So, I opened up my Apple IIGS 3.5" 800k floppy disk drive to attempt to fix the eject button. On the first try, I simply unplugged the eject PCB, the motor, and the gears from the rest of the drive, and put it back in. Next time I tried to eject the motor actually turned on, but I never stopped. Uh-oh! Not good - but, at least I know that the motor works. I Opened it up again and looked much closer. I learned that not only was the gear stripped (which I can order replacemnts for). Alas, it seems that the PCB also seems to be out of order, as I even manually completed the full 360 degree turn of the gears (b/c one of the gears was stripped) and the little "door"-like mechanism on the bottom of the PCB did not do anything. What do you guys think - is the PCB broken? If so, is there a way to order a replacemnt of the whole electrial eject mechansim? Is it just because the gear is stripped? If so, would replacing it fix everything? Thank you guys!
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So this is the most common kind of failure on Apple 3.5" floppy drive mechanisms, and it is quite well understood now.
The proximate cause of failure to eject is the broken gear, but that gear is designed to break: it sacrifices itself to protect the motor from overheating. The ultimate cause of failure is that the mechanism requires lubrication to operate, and over decades the grease used becomes dried out, sticky, and full of dust.
Since the grease is no longer a lubricant, the drive carriage becomes stuck, and as a result the gear is overtorqued and breaks.
The cure is to fully clean all of the sliding metal parts (top and bottom of the disk tray) with degreaser such as acetone, lightly apply fresh lithium grease to several points of contact, and rebuild the eject motor assembly. The motor should be degreased, fitted with a replacement plastic gear and a few dabs of petroleum grease on the gear tooth areas.
There are videos by the collector "JDW" detailing the process for drive repair. Pay special attention to the carriage that holds the read/write heads, since bending it can permanently damage it.
Repairing and Restoring a Vintage Macintosh Floppy Drive - YouTube
Gear FIX & Molykote LUBE of Apple 1.44MB Floppy Drive [MP-F75W
Tune-O-Gear Ejection FIX & LUBE for Apple 800K & 1.44MB floppy
Got it. The motor still moves perfectly fine, btw. So, you think the PCB is not broken, and some good cleaning and greasing will do the trick? No replacement?
Any proof the gear is designed to break due to excessive moment? According to my multiple observations it breaks due to lack of adequate anti-aging additives in the plastic. Moreover from all plastic gears in the assembly this is the gear with the least moment.
Most of the gears in the train are plastic, but they are predominantly a tough plastic, I don't know for sure the composition but it may be glass filled nylon or delrin. The sacrificial gear is made of a brittle type of plastic such as styrene or ABS, distinguishable by different color. As far as evidence: we aren't likely to ever see direct evidence (design plans, etc) in Japanese from Omron Corp. made 40 years ago, but we can make observations and inferences. The same gear always breaks, and it's after the grease turns into glue.
What little formal information exists includes the Apple specification document 699-0285-A:
Thanks for all the replies, but I'm still wondering - what do I do? Grease, clean and lubricate it? Buy the new gear?
Nothing "sacrificial" here. The motor is of generic type that would sustain dozen of minutes in a fully blocked position. Nothing valuable to protect here. Had it been so dangerous it would have been protected electrically and in a recoverable manner. This gear simply maybe has been manufactured elsewhere or for a different device/at differnet time than the remainig 3. It falls appart in hands from aging without any working mechanical moment. Mechanical "fuses" are usually done in the form of shafts that have thinner well computed diameter in a specific point along their length. The braking is predictable and happens in a designated spot. No mechanical engineer would make a whole gear to act as a protection and break in random places/particles since its breaking leaves debris that can make things worse.
Buy a new gear (Mac effects sells an injection molded one that I prefer over the 3d printed ones), clean the entire mechanism, and re grease it per one of the many videos showing what to do.
I would say there are definately videos to avoid, some folks are idiots and one example includes spraying lithium grease all over the interior of the assembly. There are definately parts (high velocity spin) which shold not be lubricated.
Austin_iigs, common sense doesn't always apply to working with drives. Most of us aren't mechanical engineers and don't have the knowledge and our uninformed minds tend to take what we know from everything else we interact with but this is one case where the common sense things often do more harm than good. Things like lubicating parts may seem like a good idea but when designed to not need lubrication lubricating may momentarily provide a diffrence, but in the long run often creates more problems. The general rule is clean well and wipe down to remove any dust/dirt/debris. After that you're done. Different story with metal on metal moving parts like the disk (un)loading mechanism whcih does benefit from a small amount of a quality libricant that won't gum up.