The ComputerHobbyShop Web Blog
(Post updated on 10/31/2025 by the original author, Richard A McFarland, aka RAM)

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A Mac Plus Resurrection Story

I recently acquired a vintage Mac Plus from eBay, which I saw was unfortunately in a terribly rusted condition
both outside and later, as I was sure, also inside. I tried to bring it back to life, but needed some effort and patience.

First Steps

1st I had a lot of cleaning up to do. I had bought this Mac Plus after seeing it was terribly rusted on the outside, and when
I took it apart, I saw what I had expected--it was also rusted inside due to the battery corrosion that had leaked acid down
and rusted the metal frame. Capacitor goo had also leaked onto the analog board and ran down to the bottom of the case.

I noticed the rust and corrosion in the auction pictures and
I knew it was the perfect challenge for #MARCHintosh 2025.

It was time to work on the plastic case and the metal frame.

I started on the metal frame, which was the scariest looking of all the parts.


The frame is a support for analog board, also houses the floppy drive, and stabilizes the front of the Mac below the CRT.
See a picture of the frame before removing it from the case. Notice the big ugly fan that was held in by bailing wires!



To clear off the rust on the metal frame which supports the logic board, I used a wire wheel brush set.



After I cleaned, wire-brushed, painted the frame and let it dry, I put it in the Mac. It turned out really nice looking too.

Then it was time to work on the logic board...
... it was a mother board that no child could love, lol.

I cleaned the logic board with very hot water and a scrubbing brush, then I used used my
YTL-015 1500 Watt Hot Air Paint Drying Tool and applied 70% rubbing alcohol for a
second scrubbing, as that was all I had in the shop. I used my tool again to get it
totally dry and I stopped just short of watching the plastic parts start to smoke.

After I put it back together, I was eager to see how bad the componets were in a live power up test.

The Initial Problems After Cleaning It Up and The Reassembly

See below the analog board/power supply before cleaning it.

Even though I had cleaned everything, at 1st boot the Mac
would not ding or chime, nor show anything on screen.

I was not ready to replace the caps nor re-solder any cold joints just yet, so I had decided
to switch out the analog board with a known good power supply on a known good analog board.
Now when I booted the Mac, it started with a ding, (the Mac Plus diagnostic chime was a good sign).



But if you zoom in, maybe you can see, it only showed the Happy Mac in a small box on the screen.

I had never seen the Happy Mac trapped in a small jail cell before. It was strange how it appeared like that,
because bad memory will typically act different, but since it did chime, this told me that maybe the memory
was not configured right as the image would not fill the screen, or progress booting further past a Happy Mac.

Here is a short video demonstrating what bad RAM can act like.

In the clip I mention video screens are a sign of bad RAM, but I later also got an error code "0F000D" too.
It was just not filmed when it happened and I could not get the error code to come back a 2nd time.

The Solution Was Getting Closer Now

So the logic board needed further inspection. Even though the 4 RAM chips had some green corrosion
on them before, I had earlier cleaned the contacts with a brush and they looked OK. Suspecting mismatched
RAM sizes, I decided to take out the board and looking again more closely with a magnifying glass, I saw that
the logic board revealed the R8 resistor was cut, but was not bent very far back, ... see the R8 zoom in below...



A cut R8 was signifying a 4 MB configuration had been attempted earlier. My suspecting mismatched RAM was
right on the mark, as I'm sure a 4 MB configuration had been attempted by a previous owner and so troubleshooting
and looking more closely, an exam of the RAM included two TM4256GU8 chips. The Copilot AI said
these were 256 kilobits each. I also found two Micron MB8C8024M-M8 chips, which were not easily
explained by the AI, but even with that information missing, I suspected these two chips were 1 MB each.

Since I only got a chime and a happy Mac, it could mean that the last person to work on this Mac did indeed mismatch
the RAM sizes. I replaced the two 256k chips with two known good 1 MB chips. Success! The Mac booted up and
displayed 4,096K, confirming an issue of mismatched RAM sizes. Now it works fully with 2 MB + adding 2 MBs more.

The Final Steps

Now all I need to do is recap the original analog board, and since this Mac was also without a working floppy drive,
I at least know it will boot from the Floppy EMU. After I recap the analog board, I'll remove the donor one I used
for diagnostics and install the recapped unit and test boot the Mac Plus with SCSI and re-run diganostics again.

Final Thoughts

This project has been a labor of love, and I'm thrilled to share it here.
I got this Macintosh Plus knowing it needed work and restoring, but it wasn't
until after I got it that I saw just how bad a shape it was in and what was needed.

I was sure it would not boot and I really didn't expect the logic board would ever work again!

I enjoyed working on this vintage Macintosh Plus computer. It was a true adventure,
... a surprise restore and preservation of a piece of computing history ... a rewarding challenge.

End Game Notes:

Posting fun restoration projects requires website hosting.
If you enjoyed my post, please see my 17 inch Laptop offer below...

HP Envy Bang&Olufsen 17 inch 2.4 GHz Turbos to 3.0 GHz
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When you buy from me on eBay you're supporting my
green earth-friendly restoration projects and then
I'm able to post more, so thanks for your support!

I also create videos to post at @ComputerHobbyShop on YouTube.


This is post was 1st published for #MARCHintosh 2025 and is a re-post, updated 10-31-25


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