Sony MP F75W 11G superdrive with faulty zero track sensor

[petteri]

I received a disk drive but it seems its zero track sensor is faulty. Right after startup it moves to the zero track but doesn't stop there. I cleaned the optical sensor with first air and then IPA but no help. If I block the cut on the bottom of the sensor with a piece of a paper it stops the stepper. But for some reason the arm of the head slider doesn't trigger the switch.

Is there any way to clean this sensor deeper or fix it without spare part? 

 

[Franklinstein]

The T0 sensor may be out of alignment if the head interrupter isn't triggering it, usually as a result of an improper reassembly following cleaning. This is a fiddly job that basically involves trial-and-error adjustments in moving the T0 sensor assembly around to the point that the head assembly stops and that disks are properly recognized. You'll essentially have to move the sensor forward until the head interrupter triggers it, and then insert a known-good formatted disk to see if it can be mounted. If the disk won't mount, DO NOT format it; just eject the disk and then move the sensor slightly forward or back, then reinsert the disk. Repeat until the disk mounts. You may have to manually move the head assembly slightly forward between disk mount attempts so that it re-homes properly to the new position.

If the disk won't mount at all, the head stepper is probably out of alignment, again because it wasn't reassembled correctly following a cleaning. This is a separate but similar process involving rotating the head stepper motor body slightly. Not something to be attempted until it at least tries to mount a disk though

 

[Bendix]

I found this on the net a while ago (dunno where) and was able to fix my drive with it:

„Larry Pina's books often have procedures for aligning floppy drives without lots of the specialized test equipment that Sony requires for a factory calibration. Try checking your local library for The Dead Mac Scrolls or any flavor of Macintosh Bible that he's published if you want a good walk through.

From my memory, the basic procedures (for Sony manual inject only, though it should work on auto inject drives):

You'll need a certified good Mac floppy for testing, either factory produced or formatted on a known-good Mac, to use for alignment. Make sure the disk is LOCKED or you will ruin it and/or screw up the alignment process.

You will need full access to the drive while it is operating so don't try to do this in situ on a SE or Color Classic; you really should use an LC or II of some sort, better yet if you can fabricate a very long floppy cable so that you can have the drive connected outside of the computer and thus have lots of room to work on the drive.

Also, clean the drive first, including the heads, to eliminate dirt as the cause of your problems.

This procedure assumes the drive hasn't been damaged and isn't missing pieces.

For track-0 alignment (generally only necessary if the drive has been completely disassembled and the drive asks to format every disk):

There's a post on the side of the head assembly (an interrupter) on the side opposite of the motor, and it slides into a slot in a black plastic thing (the optical assembly) toward the back of the drive. The interrupter interrupts an optical beam when the head assembly moves into position, and when this happens the drive knows that it is at track 0. To adjust this, mark the current position of the optical assembly, slightly loosen the screws securing the optical sensor assembly, move the assembly slightly forward or back, tighten the screws, and then insert a disk. Repeat the process until the computer attempts to read the disk rather than simply saying it's "not a Macintosh disk." If the head alignment hasn't been bothered, this should be all you need to do as the drive will be properly aligned to track 0 and thus be able to read a good disk. However if the computer has problems reading the disk even after adjusting the setting for track 0, you'll need to adjust the head alignment.

For head alignment (for a drive with new heads, that has been completely disassembled, or regularly has problems reading manufactured disks or disks formatted on other computers/other computers can't read disks formatted in this drive):

There are two hex screws on either side of the stepper motor that drives the heads. Mark the current orientation of the drive chassis to the stepper motor body. Loosen these screws slightly and turn the motor body slightly one way or the other. Insert a disk and wait for the computer to respond. If it says the disk has problems, eject the disk, twist the drive motor body a little more in that direction, and reinsert the disk until the computer reads it reliably. If it instead says the disk is unreadable, try rotating the drive motor in the other direction until the drive attempts to mount the disk. Usually you would rotate the motor body until the drive starts to read the disk well, mark the position, then keep rotating it until it no longer reads the disk, mark the position again, and then rotate it back to a middle point between where it starts and stops reading the disk properly before tightening the screws. This usually ensures the best drive performance and is as good as it gets without getting into crazy test equipment.“

 

[petteri]

I think my original post was a tiny bit misleading. The issue is not really about the zero track alignment. It seems the sensor is not working at all, the arm moves clearly to block the slot on the sensor but it doesn't register it. Instead the stepper keeps rotating, the drive head sledge moves all the way to hard stop and the starts clicking as the hook on the worm drive starts to jump.

If I remove the drive head assembly completely then I am able to stop the stepper from rotating by covering the slot on the sensor. But that requires blocking it very carefully, wiggling a piece of paper wont do a thing. So I assume there is some dirt or goo that reflects IR(?) and fools the sensor.