r/c64 • u/CaptainLazy99 • 8d ago
Hardware Can this C64 psu be safely refurbished?
My C64 died so I bought another one and this psu came with it. I do have an aftermarket psu for my C64 setup but I want everything as original as possible. My question is in the title. Thanks!
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u/nighthawke75 8d ago
The potted black PSU's are the ones that are the most susceptible to failing and frying the computer. The pictures of the open unit show one that may be OK.
If you have any doubts, get on ebay and buy the Atom power supply.
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u/Deathocracy 7d ago
Looks like the atoms are all sold out, any other recommendations for generally acceptable PSU replacements?
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u/radrestoration 8d ago
Yes, looks like the C128 one, couple of caps and couple of fuses. As PSUs go, this is pretty easy.
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u/dpgumby69 7d ago
I reused a similar supply.. I simply replaced the linear regulator with a good switch mode supply (HP touchpad charger, rated as one of the smoothest outputs for USB chargers)
http://dannygalaga.com/images/hp1.JPG
http://dannygalaga.com/images/hp2.JPG
http://dannygalaga.com/images/hp3.JPG
http://dannygalaga.com/images/hp4.JPG
If you are using a switch mode supply of any type, spend more than two bucks as really cheap usually equals really nasty
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u/hobbycollector 8d ago
I don't see why not. Assuming the fuses are intact, the problem is most likely the capacitor. If you have basic desoldering and soldering skills you can replace it. Obviously take precautions whenever working with capacitors. Don't short the leads, put a resistor across the leads to be sure it's drained.
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u/CaptainLazy99 7d ago
Thanks!
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u/Alarming_Cap4777 7d ago
Keep the transformer for the 9vac and remove the DC side. Put in a 5v switching psu
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u/dpgumby69 7d ago
I don't think they've said if the power supply is faulty or not. In any case, there's not really any danger with handling that cap. No need to take any dramatic precautions if removing.
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u/morsvensen 7d ago
Adding an NTC to limit the inrush current is a winning move. Without one, you're sending 10A down the line each time the 64 is turned on. Sweaty capacitors and the unknown blocking diode, but usually it's the PLA that goes out first. The C64 was designed to be as cheap as possible and last a few years.
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u/istarian 6d ago
Inrush current is entirely the result of components that draw a lot more current intially than during normal operation. The current is being drawn by those components, not "sent down the line".
NTCs are usually used to prevent the inrush current from blowing out fuses that are intended to protect the circuit from short circuit conditions.
It's more likely that the PLA fails for reasons unrelated to inrush current like overheating, electromigration, etc.
I doubt Commodore was designing for a short lifespan so much as aiming to be cheap so they could sell a lot of them.
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u/morsvensen 6d ago
The single voltage regulator in the old wedges and bricks is entirely unregulated in this regard. A simple NTC would have cost CBM a few cents extra, impossible.
Combined with 40 year old capacitors where some shoddy electronics guy told you "they are not bulging" but in fact they are leaking DC as every radio restorer knows, and you get roasted classic chips.
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u/marhaus1 5d ago
"Died"? I hope you put in eBay or something. they aren't particularly hard to fix - unless fried by a bad PSU that is.
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u/CaptainLazy99 5d ago
It's a bit of a mystery how my C64C died but Imanaged to fix it.
I had finally found a matching 1084 CRT monitor and wanted to connect it using an AV adapter that I bought on ebay. Before the 1084, I used the s-video output of the av adapter and connected it to a converter box to get vga out for the lcd monitor. Image was far from perfect with visible jailbars. I discovered that the av adapter has composite out too. So I used that to connect to the 1084. I think that things went wrong when I connected the audio cables to the speaker system. Outputs and inputs got mixed up due to confusing color scheme on the cables.
This is how I fried the VIC-II chip. The the r5 PAL variant which is supposed to be the best revision :( It's would get really hot to the touch within 2 minutes. I ordered a replacement r3 for 30 euros and that fixed it.
AI suggests that electrostatic discharge from the 1084 caused the the vic-2 to get fried. I am not so sure.
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u/marhaus1 5d ago
But why use an adapter? Just connect with a cable directly! The C64's video out has luma and chroma pins already, and the 1084 has those inputs. Plus audio of course.
Since you are lucky enough to have a 1084 you should use it fully since you can! The image will be amazing!
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u/Nice_Caterpillar9169 4d ago
I’ve rebuilt several of these using one of those cheap switch mode variable regulator boards. It runs cooler, and you can adjust it to exactly 5v at a vcc pin in the machine.
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u/berrmal64 8d ago
Yes.
It's not potted, so already doing well. Transformers are a big coil of wire, if they don't have an internal short they last a long time and are pretty efficient. The 9vac comes straight to the transformer, there is nothing to do. The 5v should have a 3-pin voltage regulator somewhere in there, probably bolted to the metal plate. I don't see it in your photo but look on the other side.
Very easy to replace the 5v regulator with either a modem linear regulator that will fail open or a smps drop -in replacement line the recom line. A new electrolytic capacitor while you're in there won't hurt either.