My Mac SE/30 Part VI: SCSI2SD Installation

In Part V of this series I upgraded the RAM and ROM in the vintage Macintosh SE/30 that I’ve been restoring. In this post, I replace the old dead hard drive with a modern SCSI2SD.

As mentioned in Part II, the hard drive that came in this machine was a 426 MB Segate ST1480N, an upgrade from a previous owner. It doesn’t boot anymore but that’s no surprise – it’s 27 years old at this point. I tried hooking it up to my bridge Power Mac 8600/200, but it didn’t even recognize a drive was connected.

In any case, my plan was always to replace the drive in this SE/30 with a SCSI2SD, which, if you aren’t aware, is a modern device that can simulate one or more SCSI drives using an SD card for storage:

Mounting options

I’ll cover setting up the software side of the SCSI2SD in a later post, for now, the goal is just to get it physically installed and hooked up where the old hard drive used to be. At first glance, it seems pretty straight-forward, but there’s a few minor problems.

First off, the original hard drive screws into the sides of SE/30’s metal drive caddy, and the SCSI2SD only has bottom mounting screw holes. Given that the SCSI2SD is just an exposed circuit board, even if you could mount it, you wouldn’t want the metal caddy to short anything underneath the board.

Secondly, the original hard drive was oriented such that the side with the SCSI port was to the rear of the machine. If I mount the SCSI2SD the same way, then the side with the SD card and USB port will be pointing inside. One of the main reasons I want to use the SCSI2SD is to be able to easily access the SD card to transfer files, make backups, or even swap it out for testing alternate cards. As-is, I’d have to take the case off every time to get to the card, or to connect a USB cable to configure the device itself.

Thankfully, Colin from This Does Not Compute solved both of these problems by designing a custom SCSI2SD Bracket for the Mac SE/30. Instead of mounting to the drive caddy, the 3D-printed plastic bracket mounts to the back of the SE/30’s chassis, and aims both the SD card slot and the USB port out the rear of the case. As detailed in his video, the SE/30 supports expansion cards, and so there’s a small opening in the rear of the case to expose any extra ports those expansion cards might have.

Since I have zero plans for adding any expansion cards, I decided to go with his bracket. He doesn’t sell them but he open-sourced the design, and since I don’t have a 3D-printer of my own, and since this was my first ever time needing a 3D-printed part for a project, I finally got to see what it takes to get someone else to make it for me.

The process was easier than I expected. After getting a little lost looking at sites that handled bulk orders, I found makexyz, an on-demand service that will forward your job to a local printer to print your one-off part. I just uploaded the STL file, kept the default settings, and in a week or so I got the bracket in the mail:

Extending the LED wire

While I waited for the bracket to arrive, I set to solving another problem. The SE/30’s case has small LED in the front that wires to two pins on the hard drive in order to show disk activity. The SCSI2SD does have pin holes for an activity LED, however with the SCSI2SD flipped around, the original wire doesn’t reach.

Wanting that LED to be functional, and not wanting to modify the original wires in any way, I finally invested in a set of various connectors and crimps and made a custom “extension wire”:

I also added a matching header to the SCSI2SD board. Hooking up the LED is very much optional, but I was positively ecstatic to see it flashing when all was said and done. But I’m getting ahead of myself.

Minor bracket adjustments

When the bracket arrived, it came time to actually install it into the machine. However I hadn’t noticed that in Colin’s setup he had removed the original hard drive caddy in order for his bracket to fit. I, on the other hand, intended on leaving the empty caddy in so I wouldn’t ever misplace it.

This was almost a non-issue, except for one tiny little spot where the bracket and caddy intersected. So I busted out my Dremel and cut a small groove in both the bracket and the SCSI2SD board itself:

Installation

With the grooves cut, the bracket cleared the caddy and installed quite easily:

The LED extension wire I made reached perfectly, and looking at the back of the machine, you can see where the bracket mounts to the expansion port slot to expose the SD card and USB port.

But now there was another problem. The SCSI port on the motherboard is near the rear of the machine, very close to the original hard drive’s port. As such, the original SCSI cable was very short, and though it’s kind of hard to see, it’s now stretched to its absolute limit to reach the port on the backwards SCSI2SD.

Not wanting to add any unnecessary strain on the parts, I went and ordered a new longer cable. And by new, I actually mean new! I assumed since SCSI cables aren’t used anymore I’d have to buy an old one, but I was happy to find someone making brand-new SCSI cables in various lengths. It worked perfectly:

The last thing to do was connect power. Now, the SCSI2SD can be powered one of three ways: directly over the SCSI cable (if the motherboard supports it), via USB (if you really want to run a cable there) or via a standard floppy power-cable.

While technically the device draws way less power than a traditional hard drive, and could therefore probably run off just the SCSI cable, I wasn’t sure that the SE/30 motherboard supported and I happened to have a spare Molex-to-floppy power adapter handy. So it was easy enough to continue using the existing hard drive power cable to power the SCSI2SD instead:

With the SCSI2SD installed, my planned hardware upgrades were complete. While there’s still work to be done inside, such as re-capping the analog board and completely cleaning and greasing the floppy drive, for now, it was finally time to close up the case.

I popped off the small door to the rear expansion slot (and taped it inside the case so I wouldn’t lose it), so here you can see the final result from the rear:

I think it looks quite clean, and since it’s recessed inside the case, it’s not immediately obvious that it’s even in there. The SD card sticks out a bit but doesn’t clear the case, so there’s little risk of accidentally bumping it.

That’s it for now, stay tuned for Part VII, where we finally turn to the software-side of restoring this machine.

/jon

Want to read from the beginning? Start at Part I.