My 12V power supply conversion using PICO PSU and ATX4VC

skate323k137 wrote:

Interesting approach, your work looks very neat/clean.

 

Do you know the mA rating for each rail? Safe to assume they exceed the original? 

 

Cheers,

Alex

Thanks. I wanted the machine to look standard internally, which is why I went down this route. I had originally intended on using the insides of a Flex ATX PSU, but it proved to be too hard to package.

I'm not certain of the amperage outputs of the Streacom Nano 120 PSU, it varies depending on where you look across the web, but I think its safe to assume it exceeds what the Apple ][ requires on all rails.

The ATX4VC can handle 5A on any single rail or a combined total of 7A. 

softwarejanitor wrote:

That's a pretty neat solution.  What does all that cost to put together?  If it is cost effective compared to other options like the ReActive Micro supply board it could be a marketable product.

 

Not including what I spent on things I didn't actually need or use, or the tools I bought, it comes to £48.58 ($61.49) without the Pico ATX PSU.

I paid £40 for the unused open-box Streacom Nano 120 w' power brick, so the cost to me for this one was £88.58 ($112.02)

But a kit would likely require the buyer to supply their own pico PSU, and you can get lower quality ones for $10 from China and re-use a power brick you have laying around, if you so wish... 

With a cheaper PSU it would cost about the same as or a little less than the Reactive Micro solution. The pros being that it doesn't require you to cut your existing cabling or re-use any parts, making it easily reversible with next to no effort, and the cons being that it uses an external power brick.

Me being in the UK and the cost of shipping and taxes is the main reason why I didn't just buy one of those! 

I could probably sell kits (without the PSU) for about £70 inclusive~, but I don't think it would be an appealing purchase.

softwarejanitor wrote:

Akagi wrote:

softwarejanitor wrote:

That's a pretty neat solution.  What does all that cost to put together?  If it is cost effective compared to other options like the ReActive Micro supply board it could be a marketable product.

 

Not including what I spent on things I didn't actually need or use,

I must admit, I didn't do it with the intention of making more. There are a lot of leftover bits of wire and old connectors and things used in this which I'd have to buy in. But I think I could probably get all the parts for less than I paid. For instance the switches and things were say, £3 each, but if I bought from an electrics supplier, they would probably be £3 for 10 or something. 

But then, I would probably struggle to sell 10, it is a very niche market! 

I will ponder it anyway. :) 

skate323k137 wrote:

Posting the instructions alone is a pretty solid contribution, you don't need to monetize it if you don't want to. I just appreciate clean modification work, especially when driven by what a person may have on hand already. 

I was giving it some thought only because I'm scratching for something to do right now, looking for work etc haha.  

I'll just add a few more details...

- [PLEASE MAKE SURE THE POWER SUPPLY IS OFF, DISCONNECTED, AND FULLY DISCHARGED BEFORE WORKING INSIDE, IF YOU ARE UNSURE, LEAVE IT FOR SEVERAL DAYS BEFORE ATTEMPTING]

- To remove the original power supply internals, remove the strain relief bushing by rotating it until the detachable section aligns with the opening in the casing, then pry it up. Undo the 6 screws holding the board in place, and undo the 3 screws at the back holding in the power socket and the ground wire. 

- There are a few different Apple II power supply board designs, on some the power switch / socket wires are connected to the board with push-on connectors, on others they are soldered. The push-on type will have the wires mounted bolt upright and the lower cm or so will not flex. You can pull these directly up and off of the board. I used pliers with tape wrapped around the jaws to achieve this. You will still need to cut or desolder one wire that goes from the power switch to the back of the socket. If your wires are soldered, you will have to either cut or desolder them. If you choose to cut them, I recommend doing it as close to the middle as you can, so it is easier to attach them back together in future. 

- The ATX4VC board is available from DekuNukem on Tindie, and you can find details about the design on Github. Use your Google-fu! Things move around!

- The 2 pin connector I used for the power switch is from a flex ATX power supply fan but you can use any 2 pin connector, like a typical motherboard front panel type connector if you wish. 

- The PCB is mounted on 3mm adhesive stand-offs and is backed with some non conductive black plastic from an old power supply which I cut to shape and punched holes in for the standoffs and for the power wires to pass through. 

- The power switch cannot be a momentary button, you need a latching type switch, or a traditional on/off click switch like you'd find on a regular power supply. That is what I have used here. The dimensions of my power switch aren't quite correct, so I won't quote them here, please measure the hole and don't guess like I did! 

