In the Fall of 2018 I was able to acquire a Macintosh IIsi machine from Facebook Marketplace. This came out of a smokers home and I've been unable to get rid of its smell, so it's never been one of my favorites. I've taken the machine completely apart, washed and retrobrighted the plastics and rinsed the circuit boards with Alcohol, this did help some with the smell. Here's the current state of this machine...
When I purchased the machine, it wasn't running well so I recapped both the logic board and the power supply using the recapping guides from Recap-a-Mac. I didn't do this well; I'll come back to some lessons learned about recapping.
What helped most with the smell was the tip I received that storing the machine with dryer sheets would help to absorb bad odors. Since this was a machine that I didn't need to keep setup I bagged up the machine and monitor in a large garbage bag with a bunch of dryer sheets and stored it for 6 months. This helped alot with the smell so I'll be doing this again as some odor remains.
I pulled this machine out a couple of weeks ago because it's the only machine in my collection that's capable of running Apple's Unix product, A/UX. I had been inspired by this video from Sean at Action Retro to try A/UX. Unfortunately, my IIsi would not power on. I started reading up about issues people were having with these machines and decided that it was most likely that I had not adequately cleaned the Power Supply circuit boards after the recap. I tried alot more cleaning and I was able to get one cold start out of the old power supply. After spending hours troubleshooting the old supply I decided to cut my losses and look for a replacement. I'd been inspired by the idea of putting an off the shelf power supply inside of retro power supply enclosures by an attempted repair of my Tandy 1000 RL HD based on a post on Vogons. I had saved information about a small, low cost Meanwell brand power supply that Jameco is reselling, this supply has the following specifications:
5 Volts at 5.5 Amps
+12 Volts at 2.5 Amps
-12 Volts at 0.5 Amps
The Sony Power supply inside the IIsi had the following ratings:
5 Volts at 6.8 Amps
+12 Volts at 0.8 Amps
-12 Volts at 0.3 Amps
So, the new supply is a bit short on current for 5 Volts, however if you look into the datasheet, if the other channels are running with less load, then the 5 Volt supply can peak at 7 Amps output. I was hopeful that by taking the spinning Hard Disk out and replacing it with flash based storage I would lower the total power consumption of the computer to the point that this power supply would be adequate. (Spoiler alert, the power supply works just fine!)
Another important consideration is the physical size, I wanted the Power Supply to fit into the enclosure of the previous power supply so that the machine looks original from the outside. Here's a picture of the finished product inside of the housing of the old supply...
One of the other challenges I faced with this project was the wiring on the old power supply. I'd cut the old wiring harness off the power supply and tried re-soldering the old wires too the new power supply, but the old wiring is stranded wire that is very difficult to solder on. Eventually I gave up and used Wago spring clamp type terminals to connect the old wiring harness to the new wires.
I connected the obvious wiring:
Red to 5 Volts
Black to Ground
Green to -12 Volts
Orange to +12 Volts
This left the Yellow and White wires unconnected. Through trial and error, I discovered that the Yellow wire needs to be connected to +5 Volts in order for the IIsi logic board to power up. I knew from reading ahead of time that I'd be sacrificing the soft power feature. When this Mac is plugged into power, it is on all the time. I modified the power pass through on the back so that the monitor can still be plugged in on the back, it is no longer switched, it is also on all the time. I also modified a standard IEC power cord to put a switch inline on the cord (using a lamp cord switch), this allows me to power the computer off without unplugging it.
I know this is a bit of a hack, but it is one that is within my skill level. I was willing to make the sacrifice in order to regain confidence in having this machine work when I turn it on. Even with the compromise. I have not modified the outside of the computer and so in my opinion this is an upgrade, although I realize that not everyone in the retro community will agree with me.
Another item that had failed since I last used this machine was the original Apple 40MB SCSI drive, so I've replaced that internal drive with a BlueSCSI. This works well and speeds up the machine a fair bit.
So, after all this hassle, I was reminded that this machine has only 17 MB RAM. Although Apple A/UX 2.0 might run just fine, 3.0 is probably not a good idea till I install a RAM upgrade. The other challenge to getting A/UX on this machine is I'll need to find a way to simulate an Apple Brand SCSI CD-ROM drive. I believe that I'll be able to use SCSI2SD to do this, but I have more research to do. For now, I'm just glad to have the machine back in running order and I'll enjoy running Mac OS 7.0.1 on it.
Do you have any nostalgia around the Macintosh IIsi, or any experiences with Apple A/UX? If so, send me an email, or drop a message in the comments below. Thanks!
