Mac Plus Repair – The Continuing Saga

reviving an Apple Macintosh Plus

The Story So far

mac_thumbSo, for what seems now like an eternity, I have been working on the old Macintosh Plus. I certainly feel like I’ve been through a war with this computer to say the least. Any of you following my blog with know I have spent some time restoring this classic computer. At the beginning of last year, the display died, leading me to fault-find the analog board and replace component after component, finally getting the beast to power up, only to have the floppy drive start jamming up. It really has been a labour of love and not one I should care to repeat any time soon.

No time to shake your floppy disk

After 25+ years, the lubricant inside the floppy drive of the Plus has seen better days, now resembling a dried goo. So, time to take the floppy drive apart. Now if you have a Plus and you have read horror stories about people messing up their drives, it is probably because they didn’t do it properly. It actually isn’t that hard, so long as you take your time and pay attention to what you are doing. Before you start, a good idea is to consult the tutorial on the 68kmla forum which does a pretty good job of showing you how to service an 800k floppy drive. Again, pay attention to what is says. There are springs inside the drive, which if pulled to far, will loosen their tension and result in your drive being permanently buggered.

Cleaning drive

Cleaning the gunk out the drive, what fun!

So after taking the drive apart, I used silicon grease to lubricate all the areas that needed doing. I really thought at this point that everything was going pretty well, which is usually when disaster strikes! When I rebuilt the floppy drive, I couldn’t help but notice the whole mechanism felt stiff and not smooth at all. Stripping it down once more, I reapplied more grease and still the whole mechanism felt like it was grating. It couldn’t be grit or dirt as I had cleaned the whole thing out, so that left me thinking perhaps it was the lubricant I was using. I had bought silicon grease after reading someone one the 68kmla forum recommending it. Removing as much as I could with an alcohol swap, I used some wet lubricant, designed for bicycle chains. I’ve used this on a front door lock which was sticking and boy did it work. A year on and the lock still works super smooth.
If it worked for the lock, I was hoping it would work for the floppy drive. Sure enough dropping a few dabs, the drive ran back and forth much smoother then before. With this promising start, I reapplied fresh lubricant to all the needed areas and reassembled the drive. Unlike my first attempt the Plus did not lock up while trying to eject a disk, it ejected it each and every time I inserted a floppy. Time for a big sigh of relief right?

Spitting out a floppy

Spitting out a floppy

What no power?

After rebuilding the system and leaving the lid of, I tried firing up the Plus to test it before closing the lid. Anyone who works on their own computer, will tell you never to put the lid on until your completely sure, without a doubt that the damn thing is working, for the exact reason I am about to describe.
Thinking nothing could go wrong, I flicked on the power switch and the Plus did not power up, instead it made a slight fizzle and then nothing. Unlike previous fizzles, this one was like the CRT discharging, which was odd. Turning it off and wearing protective gloves, I wiggled the lead linking the analog and logic board together and tried again. Still nothing from the Plus. This was getting frustrating. Why was it not booting? I hit the side of the analog board and suddenly the Plus fired up, which meant a dry joint.


Getting the drive to eject was easier then it looked

Reflowing some of the caps and joints that I thought looked suspicious, I managed to get the Plus working once more. I still suspect a component to be the guilty party, but I wont know that until I’ve used the Plus further.

For now however, the old beast appears to be working.

Thanks has to go Prof. Thomas H. Lee for his amazing PDF guide (which I will be doing a blog about very soon), Thrashbarg for his overwhelming help when problems far exceeded my electrical knowledge, and finally all the guys on the 68k Macintosh Liberation Army Forums.

For now, keep on geeking!
Today’s blog was written on a Classic Macintosh