Mike's PCjr Page

Hello,

I recently have designed an adpater for the PCjr that let's you use an ATX power supply on it rather than the 18VAC external that it *should* come with. My PCjr was found without the AC PSU after after seeing the scarcity and price of them on ebay I figured there had to be better way, so I made one.



As an aside, I was waiting on posting about this on forums until I got my second batch in. I knew I was going to sell out of the first 9 I had really quickly and didn't want to tease people here that I made something but that you can't get it. Maybe that wasn't the best choice, I'll try to post more progressively about stuff like this in the future. As of this post I have most of the parts in for the next batch of 29, I'm just waiting on PCBs and some female headers.

I also figured I should make my own thread for is so I can update the original post when things change. If it is preferred that I post in the other thread then this one can be deleted.

When they come back in stock I'll be selling them here: https://akbkuku.com/store/p/1/IBM-PCjr- ... y-Adapter/

Kits are $15 and I'll assemble it for $5.

The design files are open source and available on Github: https://github.com/AkBKukU/ATX2PCjr

It has the following features:
Compatible with a standard ATX PSU for easy install
Compatible with PicoPSU for compact and seemless installs
ATX PS_ON connected switch for power on/off
Two 3D printed rear panels for ATX or PicoPSU use
Floppy and fan power connectors

I welcome any feedback or questions about the design. I've tried to work on make it as work with the majority of use cases but there could always be something I didn't think of. I do have a question for those who are intereseted, how would you feel about a different power switch? The ones I've sourced that resemble the original as much as possible aren't cheap at $3.38, but I figured most people would rather have something close to the original than save a few bucks.

I saw your video on this and really like the idea of using the PicoPSU. I'll be keeping it in the back of my mind in case I start having any trouble with my official power supply down the road. This definitely would have been a useful discovery if it had been around back when I first got my PCjr, as it was missing the power brick back then, but I've managed to acquire two of the official power bricks by now, so I'm pretty much set...

Brilliant idea! I am getting one from you just to have a spare way to power up my PCjr if the brick dies on me.

I've got these back in stock now and made a new update video on some minor changes: https://www.youtube.com/watch?v=bMzfTIqHQd0

Just ordered one of these from you. Wish I had come across it before sourcing a power supply on eBay a few months back.

I finally got around to assembling one of my kits and testing it out. Here is the finished product:



It works. No magic smoke escaped. And on my system I use an ATX power supply anyway for an external hard drive, so now I'm down to just one power supply that powers both the PCjr and the hard drive.

I have three critiques:

• The power switch screw holes do not line up well on my case. I ensured the bracket was down as far as it would go. Even so, the screw head is interfering with the case. I don't want to modify the case so right now it's a bit loose.
• My ATX power supply did not have a long enough 20 pin cable, so it's close to the back of the machine and it's causing cable routing problems. I ordered a 20 pin extension cable that should help things out.
• The two pins from the motherboard to the original power supply card are left free with this new setup. Is this going to be a problem? (I need to check the tech ref to see what they do.)

-Mike

Brutman wrote:

• The two pins from the motherboard to the original power supply card are left free with this new setup. Is this going to be a problem? (I need to check the tech ref to see what they do.)

They are just mechanical anchors. Nothing electrically conductive.

I installed my ATX adapter with a picoPSU and it works great. The only problem I had was the holes on the 3D printer rear panel for the power input and switch screw were a bit too small, so I had to drill. With the cover on the PCjr, everything is nice and tight.

Could anyone post a link for the exact model of ATX/PicoPSU supply that works with this adapter and the PCjr?

Actually, to modify that question:

I see in AkBKukU's external video on his adapter, he cautions that these power supplies may not sufficiently power sidecars, depending on how many you have.

Right now I have a 128K PCjr with single floppy drive, one parallel sidecar for a backpack 3.5" drive, and a jrIDE board with a KingSpec 8GB DOM. I'm looking at adding a second parallel sidecar to support a Xircom network adapter. So far, everything seems to be working ok with the original PCjr power supply. Would there be a benefit to using an ATX or PicoPSU supply? If so, any suggestions on which one to go with?