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Pico ATX PSU kit for Macintosh SE, SE/30, 128K, and Plus

dekuNukem

Member
Hi there! I designed a few PSU replacement kits using modern PicoPSU ATX power supplies.

Currently for Mac SE, SE/30, 128K/Plus, and Apple II line.
  • Open-source
  • Non-destructive and reversible.
  • Low cost, easy assembly, clean looks.
  • Standard PC fan header
  • Fused outputs
Details and instructions here: https://github.com/dekuNukem/PicoRC/blob/master/README.md

It replaces/bypasses the old PSU all together, which I find more stable and reliable than recapping and replacing old components.

Happy to answer any questions!

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MrFahrenheit

Well-known member
Hi there! I designed a few PSU replacement kits using modern PicoPSU ATX power supplies.

Currently for Mac SE, SE/30, 128K/Plus, and Apple II line.
  • Open-source
  • Non-destructive and reversible.
  • Low cost, easy assembly, clean looks.
  • Standard PC fan header
  • Fused outputs
Details and instructions here: https://github.com/dekuNukem/PicoRC/blob/master/README.md

It replaces/bypasses the old PSU all together, which I find more stable and reliable than recapping and replacing old components.

Happy to answer any questions!

three.jpeg


title.jpeg

This is amazing!! Thanks for doing this, and sharing with the community!
 

joshc

Well-known member
Looks nice and tidy, definitely a good solution for those who aren't comfortable doing an ATX PSU conversion within an original PSU enclosure.

Any plans to do a version for 600/650/IIcx/IIvx/IIvi/IIci/7100 machines (those all share the same formfactor PSU).

Also a version for LC I/II/III/475 would be nice to see.
 

Phipli

Well-known member
What DC power supply are you using? The SE and SE/30 PSU is rated at 100W, you'd need a fairly substantial 12V brick.
 

CC_333

Well-known member
What DC power supply are you using? The SE and SE/30 PSU is rated at 100W, you'd need a fairly substantial 12V brick.
Yes, and also, what's driving the CRT? Or is this designed to pair with an LCD conversion?

c
 

Phipli

Well-known member
Any plans to do a version for 600/650/IIcx/IIvx/IIvi/IIci/7100 machines (those all share the same formfactor PSU).
Despite what the ebay sellers say about their power capabilities, you'd struggle to use one of these in a IIci. You'd need an external PSU almost as big as a stock IIci PSU. Once you get above 100W you're looking at PC PSUs or industrial PSUs to power thd barrel jack.
 
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dekuNukem

Member
What DC power supply are you using? The SE and SE/30 PSU is rated at 100W, you'd need a fairly substantial 12V brick.

Just a regular 12V DC power brick, mine says 40W and runs the stock Mac SE/30 and Mac Plus just fine.

Of course you can buy higher powered bricks, they are very common so very inexpensive as well.
 

dekuNukem

Member
Yes, and also, what's driving the CRT? Or is this designed to pair with an LCD conversion?

c
This is designed for completely stock machines with CRTs.

The CRT in early Macs actually runs on 12V, that's why this simple adaptor can provide all the voltage it needs.
 

joshc

Well-known member
A 40-50W PSU would power an SE or SE/30 fine, but not if the machine has upgrades like PDS cards I assume.
 

Phipli

Well-known member
Just a regular 12V DC power brick, mine says 40W and runs the stock Mac SE/30 and Mac Plus just fine.

Of course you can buy higher powered bricks, they are very common so very inexpensive as well.
Yikes, that's less than half the power rating on the input to the pico.

I worry about these things. Barrel jacks are usually rated to 5A or less, sometimes 7.5A and legend says, there have been 10A ones. The power figures being thrown about for these things, you'd struggle to push it in through a barrel jack, even if you found a PSU that had enough grunt to provide 8A or more at 12V :s

I need to dig out how the Pico is rated for the different rails too, Macs tend to lean heavily on the 5V rail, unlike modern PCs.

Excellent for an LC though :)
 

Chopsticks

Well-known member
nice design there, fwiw with a 12v 40W psi that's only about 3.3A, so it's going to be important to check exactly what the se/30 requires on each rail. I don't have a se/30 open in front of me right now but from memory the +5v rail is speed for around 6A and the two 12v rails combined are around 3.35A.
there's also the -12v rail that some Pico PSU's don't provide

so two things of note here.

firstly the se/30 psu is spec'd to be able to power an internal PDS slot card along with those old power hungry SCSI HD's, so depending on if you had a PDS card and also say if you have a modern HDD replacement you might get away with a lower output on the 5v rail

secondly you 12v input rail isn't really enough, at 3.3A input to the Pico PSU there's just not enough juice for both the 12 and 5 rails, so depending on the conversion efficiency of the 12->5v conversion on the pico don't be surprised if you actually need something like a 12v 80W DC brick or possibly ever higher like 100w.

its important to note that just because something it rated at 40w doesn't always mean it runs well or last longs at that rating. good rule of thumb is to allow 30% headroom when feasible
 

Phipli

Well-known member
I don't have a se/30 open in front of me right now but from memory the +5v rail is speed for around 6A and the two 12v rails combined are around 3.35A.
there's also the -12v rail that some Pico PSU's don't provide
I found this (here):
Screenshot_20230126_213918_Firefox.jpg
And this :
Screenshot_20230126_213201_Firefox.jpg

Looks like the -12 is rated at 1/10th, but the 5V is up to spec. You'd need a huge DC psu.

