I’ve been working on a modern internal power adapter project for the IBM PCjr that I’m calling VoltBus.

The goal was to create a cleaner replacement for the aging stock power setup while keeping the machine looking and feeling as original as possible from the outside. I even sourced most connectors and switch from the old power board.

The original inspiration for using a PicoPSU style setup came from an old forum post I ran across years ago. Unfortunately I can’t remember which forum or who originally posted it, but the concept stuck with me and eventually turned into this board.

Current Rev A prototype features:

- PicoPSU support
- support for a rear-mounted power switch
- internal installation
- LP4 disk power connector
- matte black PCB with white silkscreen

One thing I discovered during testing is that some PicoPSU clone boards do not correctly handle startup from the loose external green trigger wire. The fallback that worked reliably was using standard ATX pin 16 PS_ON directly through the switch to ground. I’ve documented both configurations for builders.

The goal with VoltBus is not to heavily modernize the PCjr, but to make something that feels like a clean late-era hardware revision that still respects the original system.
I already have a list of revisions for Rev B including a windows for pico cables to pass through to allow a 90 degree connector and the pico to lay flat, more compact. Internal PC_ON trace to switch, and a few more.

I may eventually design separate stackable add-on boards for power distribution or cooling, but this Rev A board is only the PicoPSU power adapter itself.

Still refining the design, but I finally have a working prototype installed and running inside my system. I still need to make a bracket to hold the DC barrel jack to complete the almost stock look. Interested to hear thoughts from other PCjr owners or anyone who has experimented with modern internal power solutions on vintage hardware.

A few photos of the current Rev A prototype are attached below.