Sony Superdrive stopped working

[powermax]

Hello crews,

yesterday I turned on my Power Mac 6100 and noticed that the floppy drive has suddenly stopped working. Last month, it was fully functional - I could read, write and format floppies just fine.

I've disassembled the computer, reseat the cables and checked for the presence of all required voltages (+5V, +12V and -12V). Anything looks good.

The drive in question is Sony MP-F75W-12G (Apple-Nr. MFD-75W-01G). When I insert a disk the disk motor spins on for 2 seconds. Then it stops and nothing more happens.

Any ideas on what the cause for this failure could be?

Is there any documentation on how to disassemble, clean and repair this drive?

Thanks in advance!

Cheers

Max

 

[mactjaap]

Maybe your stepping motor died. It is the middle metal one.

Just to be sure. What if you boot from an other drive and insert a disk?

 

[powermax]

Maybe your stepping motor died. It is the middle metal one.

Thank you, I'll check it out.

Booting from HDD works but the OS doesn't recognize any disk in the floppy drive...

 

[powermax]

Maybe your stepping motor died. It is the middle metal one.

I checked the stepping motor. It's a bipolar Minebea 08BJ-H031-41 with 4 wires. Each of the two windings has a resistance of approx. 90 Ohms. I was able to drive the motor away from the zero track sensor by alternately attaching a 9V battery to the windings and switching the polarity.

After that, I reinstall the drive in the computer, powered it on and pressed on the inject microswitch with a screwdriver. The disk motor started and the head quickly moved to the track 0. That's good news.

Bad news: when I insert a disk the drive motor starts and then immediately stops. The Mac doesn't see any disk in the drive...

 

[johnsonfromwisconsin]

I get into this hobby intermittently.

The biggest issue that makes me want to just put it all on eBay is these damned floppy drives.  They all just stop reading or writing. I've had half a dozen fail after only limited use and even after cleaning don't seem to want to cooperate.  

 

[mactjaap]

That is a thorough check!

Stepping motor is fine.

Yes. These drives can be a pain. Thank got I have a FloppyEmu.

But, I also don't like to give up and hope for you there will be advise what to do next. I'm out of clues for now.

 

[techknight]

You know, All of my floppy drives work. Sure I had to do some maintenance on them to get them working, but so far they all work except for 1 which needs gears that broke. 

I have noticed alot of people with floppy issues lately. 

Keep in mind, floppy drives use a magnetic head, and the head gap can wear depending on how often the drive was used. 

If the drive was beat to hell, used and used and used over and over again, the head will wear to the point where it becomes intermittent, and worse, to the point where it wont recognize the disk formatting, and attempting a format fails on all disks. Bad head. 

Anybody collecting 8-tracks, or cassettes and cassette decks will know this. If everything sounds muffled, and lacking highs with the azimuth adjustment having no effect is a worn head. 

Good heads should have bright crisp sound on both channels. faded, muffled sound = worn bad head. 

Same goes with disk drives. if the head wears, the high frequencies fade which means the decoding circuitry will have a harder and harder time being able to regenerate the clock and bits. 

the other symptom is the drive not being able to read/format disks, and the drive is actually "damaging' disks meaning after inserting into a non-working drive, its not detected anymore by any other drives and possibly errors on track 0 bad during a format on other systems. This is the result of a magnetized head. A head demagnetizer will fix that right up. 

 

[powermax]

My floppy drive is actually fine! I just tested it with another PowerMac 6100 board. ;D

The funniest part about it is that the drive works after it has been completely disassembled and then reassembled. No alignment or tuning was ever necessary! Well, I put some markings on the stepper motor and the track 0 sensor before disassembling so the unit could be easily reassembled. That means that the stepper motor must have some alignment tolerance which is a good thing!

Now I have to find out why my old board fails. I hope that's only a corrosion somewhere and the SWIM III chip isn't fried. Otherwise I'll have to replace it which isn't funny at all... >