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mAcTX - ATX to Classic Macs

blusnowkitty

Well-known member
Hey all, just wanted to gauge community interest to see if anyone would be interested in an ATX to Mac 10-pin adapter board. I've got a IIsi with a dead power supply (surface mount caps got REALLY bad inside) and @Compgeke and I have been working on an adapter board that'll take any ATX power supply and turn it into a 10-pin Mac supply for the compact II series, Quadra 650/700/800, Performa 600 and Powermac 7100 with full support for soft power.

Right now I've got a batch of prototype boards being made to test out in my IIsi. Once we get that up and running, I'll start offering boards for sale if anyone's interested. Probably going to be sold as PCB only, kit, and fully assembled options.

Will keep you up to date - if this works out, we may also work on an ATX adapter board for the II, IIx and IIfx that'll also solve the pesky startup battery issue those things have!

 
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JDW

Well-known member
You're talking about a simple "cable/connector" adapter with one side plugging into the big connector on an ATX PSU and the other connector plugging into a Mac (including SE/30)?

 

mattsoft

Well-known member
It might be possible to design an all-internal solution using a Pico-PSU and simple AC-DC open frame PSU. I did one these a year or so ago for the Sharp X68000 and it works great and looks stock. Someone could easily adapt it for a Mac.

 

Compgeke

Well-known member
Nope, it's an actual PCB with an inverter for the /pfw line included on the board. A bit prettier than cable splicing and soft power will still be retained, rather than being hard on or off. You can buy the Molex connectors Apple used in a solderable package meaning assembly isn't too difficult. Even included a fan header so you can retain the cooling system needed, however how to mount that is a later problem (3D printed bracket or something that slides into the original mounting spot I guess). 

Combine with a PicoATX PSU and it'd be a reasonably pretty internal setup, providing you aren't running a bunch of nubus cards or a pile of big hard drives. The original PSU was designed for 5V 12A whereas your average picoatx will be closer to 8A. The only real "catch" is the -12V line is pathetic on most ATX PSUs, pico included, but to the best of my knowledge it's not used by much of anything except some nubus cards. It's only 1A on the factory PSUs anyway. 

I don't have a screenshot of the test board that's being produced right now, but here's an earlier screenshot. With any luck it'll fit the IIsi but some rearranging may be required with regards to overhang on the end. Some sort of support will also need to be figured out but that's easier once we have an assembled board with the connector to know what clearance is going to be under it, 

NotFucked.png

 

Byrd

Well-known member
Yes, I'd be interested in a few bare DIY boards, if anything to have a known good PSU for testing Macs.  You'd also have a good market for SE/30 boards if you decided to design.

 
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blusnowkitty

Well-known member
While I wait for the boards to ship, I went and hooked up my IIsi straight to an ATX power supply. Turns out the IIsi doesn't really like it if you don't connect +5VSB; thankfully there doesn't seem to be any damage. 

IMG_3959.JPG

IMG_3961.JPG

 

Compgeke

Well-known member
You'd also have a good market for SE/30 boards if you decided to design.
So this one isn't quite as straight forward as the Mac II stuff is. It's mainly down to the requirement for the -12V rail and cabling to go from whatever is designed to the analog board.

The first idea is to do something similar to the Artmix design and use an industrial PSU with custom cabling off that. This would be my preferred option really since it cuts $30-$40 off buying a Flex ATX PSU. The specs on the unit I'm looking at are 5V 12A, 12V 5A, -12V 1A. That would effectively double the output capacity of an original Sony Mac SE PSU while only being $35 for a PSU. I'd still need to crimp some stuff together for the actual harness and a fan connection, but it'd undercut the Artmix design by a lot. We're talking ~$60 in parts, however it would not be fansay inside a Mac SE PSU box. That'd be on you to supply. 

The other to do this would be to base it on a Seasonic or FSP Flex ATX PSU with a custom harness built. All three of those companies make power supplies with a male header on the power supply rather than built in cables.
image.pngimage.png

More or less the easiest way to do it would be invest in some minifit connectors and just remake a new harness, something that goes from the PSU's proprietary connector to the 10 pin Molex of the Mac SE power supply connection. I don't think there'd be much of an issue with needing to isolate a 12V rail for the sweep circuit, however if there is it isn't hard to hack a small inline PCB in that would just apply some extra filtering to the lines going to the sweep connection. Using these you don't have to worry about dealing with excess cable like you would with an adapter that plugs into a normal ATX end. 

