
C64 / VIC20 / C128 PSU Open Sourced - ingve
http://www.retro-commodore.eu/2019/01/15/c64-vic20-c128-psu-open-sourced/
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randrews
For those wondering why this exists: the original C64 PSU has a (common)
failure mode after a few decades, where it will output power in such a way
that will destroy the C64 (and its irreplaceable MOS ICs). If you find an old
Commodore and you want to test it, don't plug it into the original PSU without
testing that first with a multimeter!

~~~
Jaruzel
The VIC20/C64/128 PSUs have standard 5V DC AND also have 9V _AC_ pins to power
the SID chip (among others). Which means it's not that easy to just pick up a
standard transformer and wire the right connector onto it.

A lot of the new Commodore and Amiga Hardware being developed these days is
open source, which is 100% a great thing, enabling us to keep these classic
machines running for many years yet.

~~~
moftz
It seems like it would be pretty easy to just have a step down transformer
from 120VAC to 9VAC. Also wire up the 9VAC to a bridge rectifier to get 9VDC
to then convert down to 5VDC with an LDO or buck regulator of proper current
rating. It wouldn't be the cleanest power supply but the C64 board should have
proper filtering for each rail.

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zokier
Nice job finding a good source of parts for this. I might as actually build
something like this.

There are few things in the PCB design that I might want to change. The live
and neutral are precariously close to each other near where live connects to
transformer. Also the mounting screw is very close to mains voltage. Maybe I'm
just paranoid about mains voltage, but I'd increase the clearances,
considering that there is plenty of board space. While we are changing the
board, I'd also bump the trace widths on the low-voltage side, although I
don't believe that being really a problem now.

Then comes the parts I know less of. Would it make sense to add some filtering
to clean the power? I'd imagine it works perfectly fine without, but maybe to
improve audio/video quality? Also the fuse is on the "neutral" side, is that
good? Although the plugs around here are unpolarized anyways, so the
distinction can't be very significant.

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rzzzt
The output is produced by a Meanwell power supply, it's like a wall wart with
through-hole legs: [https://www.meanwell-web.com/en-gb/ac-dc-single-output-
encap...](https://www.meanwell-web.com/en-gb/ac-dc-single-output-encapsulated-
power-supply-irm--10--5)

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gizmonty
I can remember my C64 being out of action for weeks at a time (months even?)
due to the power supply failing and having to wait for - I don't know what;
repairs? parts? It happened more than once. This was in New Zealand in the
80s. It was a much more isolated place than it is now (and it's still pretty
isolated!) so very slow to get things like this sorted (and service culture
then was very poor - only slightly better now). All dealt with as warranty
issues if I remember correctly, but the time it took was agonising for a
socially awkward 13-year-old!

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SwellJoe
The power supply is one of the trickier aspects of getting a working C64 rig,
and it's not uncommon to spend as much on it, as on the C64 itself. You'll see
a lot of "no power supply, untested" C64s on eBay because of it...in my
experience those are all just actually dead (and maybe known to be dead by the
seller, but the well-known problem with power supply availability gives them
plausible deniability...but, maybe they also tried with a PS that kills the
computer, which also happens sometimes with the original power supplies).

In short, necessity is the mother of invention and what not. The Commodore
power supply was a unique beast, so there are no off-the-shelf replacements,
so there's been an aftermarket for them for a long time and schematics of the
old power supplies have also been available for ages, though having one that
doesn't have a dangerous failure mode is an improvement.

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th0ma5
I bought one of the bare bones power supplies from here:
[http://personalpages.tds.net/~rcarlsen/custom%20ps.html](http://personalpages.tds.net/~rcarlsen/custom%20ps.html)
it is indeed bare bones and two wall warts, but it is very nice. His site
contains all relevant technical info and then some.

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kazinator
Open sourced ... with schematics files for a proprietary CAD program.

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setquk
Removed comment - does have OVP

~~~
woodrowbarlow
hmmm, that's troubling. since you seem to know what you're talking about and
what would be needed to fix it, can you open an issue on the github project?
i'd like to see whether the designers have a response.

[https://github.com/Retro-Commodore/C64-PSU](https://github.com/Retro-
Commodore/C64-PSU)

~~~
setquk
I have removed my comment as that particular Meanwell unit DOES have OVP
included. No issue necessary!

I shall crawl back into my power supply paranoia hole now :)