- Some pico ATX power supplies will have a ground wire and loop on the cable, you can mount this to the original earthing point next to the power input socket in the corner. Also please pay attention to which side of the power supply board the headers are on, as this can vary and you might not be able to mount it correctly. 

- The outer "trim" part of the power connector is just cut from a standard C14 panel mount connector, it isn't neccessary, it just makes it look tidier in my opinion. 

- The 12v barrel jack mounting plate is just made from 2mm thick plastic, I used tufnol because its what I had, you can use whatever is on hand. The hole spacing etc is the same as a standard C14 connector. The barrel jack hole may differ depending on your particular power supply, so please check. 

- You can connect a power indicator light to the ATX4VC using the other two pins next to the power connector if you wish, I decided not to do this as it isn't neccessary on these machines. 

- The cables are managed using adhesive wire clips from eBay, they aren't required, but do tidy it up. You could also shorten the Pico PSU 12V input wires if you want, I decided not to do this in case I want to use it for something else in future. 

- I recommend using 18 gauge wire for the main power wires, this is the thickest gauge that will easily fit through the original strain relief bushing. You need about 29cm of wire outside of the power supply for a comfortable route to the motherboard connector.  

- The connector that plugs into the ATX4VC is a 7P VH 3.96 female connector. Please note that you need only use the +12, +5, -12, -5, and a ground. You don't need the +3.3 or the +5sb. You can pick up the additional ground either by inserting two wires into the connector, or by plugging into the ground position on the clamp down block, which is what I opted to do.

- The connector for the motherboard is available new at the time of writing, it is a 1-640520-0 connector. Please note that the schematic on the power supply is viewed from the BACK of the connector as the wires go in. Please bear this in mind when inserting the wires! 

- Check your voltages and then re-check them, and then re-re-check them, before plugging the new power supply into the motherboard. 

- The fuses supplied with the ATX4VC are 5A. You can take an extra precaution by changing the 5V fuse to a 3A and the 12V fuse to a 2A if you wish. From outside to in, they are for 12V, 5V, and 3.3V (unused) 

- The easiest way to keep track of all the nuts, bolts, and washers which were used to mount the original components, is to put them back where they came from!  

- Any questions please ask, but remember that I did not design the ATX4VC, that credit goes to DekuNukem. They did all the hard work. 

CheshireNoir wrote:

Well done. I think if I was going to rebuild mine again, I'd follow your path.

I'll post pictures of my conversion over the weekend with a bit of luck. Mine is built out of a MeanWell medical PSU and a small 7905 circuit to cover the -5v rail.

 

Chesh.

Thanks Chesh

If I had sorted out my soldering situation (i.e bought a decent iron and stuck at it until I learned......) I would have attempted similar to you, making a 7905 circuit and probably using a Flex ATX PSU simply because the PCB fits, and you can get them for $8~ on eBay for a decent quality FSP unit.

In fact I bought one first and tried to use it with the ATX4VC board, but I couldn't package it correctly so I gave up...  

Interested to see yours when you get the chance! 

Um. All of my images are dead, and I can't edit the original post? What happened? Mods? Is there a way my post can be unlocked so I can add them back please? 

My bad. But is there a way to edit it? Otherwise this thread is basically void and I'd have to make another one. 

Because this is now fairly useless to anyone who might find it via googling. :( 

jeff d wrote:

Can you reply to this thread, and add the images? I'd like to see what's now gone.

On it!

OK so uploading pictures to the "proper" way is horriffically tedious... But anyway! 

The ATX4VC and lead made using 18 gauge wire and 1-640520-0 connector.

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Backing made from insulating plastic from an old PSU, and lighter gauge wires passed through to go to the power button.

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The old internals removed.

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  Fitting it all in.

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Trim for the rear of the PSU made using a recycled power connector. 

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All fitted and cable managed.

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The inside before, with the original wiring etc.

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And now.

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How the rear now looks when installed.

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Everything is easily reversible, just screws and adhesive bads. Cheers. :) 

softwarejanitor wrote:

That really looks nice!

 

 

Thanks! The machine is all packed away for now while I work on more modern retro projects (from about 1999 to about 2006) But it was still working properly, firing up first time every time even after sitting for weeks. 

So whatever my issue was before it was definitely related to the power supply.