One of the retrocomputing projects I’ve been working on lately is finally taking shape — the restoration/construction of a North Star Horizon S-100 bus computer system.
I’ve been building this system up from parts, as the 1977 vintage Horizon chassis — though complete with a battered wooden chassis cover, HRZ-MB-3 motherboard and power supply — had been stripped of its complement of S-100 cards and diskette drives.
The HRZ-MB-3 motherboard supports up to twelve S-100 cards (only six are populated with connectors on my unit), and has a built-in serial terminal interface at the rear. I was able to track down a Horizon ZPB-A2 Z-80A Processor Board, Horizon RAM32 Memory Card and Horizon MDC-A4 Micro Disk Controller from additional eBay auctions. For the diskette drives, I went with Shugart SA-450s which are close to original spec (SA-400).
Next steps involve locating a new fuse holder for the power supply as the existing holder’s retention cover and fuse are missing. I also need to locate an appropriate floppy cable and operating system diskettes.
Perhaps later down the road, I’ll attempt to rebuild or repair the wooden chassis cover as it is in pretty poor condition. The original Horizon chassis cover was constructed of cheap veneer covered plywood (kind of a seventies thing), so repair would involve stripping the old veneer away, filling areas with wood putty and then applying fresh new veneer. It might just be easier to build a new cover to similar specifications out of quality wood, though it would be arguably less authentic I suppose.
Anyway, I’ve had fun putting this together so far; kind of a treasure hunt locating all the parts to form a mostly complete Horizon. Hopefully I can get it to a state where it will actually run once again!
Update: I noticed another NorthStar Horizon chassis has shown up on eBay. This one is missing the motherboard which may be a show stopper for many, but does have the Shugart SA-400 floppy drives, drive cable and a complete power supply. Kind of interesting - not sure why the Horizons that turn up these days are stripped, but I have seen a number of loose Horizon boards as well (including a bare motherboard last month) so it may not be too difficult to rebuild if one is so inclined.