Mac Classic Project: Part 1

So the work begins…

Ironically, the same day I received my new Mac (the 2019 MacBook Pro) I also received the tool needed to crack open the 1991 Macintosh Classic. I purchased the Classic earlier this month, after years of wanting a vintage Macintosh.

A 1991 Macintosh versus a 2019 Macintosh…

The Macintosh Classic was one of the last Macintosh models to feature the iconic “compact Mac” form factor. The original Classic, introduced in October 1990, was updated in October 1991 with the introduction of the Classic II to use an updated processor (the 68030 compared to the Classic’s 68000) and an increased memory ceiling (10 MB, compared to the Classic’s 4MB.) Finally, Apple released the Color Classic – an entry-level machine that had the guts of an LC II in an updated Classic body with a color display. Some parts of the world got an enhanced Color Classic – the Color Classic II – to mark the end of the iconic form factor. But for us here in the United States, the Color Classic was the end of the form factor.

The Classic suffers from many of the same issues that plagues all vintage computers from this era: failing capacitors and explosive batteries. The second problem is more serious – PRAM batteries are one of the top killers of these old machines. It’s crucial to remove the battery as soon as possible, otherwise you may flip your machine on one time to find that the battery has killed it beyond repair.

The other problem, while not as serious, shouldn’t be ignored. Bad/leaking capacitors can destroy the machine, but they’re typically less of a worry and, in many cases, their damage can be easier to repair. But as with the PRAM battery, it’s good practice to have the machine recapped. Bad capacitors and their leaked electrolyte can cause issues and may render your machine inoperable.

One of the pitfalls of owning a compact Macintosh model like the Classic is they’re much more difficult to work on. Since they have a CRT inside, extreme care must be taken to not be shocked by the high-voltage CRT driving circuitry, or damage the tube.

Another pitfall of owning a compact Mac is they require a special tool to open. Finding a Torx T-15 bit isn’t hard (they’re readily available at any hardware store) but finding one that will reach the two screws located inside the handle is not as easy. First, I went to my local hardware chain store and picked up a T-15 bit and an extender, thinking it was going to work.

The first screwdriver I tried, from a local hardware chain store… a Torx T-15 bit with a 6″ extender

Lengthwise, this solution would’ve worked. However, I learned that part of the bit itself (specifically, where the extender slots into the bit) wouldn’t fit down inside of the hole to reach the screw. Therefore, they went back to the store.

Thankfully, Amazon had what I was looking for: a T15 bit long enough to reach in the handle without needing an extension. After receiving the bit, it was time to crack open the case.

Removing the screws was fairly straight-forward once you have the right tool. But separating the two halves of the case is another story.

As far as I can tell, my Classic has never been opened. So it hasn’t been opened since it rolled off the assembly line in Singapore on May 2, 1991. That’s nearly 29 years.

There are many ways to open these cases, but a lot of wrong ways. You never want to use anything like a screwdriver or knife to open the case, as you’ll easily mar the plastic. People over on the 68kMLA forums recommended a solution that didn’t require any additional tools… push down on the screws in the handle (forcing the front half down) while pulling up on the handle (forcing the front half upwards.)

I tried this technique and needless to say it didn’t work. After trying this for a solid ten minutes, I switched techniques and decided to try using a plastic bicycle tire lever to pry the halves apart. The bottom section of the case was coming apart just fine – it was just the top part near the handle that needed some persuading.

With some light elbow grease and the tire lever, I got the two halves separated. I placed the rear part of the case (sometimes called the bucket) aside. The machine was now open.

Removing the bucket reveals the guts of a Macintosh Classic

Right away, the news is good. The Classic was originally sold in two configurations: a $999 configuration with no hard drive and only 1MB of memory. This configuration wasn’t compatible with Apple’s then-rumored System 7. This machine was the $1499 configuration, which had a 40MB hard drive and 2MB of memory, upgradable to 4MB on a daughter card (which already contained 1MB) and was compatible with System 7. Thankfully, my machine still has the memory expansion card. The memory expansion daughter cards are pretty rare and are not exactly cheap. Without this daughter card, my Classic would’ve been limited to 1MB… which isn’t a lot, even with System 6 and old software.

The memory daughter card… 1MB is already on this card, bringing the system total to 2MB. You can add two additional SIMMs, bringing the system total to its max of 4MB.

The card itself includes an additional 2MB of memory, but can accept two additional 1MB RAM SIMMs to bring the total memory to the maximum 4MB.

The Quantum 40MB hard drive looks factory original, too.

The Quantum 40MB hard drive also looks original.

