Random Macintosh Classic issues

I thought we were past this point, but it appears the 1991 Macintosh Classic is acting up again.

Since I finished my restoration of the Classic in 2020, it has been mostly reliable for me. After having the analog and logic boards professionally recapped and cleaned, the only issues the machine has given me is a random Sad Mac for a loose memory expansion card and its factory-original 40 MB Quantum ProDrive dying.

The memory card issue was quickly addressed by reseating it in its connector on the logic board, which fixed the problem. And while the Quantum drive came back to life the following day, I decided to play it safe and make the upgrade to solid-state flash storage with a BlueSCSI. Installing the BlueSCSI itself wasn’t difficult, but the process for me wasn’t without its problems.

After being on a hiatus from the vintage computing hobby since spring 2021, my memory (or coordination) wasn’t the best. Likewise, with being limited on space in my current phase of life, my tools to properly do the job have been scattered between here and being in storage. I couldn’t find my static-shielding bags, nor could I find my protective anti-static bracelet. I didn’t let those missing pieces prevent me from installing the BlueSCSI, as I’ve worked on computers (both vintage and modern) many times before without either. It isn’t the proper technique (foregoing ESD protective measures is a cardinal sin for anyone working with delicate electronics) and is fraught with risks, but for such a trivial project it should be fine.

With the BlueSCSI installed, the machine (eventually) ran fine. It continued to run flawlessly until just a couple mornings ago, when it just randomly crashed.

Earlier that morning, the machine had ran fine for several hours. I had done some work in Microsoft Excel 3.0, Aldus FreeHand 3.11 and Aldus PageMaker 4.01. Then, as I wasn’t paying attention, it randomly decided to crash to a striped pattern much like it did before the recap work. Upon a soft restart (using the restart button), it booted into System 7.1 before crashing again. The machine went haywire (glitching with strange patterns flashing on the screen and a randomly squealing speaker) before ending with a Sad Mac screen with code “0000000F 0000000D”. A hard restart didn’t change things… it just did a “chime cycle” — another symptom the machine exhibited before the recap work.

I instantly suspected the aforementioned memory expansion card. As I’ve previously discovered, a loose memory expansion card will cause a Sad Mac and some glitching. So I removed the memory expansion card and reseated it in its connector on the logic board, making sure it was tight. If my diagnosis was right, it should boot up.

It did not.

With the memory expansion card connection ruled out, the fun had begun — tracing down the issue. Because of my limited knowledge and resources, any advanced rework or diagnosis (anything outside a visual inspection or eliminating major parts) would have to be done by a professional.

I started by removing the memory expansion card and disconnecting the BlueSCSI. The machine still didn’t boot, ruling out any issues with those two components.

I then removed the logic board to grab some photos. After re-installing the logic board, ensuring everything was snug, I decided to plug the machine back in to see what might happen.

The Classic’s logic board removed from the computer. Nothing looks out of place. The board was professionally recapped and cleaned back in summer 2020.

Aha! This time the Classic attempted to boot into System 7.1, but wasn’t able to as I didn’t yet install the memory expansion card. With this being a really good sign, I unplugged the machine, installed the memory expansion card and buttoned everything back up. After connecting a keyboard and mouse along with power, the machine booted right into System 7.1 with no issues.

Satisfied with the Classic being back up and running again, I started putting away my tools and editing a video I made documenting the issues and my different attempts to fix it. Another problem fixed, or at least it appeared. The machine could still be unstable, and only time would tell.

It didn’t take long for it to show that it wasn’t as stable as I’d thought. However, it wasn’t glitching out and going haywire like earlier, either.

After a few minutes of displaying the AfterDark screensaver, I tried to wake the machine to test out Word 4.0 and other software. Unfortunately, the machine would not wake. The AfterDark screensaver was frozen with the interrupt command box over it. (The same interrupt command box that randomly pops up with this issue.)

The machine booted straight to another Sad Mac after a soft reboot using the restart button. It wasn’t glitching with strange patterns or noises, though. Even with a hard reboot, the machine went to the Sad Mac with the same “0000000F 0000000D” error code.

While the machine isn’t functional, it’s at least exhibiting similar issues each time with the same Sad Mac error code. Hopefully that will aid in tracking down the problem and allow a professional to quickly get it back up and running.

We shall see.