IBM-5150 Expansion Unit Arrives

The IBM 5161 Expansion Unit. A very rare piece of IBM history. Also the one peripheral that most IBM PC owners can only dream about. There is a long story here, but I’ll try to keep it short.

During my earlier days of vintage computing, over 18 months ago from the date of this writing; I stumbled across a single line in a document somewhere that mentioned the IBM 5161 Expansion Chassis. I believe it was the old, now defunct. Well, that particular line was almost prophetic. As I made new friends, and became more familiar with the Vintage Computer Forums at, I brought up the subject of the expansion unit. Unfortunately, the only information anyone could give me on the expansion came from their own experience, or from knowing someone who had one. There were only two members in the Vintage Computer Forums who had one. But, one day, another member named Ole Juul offered to give me a complete set of extender and receiver cards for one. So I took him up on his offer. I figured that as long as I had these, I could possibly build myself one, using these cards as the core component.

However as fate would have it, about six weeks later another member came onto the scene as a new member. (I don’t remember his name, sorry) He was looking for an extender card for his expansion unit. Well, I was not about to just give mine up, so I offered to purchase his expansion chassis for $125.00. To my surprise, he refused my initial offer and countered with an offer of his own. He would sell me the rest of the expansion unit for only $40.00, but he needed to keep the hard disk drives.

We had a deal.

When the chassis arrived, it was stuffed with paper, bubble wrap, artist paper, and even some newspaper! Wrapped up inside the case was a hard disk controller for dual MFM drives, and he had installed a 30 Meg full height hard disk. But it was the wrong disk for this computer and expansion unit. Since the controller had a broken plastic corner, and it had the aforementioned incorrect hard disk, both were removed and a search began.

Through the VCF, I was able to locate a new Western Digital MFM controller and TWO internal MFM hard disk drives.

This particular set of pictures show what was included with the expansion unit, when it arrived, and the chassis overall condition. With the exception of a single scratch along the top of the case, there really isn’t anything remarkable to report. Just like the PC, the unit looks to be well cared for, all of the painted surfaces are clean and no signs of rust. There was a bit of dust and dirt inside, but nothing extraordinary. About the only real caveat was the hard disk drives missing front panel, and the missing cork feet on the bottom of the expansion unit’s case. Luckily, I know someone who has a supplier of these cork feet, and they look, and feel just like the original. A quick phone call, and the now cork pads were on the way, as were two replacement hard drives, and a few other internal parts.

Assembly was pretty simple as we’ll see in upcoming photos.

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