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The IBM PCjr was marketed by IBM beginning in 1984 and was intended to be a low-cost alternative to the IBM PC. Primarily intended to compete with other popular home computers like the Commodore 64 and Apple II, it was equipped with an Intel 8088 and the base model came with 64KB of RAM for $669. Notable for the time, the PCjr had a wireless infrared keyboard and “sidecar” expansion modules which allowed for various upgrades to the machine’s capabilities.
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As a millennial born in the late 1980’s, I completely missed the 8-bit computing era. Machines like the Commodore 64 and IBM PC were before my time and well before the time I was old enough to start showing interest in computers. However, when a friend of mine in Texas won an IBM PCjr in a local auction from the Reusum Collection in Boise, Idaho, I couldn’t help but be excited that this unique and interesting machine would be spending some time in my computer lab until he would be able to pick it up in person. The PCjr was his first childhood computer and I’ve enjoyed learning about the era of computing that I missed through the Commodore 64. All this is to say that I’m extremely appreciative to have the opportunity to explore an 8-bit PC compatible and to share the excitement with a good friend of mine. It wasn’t long until our conversations were dominated by plans for the PCjr and discussions about what parts we needed to get it running.
Having never seen a PCjr before, I didn’t know that this PCjr was larger than it should have been on my first inspection or that would have been the first thing that stood out. It seemed to me a relatively generic beige box with dual 5.25” diskette drives and plastic that was in excellent condition. However, as my hands quickly showed after the first handling, it was very dirty and in need of a good cleaning. Clearly this PCjr had been sitting on a shelf somewhere for quite a while and accumulated a good layer of dust and grime.
Dual 5.25” diskette drives and a missing PCjr emblem from the front view.
The right side of the machine looking at the sidecars.
The rear of the machine - at this point I did not realize I was looking at a Racore expansion.
The left side of the machine.
At this point my friend had informed me that this particular PCjr had a Racore expansion installed so we decided the machine needed to be opened up to see what upgrades it may have. Opening up the case and poking around showed that it had a memory expansion in the Racore as well as an additional IBM PCjr 128KB memory expansion sidecar. I also found something entirely unexpected: a corn flake.
We also realized that we were also missing not one, but two, external power bricks. One to power the PCjr itself and one to power the Racore Companion Drive Two Plus expansion. Planning to find replacement power bricks or replace the power boards themselves with more modern alternatives began at once.
The corn flake made me realize that the time had come to start cleaning up the PCjr. I wiped down the outside and accessible interior surfaces of the main body of the machine and sidecars with mild alcohol wipes at this point. I also removed the corn flake.
A view inside the Racore expansion: memory expansion (top-right), power board (bottom-right), and 5.25” drive (left).
A view inside the Racore sidecar with a nice view of an early AMD IC. AMD was already by this time producing an Intel 8088 clone under license agreement with Intel and selling them with extremely high profit margins to military customers.
An original IBM PCjr 128KB memory expansion sidecar.
Inside the IBM PCjr 128KB memory expansion sidecar.
The cause of the rattling sound I heard inside of the memory expansion sidecar.
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This section contains documentation and external projects we found useful during the restoration process.
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GitHub - AkBKukU/ATX2PCjr: An ATX adapter for power an IBM PCjr
Racore Companions™ Drive Two Plus (Model 1500/1501) Installation Instructions