Sony 800k Drive Repairs

[LaPorta]

Hi everyone,

I have a few 800k drives that I would like to repair, and I am pretty sure that they have higher-level electronic issues...things that are not covered in Pina's guides. The drives in question reject any disk that is inserted, and cannot format them. Gross motor controls work: heads move, eject motors function, but nothing else. Anyone have any suggestions as to how and where to start? It would be a shame to toss these things.

 

[AwkwardPotato]

It sounds like the drives may be misaligned. I've been lucky enough to not have to realign any drives so far, but I'm pretty sure you need an oscilloscope to do it.

 

[LaPorta]

At least per Pina, if the heads are misaligned, you won't be able to read disks, but still able to format them and then read them...but they would not work on any other drive. There is an adjustment for track zero, and I fiddled with that but to no avail. These won't even try to format the disk.

 

[Scott Baret]

Have you tried a head cleaner by any chance? I had a floppy drive in an LC do this after putting an old, gummy floppy in it. The cleaning disk did the trick. They're still around, $10 or so most places.

 

[Johnnya101]

Yeah, this sounds like a dirt issue. Otherwise I wouldn't think the disk would be ejected. Plus, misaligned drives are pretty uncommon to find in otherwise working computers... I haven't encountered one yet.

 

[LaPorta]

They’ve actually been sitting on a shelf for a good 18 years or so...and I’m not sure they worked back then, either!

 

[MacintoshMan1999]

Sorry to jump in but, my BOTH of my 800k drives are not working! I'm not sure where to start, The drives symptoms are that the first drives head doesn't move and on the second one the read/write head & disk motor are not moving. So I guess that means no 800k drives for me.

At the moment I've got 4 things I need to fix:

1. Get both disk drives working

2. Get System 6.0.3 disks working (and make copy's)

3. Get the hard drive working (The drive itself and the SCSI ID No. selector)

4. Get the ImageWriter II to advance the ribbon cartridge.

And eventually get:

1. A matching System Saver (Platinum)

2. A FloppyEmu

3. An Apple branded Dial-Up modem (Or get a cord for my current one)

So, yeah.

-Jack

 

[LaPorta]

What is preventing the drives from working? Is there a lack of lubrication? Are the motors trying but unable to move?

 

[MacintoshMan1999]

What is preventing the drives from working? Is there a lack of lubrication? Are the motors trying but unable to move?

The drives seem to be sufficiently lubricated, I'll point out that I did replace the gear in the eject assembly that is almost always cracked/broken. From what I can tell there are two separate motors, one to move the read/write head and another to spin the disk. the motor that spins the disk abruptly stopped working, and the read/write head motor appears to be weak. Are there any fuses or known faults to look for?

 

[Franklinstein]

Some Macs require special floppy drive cables with either a yellow or red stripe and won't work properly without the correct cable. I don't remember off-hand which machines want which cables. Basically the only difference is that one cable has a pin disconnected. If you're having problems you may want to check your cable. Also if the machine is having other issues, such as weird screen artifacts or freezes/crashes or internal hard disk problems, you may want to check your power supply; it may not be outputting enough volts to run everything.

There are three motors on these drives: the spindle motor, the head sled motor, and the eject motor.

The spindle motor is a large Hall-effect DC motor mounted directly underneath the floppy disk spindle. I have only ever seen these fail if something has damaged the spindle where the drive motor meets the disk. You need both the center post (which is fixed in place) and the side post, which is spring-loaded and catches the disk spindle when the motor starts spinning. If the side post is damaged or missing, the spindle motor most likely will be unable to effectively spin the disk. 

The head sled motor is actually two DC motors sandwiched together: one set of coils causes the screw drive to rotate clockwise, the other drives it counter-clockwise. These usually don't fail without physical damage or an extreme build-up of dust. A good cleaning and re-greasing is usually all that is required to get these going again but be warned: removing the head sled motor assembly will necessitate re-calibrating the disk drive when you re-assemble it.

The eject motor is a simple DC motor that drives a reduction gear train. It has position switches in the gear train that turn the motor off once the final driven gear has completed a full revolution and ejected the disk. If the motor runs continuously without ejecting the disk, then one of the gears (usually the first driven gear, a soft orange one) has disintegrated and will need replaced. If the motor doesn't run, it could be that one of the gears is stuck. It's pretty rare for these to fail electrically. Regardless of failure mode, you can still use the drive if you unplug the eject motor assembly from the control board and use a paper clip to eject the disk (only after you drag a mounted disk to the trash or press Cmd-Y, as usual).

 

[pbertolo]

Hi Guys, 

I have this one that is really driving me mad... 

I have since many years a Mac Plus (original Mac upgraded), with 800k drive. I turned it on recently and the drive could not eject, usual rotten gears. So I moved on and temporarily replaced it with 800k unit present in external 800k drive, tested working since forever and including recently when attached to a SE/30. Surprise, nothing happened, able to eject but not able to read any known valid disk.

So I moved my attention to a spare parts donors SE. As I connected the transplanted floppy to the Plus (internal), continuous eject. 

At closer inspection I could detect the red ribbon floppy cable, quite surprising indeed as I don't remember having ever touched it. Anyhow, I just changed it with a yellow.

Now comes the tricky part. When I connect the drive to the Plus via the external unit case, I'm able to read at least some of the floppies prepared with the SE/30. But if I connect the same drive using the internal connector, the same floppy are ejected. Even worse: when I connected the drive (external) to the SE/30, the floppies are all ejected and not recognised.

I can't see any pattern, everything seems to be totally random. I assume it's something connected to the ROM or stuff, but I could not find any hint.

So, any suggestion is welcome! Thanks