM. (Could also be a ram chip or anything else connected to the data bus that would pull D7 low intermittently, although I can't imagine a failure that wouldn't also corrupt the data read by the CPU and cause crashes...)\
If a game that uses a custom character set doesn't have this issue I think it points pretty strongly that it is the character ROM, or possibly the PLA.
A very interesting test would be to copy the character set to RAM from BASIC and switch to it and see what happens. My guess is there will be some corrupted characters but they will not flicker and change.
I had a C64 ROM fail, so that it caused every RAM address location in BASIC RAM
ending in HEX 0D to either add or subtract 1 from the stored value, depending on if
the RAM address was odd or even...
That forced me to do a NASA work around and learn to write machine code in the
unaffected RAM addresses...
The flickering reverse character issue has to be the CHAROM or a trace to it. A11 selects upper/lower character set and A10 selects inverse video. A9-A3 is the character and A0-A2 is the row. CHAROM is addressed by the VIC through the 74LS373 at U26 for A0-A7 but directly by the VIC for A8-A11, so it's not U26.
We know the VIC is OK because dead test uses Ultimax mode, so the CHAROM is banked out and $F000-$FFFF of the cart ROM appears in VIC memory at $3000-$3FFF. The row of colors at the bottom of the dead test screen are inverse spaces and they were not flickering.
I put heat sinks on the precious C64 chips. I don't know if that helps or not, but I like to think it does.
Some modern PSUs use a switching PSU from companies like MeanWell to generate the 5V and a good old transformer to generate the 12VAC. I've had a couple of MeanWell PSUs fail on me over the years. They all have a pot on them that will allow you to dial the 5VDC level if you feel it's too high.
Are you sure it's going to be the VIC and not a problem reading the char rom with the high bit set?
dead test is mostly to get you up and running at all. The diagnostic cartridge can test roms. It's much more detailed, but requires a harness for best reuslts.
13:44 no, it's rather a switch. in 10 power ups it gives 5 OKs, 3 blue screens and 2 no LED. Yet you've measured it once and called a day. Worn out switches tend to be flaky to sat the least, but there's nothing that couldn't be fixed with contact cleanser and/or ultrasonic cleaner:)
I've started storing spares as a result
As you found without the basic rom you will just get a blue on blue screen. As it only works half the time it may just be a bad connection on the socket or EPROM adaptor. Not sure about the inverse characters, I wonder if that's just a similar connection issue with the character rom. Anyway, I'm sure you'll figure it out and if you need some neat rom replacements, I know a guy 😉
I didn't specifically check the contacts since I put that socket myself just a couple of years ago (I think anyway). But I should if it happens again. Happy to get rid of the socket adaptor monster anyway. And if I need to, I'll definitely hit you up for some replacements. Thanks :-)
I was having a similar thought with the BASIC ROM chip, in that perhaps it was not bad, but just needed reseated. It might be worth testing that chip in another board.
Bursting/leaking capacitors or clock batteries are also another big problem with old computers. They leak and destroy traces on the motherboard, or worse. But to be fair, it's really too much to expect a piece of technology to last beyond 40 years, especially these old motherboards, so I cut them some slack.
I bought a CPC 6128 recently, your right it's an amazing 8bit computer. Very happy with it.
you're
Grammer troll.
Really enjoying these simple let's take a look repair video here, thanks for sharing. I know nothing about C64 apart from watching a tonne of YT videos on them, so no ideas from me 😂
What I love are “Walking Shorts”:
I got an old Intel Retro PC. Before I tested it, I checked all the Caps on the MoBo, GPU, Sound Card and PSU - everything was OK!
So i plugged it in, started the PC and POP - PSU Magic Smoke...
I recaped the PSU, turned it on and POP - Mobo Caps...
This "Short" traveled through the entire PC to the Sound Card.
What was the Cause? No idea!
sounds like that PSU took the mobo with that. i generally avoid many old PSUs like the plague
Tantalum capacitors are notorious for testing absolutly fine when you do your shorts test out of the box ,, them dead shorting and blowing stuff up the second you apply power. The tantalums on +12 volt rails are the worst offenders , but I most deffnitly have seen electrolytic capacitors go bad with age and short or go very high ESR as well ..
The modern power supplies are always going to analog transformers for 9v line. 5v line may use a switching regulator rather than LM7805. All my C64's are using original PSUs.
About 4 years ago I repaired 4 computers with black screens, then I wrapped and boxed them. Who knows what's happened to them since. 🤔😀 Maybe I should have sold them.
A working Commodore 64 is only *slightly* more useful than a dead one. The low-resolution display would drive me crazy.
"Sometimes the LED light doesn't come on...."
Power switch. That's my immediate first thought. Let's see if I was correct.
EDIT
I wasn't correct, but it is still a common enough issue.
Nope, I thought of that too. It looked pretty good. Check out the followup video coming up in a couple of days. I look at that delay a bit more closely.
The glitchy static on the inverse characters sounds like a (video) memory issue. Maybe an address decoder circuit, or down wind of it, before the actual video generation circuitry, or the Vic II. Just a guess.
Hi, is the blue case a 3D print or painted?
I've actually never had that happen (yet). But I sure have bought a lot that were previously screwed up lol
I bought a Spectrum+ a couple of weeks ago and still haven't powered it up because I'm waiting on a new power supply (instead of the original brick that came with it) so I am now feeling a little bit more justified in my caution.