Now with the memory expansion card removed from the system, I can finish removing the logic board. This is done by removing the two ribbon cables from the hard drive and floppy drives, as well as the main wiring harness coming from the analog board. This main wiring harness is simply connected using a molex plug, but does a lot: it not only carries power, but also carries the video signal, audio signal, and much more.

The logic board simply slides out of the chassis after everything is unplugged.

The Macintosh Classic’s logic board… likely removed for the first time since it was manufactured in 1991

I lucked out. This system has a “Sonnenschein Lithium” PRAM battery that was made in West Germany, instead of one of the infamous Maxell “red bomb” batteries. This PRAM battery looks to be in good condition, but still has to go. It likely has no charge, and it’s known that all kinds of these batteries can be prone to leaking/exploding and destroying the computer – not just the Maxell bombs.

The original “Sonnenschein Lithium” PRAM battery… note the January 1991 date code

The inside of this system looks very clean… very little dust on components.

After removing the battery, I put everything back together. Essentially working in reverse. Don’t forget to re-install the memory expansion card… I did and had to remove the bucket again to install it.

I also had some troubles getting the logic board to line up with the port holes in the case. After having to re-disassemble everything, I found that there were slots on both sides of the chassis that the board slotted into, keeping it straight. Once I discovered the other slots, things went smoothly.

After getting everything buttoned up, it was time to plug it in and turn it on. Did I mess something up? Will it share the fate of the ThinkPad T420? Will there be smoke, sparks and flames?

“Welcome to Macintosh”

After waiting for a couple minutes at the Simasimac condition, the Macintosh booted into its operating system – likely System 6. It worked just like before.

My Plan

With the battery safely removed from the system, I can finally breathe a (slight) sigh of relief and move on to the next part: recapping the board.

As mentioned earlier in this post, vintage computers (or vintage electronics, for that matter – since it plagues more than old computers) are plagued by bad or leaking electrolytic capacitors. These caps are likely the reason for the so-called “Simasimac” condition.

My Classic’s “Simasimac” condition

Ever since purchasing this computer, the Simasimac condition has been getting worse. Sometimes the computer will instantly boot after flipping the switch, but usually it takes the computer 15-30 minutes of just sitting there powered on with the Simasimac condition on screen to finally boot in to the operating system. Which, unfortunately, probably isn’t good on the CRT due to burn-in.

I’m hopeful that recapping just the logic board will take care of this problem. Before releasing Part 2, I hope to have at least the logic board recapped to see if that solves this problem.

I’m on the fence as to whether I should go ahead and have the analog board recapped, too. Just like the logic board, the analog board will eventually need to be recapped. However, removing the analog board is much more involved. Since the analog board contains the driving circuitry for the CRT, you have to discharge the CRT and remove the neck board from the CRT – two things that I don’t want to do. When working with the CRT, you’re working with potentially lethal voltages that can be stored for days – or even weeks – after the computer has been unplugged. The CRT is also extremely fragile. All it takes is one wrong move or being too forceful when removing the neck board to break the seal. Then, it would be game over – the (nearly) pristine CRT in this machine is ruined.

The person who is recapping the logic board said he also has an ADB keyboard/mouse combination that will work with this system. Then I can finally interact with the system.

Way down the road, I hope to purchase a FloppyEmu for this system. That will enable me to transfer files between the Classic and my modern 2019 MacBook Pro. But I plan to do that after getting the system up and working and everything squared away.

However, for the time being, my priority is to get the logic board recapped in an effort to finally get rid of the Simasimac problem this machine suffers from.

One More Thing: The Screensaver

One thing I’ve neglected to mention is the screensaver, which may be the reason the CRT on the Classic has no (visible) burn-in.

I believe the screensaver is Møire, but I won’t know for sure until I can get my hands on an ADB keyboard/mouse and explore the system. As the system is booting into an operating system, I believe you can see the screensaver’s extension loading.

Also, recently it seems that the Mac Classic has been instantly booting. The last week it hasn’t given me any “Simasimac” patterns – but instead chimes and proceeds to boot into the operating system right after flipping the switch. Still going to get its logic board recapped at some point. But thanks to COVID-19 and some personal reasons, the recapping is unfortunately going to have to wait until a later time.

My goal is to have this machine operational (that is – recapped logic board and keyboard/mouse) by October 15, which is the 30th anniversary of Apple introducing the Macintosh Classic, along with the Macintosh LC and IIsi models.

Click here to read Part 2…

Edited 10/5/2020: Cleaned up grammar and some other errors.