 

BadGoldEagle

Well-known member
The main issue with modern PSUs is that they can't really output more than 20A on the 5V rail. The old 800 PSU could do 30A, and the Delta unit in the 9x0s could do 33A. I know they probably don't need all that power at all times except perhaps if you intend to use them as an old school server with more than 10 hard drives in them... but it's kinda difficult to know what the actual current draw is. I'd say it would be about 18A maximum to power the board and drives but I wouldn't feel very safe with a saturating cheap aliexpress PSU in my machine...

For the Mac IIs or the Q650/700, modern ATX PSUs are still within the limits.

 
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Trash80toHP_Mini

NIGHT STALKER
From what I can see the plug shapes seem right, it would be interesting if the wiring matches too.
Buying the extraction tool for the contacts in the connector and swapping the wiring around to match would be the way to go from what I've seen  in the last couple of years. Surprised I hadn't seen that method before.

The main issue with modern PSUs is that they can't really output more than 20A on the 5V rail.
Aux 5V PSU should work, no? I've got a 300w FlexATX PSU slated for a IIsi can. A pair of them could be fitted into the IIcx form factor can as the absolutely worst case scenario, so adding an aux 5V power supply could be easily done?

 

BadGoldEagle

Well-known member
I've noticed that heavy duty aux. PSUs are rather heavy. I had found a 35A 5V industrial PSU but it weighted about two pounds...

What kind of amperages can your FlexATX deliver? For a IIsi, power isn't a problem. 

 

jessenator

Well-known member
I came across an analogous PSU replacement issue on Vogons and it lead me to this PSU—not sure if this is max or peak load, but 50A on +5 V, not too bad:

https://www.ebay.com/itm/292609545791

Doesn't look ancient at any rate. So there are solutions, just extra digging required.

Other SATA power to molex adapters might be in order, but still. Newegg (seller) link: https://www.newegg.com/p/1HU-01AD-001F4

 
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jessenator

Well-known member
well in my haste, I failed to take reviews into account. It's pretty bad… It's roughly 60/30 split between 1-star and 5-star respectively, with most complaints being failures. oh well, back to the search.

 

Trash80toHP_Mini

NIGHT STALKER
Dimensions are almost spot-on for inverting that Newegg PSU to replace the IIcx can.

Newegg-PSU-detail.JPG

Bending a sheet metal wrap for that can on a box & pan brake would be easily done. Pop riveting or screwing it to side and back would yield mounting flanges, angle at back and all. Might need to do some surgery on the back side of the can to clear the snap? Dunno looks pretty good to the digiper readings for that. Dunno, worth a try anyway, the 3D model in my noggin looks pretty good.

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Trash80toHP_Mini

NIGHT STALKER
well in my haste, I failed to take reviews into account. It's pretty bad… It's roughly 60/30 split between 1-star and 5-star respectively, with most complaints being failures. oh well, back to the search.
Is that for eBay or Newegg? Can't imagine a Mac testing a 680W PSU to the point of borkage.

 

jessenator

Well-known member
Is that for eBay or Newegg? Can't imagine a Mac testing a 680W PSU to the point of borkage.
Amazon (sorry should've posted link) Yeah, my PowerWave's SeaSonic was rated to 200W if that says anything. I doubt even a fully loaded Q950 would pull that, but that's not my wheelhouse.

https://www.amazon.com/KENTEK-Supply-EPS12V-ATX12V-PCI-Express/dp/B006XJYVZW#customerReviews

Yeah, who knows what systems they were building (saw one mATX), but if they were smart they wouldn't push it too far, so I'm guessing most systems would be 70–80% of the max load, so 500–550W system draws. That's my philosophy anyway—I don't want my max potential load anywhere near the max of the PSU. I think my Ryzen 2 rig pulls <600 W on my 750 W supply. But they aren't me I guess.

Edit, I'm only pulling ~500W stock :lol: maybe my PSU was overkill.

 
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