Off those numbers, assuming the pico is 90% efficient, you'd need about 85W DC supply, aka 7A 12V (to match ratings).

There are supplies that meet and exceed this available, so it's an excellent way of swapping out the PSU without worrying about the space envelope. I am a little worried about so much current through a small barrel jack though. A 24V version might be good? It would half the needed current and should be just a straight swap for the 12v version?
 
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Chopsticks

Well-known member
so further info in case its helpful, I just went and checked the specs out the picoATX-80 it'll and it it'll provide enough amps on the required rails but even they use a 60w 12v DC with the 80w pico. however I stand by what I said in my last post about needing at least a 80w 12v dc brick (100w recommended).

I'd highly recommend you update you GitHub and Tindie store page to mention something about the 12v DC brick requirements, might save you some hassles with customers/support emails etc in the future.
 

dekuNukem

Member
Very helpful insights! My 40W brick and 80W PicoPSU seem to work with the bare SE/30 itself, but things might change if you add upgrade cards, external floppies, and other peripherals. A beefy PicoPSU and 12V brick surely wouldn't hurt! I'll update the documentations.
 

Phipli

Well-known member
Very helpful insights! My 40W brick and 80W PicoPSU seem to work with the bare SE/30 itself, but things might change if you add upgrade cards, external floppies, and other peripherals. A beefy PicoPSU and 12V brick surely wouldn't hurt! I'll update the documentations.
I just spotted your fuses are 5A too - the stock powersupply is rated to 6A on that rail so it might be worth bumping it to 8 or even 10A? It would avoid having customers with tricked out machines and a big enough power brick, blowing the fuse in "normal" use.

I say this because my 40MHz SE with two hard disks... well, the neighbourhood lights dim when I play Prince of Persia :)
 

Chopsticks

Well-known member
Off those numbers, assuming the pico is 90% efficient, you'd need about 85W DC supply, aka 7A 12V (to match ratings).

There are supplies that meet and exceed this available, so it's an excellent way of swapping out the PSU without worrying about the space envelope. I am a little worried about so much current through a small barrel jack though. A 24V version might be good? It would half the needed current and should be just a straight swap for the 12v version?
I believe the pico varies between around 85-96% efficiency depending on the rail and there amps drawn.

also im pretty sure they use a 5.5mm or larger or the centre pin dc jack should handle somewhere between 5-10amps from memory (standard/typical dc jacks are 2.1mm)

Very helpful insights! My 40W brick and 80W PicoPSU seem to work with the bare SE/30 itself, but things might change if you add upgrade cards, external floppies, and other peripherals. A beefy PicoPSU and 12V brick surely wouldn't hurt! I'll update the documentations.
when selling a replacement electronics product its best practice to ALWAYS make sure it at minimum matches or exceeds to specs of the original part. so even if you don't have a fully decked out SE/30 you should assume every single customer does and make sure you product can meets those requirements. also assume the lowest common denominator in terms of a customers knowledge/understanding/background when it comes to the Instructions and required parts needs.
the ultimate goal there is to reduce as much the potential need of repeating customer service to explain/help when a product you sell doesn't work for that person due to them not understanding something in the documentation properly.
I just spotted your fuses are 5A too - the stock powersupply is rated to 6A on that rail so it might be worth bumping it to 8 or even 10A? It would avoid having customers with tricked out machines and a big enough power brick, blowing the fuse in "normal" use.

I say this because my 40MHz SE with two hard disks... well, the neighbourhood lights dim when I play Prince of Persia :)
8A fuse on 5v rail and 4A on 12v rail, I wouldn't go as high as 10a. I can't see an initial surge in inrush current on power on drawing that much. fuses can get complicated though because you also have trip current ratings to deal with too...
 

Phipli

Well-known member
standard/typical dc jacks are 2.1mm)
I thought 2.1mm was the pin size, rather than the barrel isn't it? 5.5/2.1 describes a 'normal' barrel jack, outer and pin diameters respectively.

Edit - re reading your post I think that is what you meant.
 

Phipli

Well-known member
@dekuNukem

Nice github avatar BTW :) there is some overlap between here and stardot. I have an A3010, Electron, some Bs and a very dead Master. You also seem to be fairly local to me.
 

BGMK

New member
I was planning to figure out how to convert my Mac Plus from 230v to 110v but this seems to be a better plan..... has anyone done this mod on their Plus yet?
 
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