I wouldn't be too concerned about the original Speccy PSU - it's just a 9v brick. Completely unregulated linear supply, just a transformer, rectifier and smoothing cap inside. There's a 7805 regulator inside the spectrum itself that generates the stable 5v from that, so it won't be too fussy about input voltage, anything from 7.3 to 35v will work! That said, best to keep with a low voltage like 9v, as the more voltage you put up that 5v regulator, the hotter it gets, and I seem to recall that was already a perennial problem with old spectrums...
The Commodore 64 in my experience over the years is one of if not the most unreliable vintage machine you can own. Not saying that other old machines will not have failures, but this machine has been the most problematic over the years for me. Multiple machines, many issues. Some resolved, some never resolved. I only resolved my issues entirely when I built a clone C64 and populated it with nearly all new modern replacement parts. Yeah, I went that far in order to obtain a functional C64 that was reliable.
I don’t mess with modern computers like the Vic 20 or Commodore 64. My Sym-1, Kim-1, ET-3400’s and Quest Super ELF’s have been working for the last roughly 45 years and don’t seem to ever fail. Then again, I have made a point of replacing the electrolytic caps in the power supplies.
I am thinking of the January 19, 2038 bug coming up. Hopefully, like the Y2K Bug, it will be fixed. A timing thing in the clock for 32-bit systems.
*Does anyone sell those C64 surge protectors against the C64 killer power supplies?*
nope. The 5v regulator is ONLY for the vic2 and the sid. The LED port uses the native 5v line.
Im always living with that fear, I had bone stock 2 working commodore 64, and every time I flip the switch on until I see the basic prompt, I think, "Will it work this time?". But they are the exact same board revision, so if something went wrong, I can try a few things. Also, I'm building my own power supplies for my computers. I make them as overpowered so they will be never under stress.
yeah, my commodore 64 just poof, died out of nowhere, my Apple IIe though miraculously just works, even reads the floppy disks.
New Sub, Detroit, Michigan, US
Well done Sir! I'm a few years newer than the c64 myself, I grew up with first issue Apple ]['s & later 2c's
My first was an outdated Packard Bell 80286, Hard to find one of those.
Keep it Up!@
I made my own PSU (or you could say assembled). The 5v line is universal (it's meanwell), but the 9v line is not. It's a transformer for 110. It's not pretty. It's just a meanwell box and a 9v transformer hooked up to an extension cord.
EVERY piece of electronics….every man made manufactured article, every piece of technology is a “Ticking Time Bomb”, it is just s matter of how long it “tivks” for before the Second Law Of Thermodynamics ultimately gets it!
Before watching - power switch issue??
it isn't just that the original PSU's aren't reliable, they will 100% fry the system. I saw it happen in the video with the 8 bit guy. He was showing how LCDs worked. It spiked up to like 7v or somehting.
Maybe when the PSU went bad, it took out the VIC and the Basic ROM.
Nice, but weird title. Not all old computers have troublesome PSUs, and of course they don't explode, so they're not bombs.
you should try the char rom. I've seen the char rom cause problems it shouldn't be able to do.
every PSU I've seen the 9v line is high. It's AC anyway. Not a big deal. Mine is 13v. My 5v line is pretty much on the money. It has a pot. I adjusted it to perfect 5v. Anything using the 9v line is being regulated internally anyway.
The thing with the US and EU combi power supplies is, that the transformer (for 9VAC) is 230V or 115V. And I think, in the US, the voltage is higher than 115V. Usually even more than 120V, as far as I know. So the output voltage is higher, too. Also, a transformer is an unregulated power supply. The output voltage will be higher than the nominal 9VAC, when the load is less than the nominal current. The transformers should be 10VA. So the nominal current is 1.11A. If you have a nominal 2A output current, the voltage is higher, than a normal „C64load“, which is like 0.7A, as far as I remember. That means, the voltage regulator will get warmer than usual. They have over temperature shut down and that will cause „trouble“.
What the AC/DC modules for the +5V usually do is the soft start. That means they switch on with a delay after the get mains power. The 9VAC is on immediately. So, what should not be done is switching on the C64 before the PSU. I have tried that many dozens of times without any problem, but who knows…
The next thing with the modern power supplies is the injection of mains voltage into the DC output. They are all isolated by a small transformer in the module, but they have a parasitic capacitance between mains and output. That is not necessarily dangerous, but you might feel something, when you touch the user or cassette port. A slight flickering on the skin.
In my PSUs, I connect a 10nF and a 1MΩ in parallel between GND and PE. That ties the secondary GND to PE. It is even visible in the video output. Especially, if you use video to hdmi converters with a modern (switch mode) power supply.
psu?
caps?
Power switch issue !
Dude youre c64 8s blue what do u expect??
I listened to mine and I did not hear any ticking. j/k
Why only 'retro computers' when each and every piece of technlogy is a time bomb? And I am pretty sure, that the vast majority of hardware released within last 20 years will die even before most of the remaining 80s technology ;)
had the same brand psu for my amiga 1200 it burnt my 5v rail i wont trust this brand again
You 'are getting old..put heatsink on chips, make protect pcb with relay and zener diode.
Good information, but somewhat annoyed that you felt you needed to use a click-bait title for the video.
It's not 'Retro Computers' it's 'Vintage Computers'.
Interesting - but I would say "A Ticking Bomb" is Clickbait and not worthy of your time.
Ordinary titles get buried by the UA-cam algorithm.
As chips in the C64 especially are prone to dying ( think MOS, MT or even the ULA in the Spectrum etc etc), then yes, they are ticking time bombs as they WILL die at some point!
This video could do without the alarmist clickbait title. Most of the video was about a flaky power supply, that is nowhere near the same thing as a flaky / failing computer.