View Full Version : North Star Micro Disk System question

May 1st, 2018, 04:16 AM
I've been working on a North Star MDS system for my Sol-20. I have the MDC-A1 controller and the rebadged Shugart SA-400 in the "North Star MICRO-DISK Cabinet (MDS-CAB)".

My drive was set up with the power regulator option to take unregulated +9V and +18V, usually from the power rails of the computer. I've been testing the drive with an external switching supply, and it seems to check out. I don't think the Sol's weaker PSU (compared with an IMSAI other beefier system) would take the additional load very well.

I was curious if anyone out there has an MDS set up with the "North Star Power Supply option (MDS-PS)", which incorporates a transformer, fuse block, switch, etc. in the case?

May 3rd, 2018, 04:08 PM
I guess that answer is no.

Anyway, in the meantime, I've got Mike DeRamp's Virtual Sector Generator going with the MDC-A1. Man, the Shugart SA-400 is a sweet little electromechanical curiosity. The motor spin-ups, head loads, and stepper movements all click away in some little concert. I've tested out CP/M 1.4 and North Star DOS thanks to Mike's website. It's a great resource.

May 3rd, 2018, 05:25 PM
I've got a dual drive box that incorporates what I believe are the N* power supplies and a transformer:


I don't think they're original to the enclosure, as described I had to build mounts for the boards.

May 3rd, 2018, 06:08 PM
I think I may have one? I'm not sure as it is not marked but a fellow collector had a similar North Star dual drive but his case was in a wood outer shell. Mine, of course, is metal.

Could this be one of those drives? http://vintagecomputer.ca/north_star_dual_floppy/

I could open it up tomorrow and take some detailed pics.

May 4th, 2018, 03:38 AM
Thanks! This is great info. I had come across those two pages before, but had totally forgotten about them.

The setup Glitch has is closest to mine, only I have a single drive enclosure. I see you fabricated a mounting bracket for the power board. Mine is mounted to the drive with about 1.25" bolts and standoffs between the Shugart analog board and the power supply board (image attached). The arrangement of the transformer, fuse, switch, and power cord are all helpful to see in the photos. My power board lacks the filtering caps.

I wonder if the vintagecomputer.ca is a later version?



May 9th, 2018, 04:24 PM
I have a generic S100 system (Integrand Research case, Wameco 12-slot motherboard) It has a Northstar MDS-A disk system with a Shugart SA400 drive, with Northstar powerboard, and a Northstar MDC-A3 controller. I know it's not in it's own case, but maybe the image of it mounted in the chassis can be of some help. Here's an older pic I have had of it and can take a newer, larger one if anhyone wants:


The powerboard provided with the North Star Micro-Disk System is bolted directly to the rear of the Shugart floppy drive, providing power to the drive directly from the A/C input coming into the chasis and not from the system power supply.

BTW this disk system was purchased in 11/77 for $599.00

May 11th, 2018, 02:55 AM
That's interesting. It looks like there is a step down transformer and the power board includes the larger filter capacitors. I think I have a better understanding of what North Star was offering at the time. Instead of modifying my board, I think I'll add a small switching PSU in the case and leave the original disconnected. I'm currently running it off an external supply. The drive works great for pushing 40 years.

You purchased the disk system in '77?

May 11th, 2018, 01:51 PM
That picture was taken around the time I got the system, which was in June 2000 from a gentleman in NJ. I'll see about getting a closer picture of the drive and power board this weekend. He was the original builder and he supplied a bit of documentation and history of the machine. What I know of it can be found here: