I picked up an IBM 5150 from e-waste while I was looking for a spare part for another early IBM machine. The main issue right away was that the hard drive had already been destroyed, so there was nothing to test there, but the rest of the system looked unusually clean inside. The case had been put back on wrong, and the machine had a pair of half-height floppy drives instead of the full-height setup you usually expect to see in one of these.
Once I got the cover off, I found a nice set of expansion cards. There was an IBM MFM hard drive controller, a standard IBM floppy controller, a Parity Incorporated 512K RAM card with six banks populated, and an IBM async card. The standout card was a Paradise Multi-Display adapter, a two-board assembly in a single slot with a 25-pin connector on the bracket and two 9-pin outputs on the back.
I did a quick check for shorts before powering it up. At first I thought I saw a short on one of the negative rails, but when I checked again I wasn’t seeing it on either the power supply side or the system side. With the memory card and Paradise card reinstalled, I went ahead and powered the machine up with no keyboard, no floppy cable, and no hard drive connected.
The 5150 came right up, counted memory, threw the expected 301 keyboard error and 601 floppy error, and then dropped into IBM Personal Computer BASIC. That was a nice surprise on a machine like this. I tried both video outputs on the Paradise card and confirmed that the top port gave me a working CGA display, while the lower port needed the card’s mode switch set correctly at power-on.
I spent some time testing the Paradise card because that was the real find here. Using RGB to HDMI, I brought up MDA output on the lower connector and then set up composite as well. All three modes worked: CGA, MDA, and composite. The card used a small slide switch on the end to select the mode before boot, and once I had the right profiles dialed in, each output came up cleanly.
With the floppy controller back in place and an XT-IDE connected, I booted from the solid-state storage and checked the drives. The two Tandon FDD55B drives spun up, and I cleaned the heads with a homemade cleaning disk, but neither drive would read a disk. IMD at least showed head movement, but formatting failed with an invalid media or track 0 bad error, so the floppy drives still needed more work.
Since the rest of the machine was behaving, I loaded up Alley Cat and Arkanoid to confirm the video and general system operation under software. CGA output looked good, and a quick recalibration in RGB to HDMI cleaned up some sampling artifacts. I also gave the case a light cleaning with Windex and a paper towel, scrubbed a few small rust spots with a Scotch-Brite pad, and reused the original hard drive faceplate with double-stick tape so the front of the machine looked complete again.
I finished by setting an IBM 5151 monochrome monitor on top and connecting it to the MDA output. The monitor powered right up with a green screen display, and the 5150 ended the day fully booting and running with the rare Paradise card, while the floppy drives remained the only thing left to sort out.
— Aaron
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Timestamps
00:00 – First Look
05:10 – Expansion Cards
08:35 – First Boot
13:42 – Video Card Testing
18:45 – Floppy Testing
23:12 – Games
26:20 – Final Touches