800K Floppy Drive Continuous Clicking - Zero Track Problem?

[JDW]

I've been speaking to a gentleman in the comments section under one of my YouTube videos about his 800K floppy drive, and today he shared a video of his problematic clicking head with me here:

As you can see, the optical sensor is in fact working fine.  If it was dirty or clogged, it would not work as shown in the video above.  But as you can see, the head is still trying to move back over and over.

Is this a case of the Zero Track problem?  Does the screw holding the optical sensor in place need to be loosened and the optical sensor moved back slightly?  Or is  the cause of this problem something else?

 

[JDW]

The more I ponder this problem, the more it bothers me.  I don't see how it can be the Zero Track Alignment problem.  If it was that, I would expect the head to stop it's repetitive motion when the head was manually moved forward and then a tool was inserted into the optical sensor (see the video above).  But as you can see, the head continues to move back even when a tool is inserted into the optical sensor.  That tool merely freezes the head location, but the head still attempts to move back.  You can see the worm gear moving the whole time.

Is this a defective chip on the circuit board?

Or does the drive really know where the head is located, and in that case it requires the head to go back a certain number of steps before it stops?  But if that is true, what is the purpose of that optical sensor?  

Hmmm...

 

[JDW]

Currently 110 views of this thread but the only replies are mine.  Surely one among us must own a floppy drive and have seen something similar.  If so, I want to hear from you!

Thank you!

 

[LaPorta]

I personally do not have any recollection of an issue such as this. Seems to me like either something is not being sensed properly, or the signal is not properly interpreted. One suggestion: to make sure not not further damage or strip the head, I'd suggest he remove it and just test the worm gear without the head on.

 

[alexGS]

Yes. I have two 1.44MB Sony SuperDrives with this exact problem. It’s driving me mad. I call it the Dugaduga problem, though that’s not helping in Google searches, I have to admit

The leadscrew stepper motor keeps running until the sensor is un-triggered. Moving the heads by hand (to un-trigger the sensor) will stop the stepper motor.

It seems the fault is that the stepper motor does not reverse direction. It should run the heads out until the sensor is triggered, then reverse direction until the sensor is un-triggered.

Each time the drive is powered up and each time a disk is inserted, the problem reoccurs.

I swapped circuit boards between a third, working drive and the Dugaduga drive; then both drives had the Dugaduga problem until I swapped the boards back. That was too weird to understand. Stepper motor plugs? I tried cleaning them, no change.

Obviously the first thing I tried was swapping the track 0 sensor (ZTS) from a working drive onto a Dugaduga drive - that made no difference. Assuming that finding was wrong, I also cut the three stubs holding the sensor board onto the housing - removed the LED/photodiode, cleaned and replaced, trying different angles of bend. I took apart an old mouse and borrowed the LED/photodiode, fitted those to the sensor, and proved that worked in a working drive. But still no difference in the Dugaduga drive. Measured voltages at the sensor, they are the same.

What did make a difference was turning the stepper motor body and the stepper motor shaft - amazingly on one drive this seems to have an effect (it stops at track 0 when a disk is inserted) until the next time the drive is powered off and on. No difference when tried on the other drive.

Solder joints on these circuit boards seem to be always dull, and they are single-sided boards, so I resoldered lots of bad-looking joints - no difference.

This is the only mention I’ve found online of what seems a rare fault, yet I have two drives doing the same thing.

Thanks
-Alex

 

[max1zzz]

My plus dose this, but the drive doesn't do it in another mac suggesting this is a logicboard issue (unless the fact I tested it on a SWIM based mac makes a difference)

I can also say that it has intermittently done this since the late 80's / early 90's - the Plus had this issue when my dad originally purchased it. Initially it would only do it after ejecting a disk, however in the early 2010's it started happening as soon as the plus was powered on

The fact this issue existed since not long after the mac was fairly new suggests to me this is not a issue with dirt in the drive and reinforces my belief that this is a logicboard issue

I read somewhere years ago that a bad filter network can cause this, replacing the filer network on my plus's board has been on my list of things to do for almost 10 years now so I can't say for sure if this is true or not

 

[alexGS]

My plus dose this, but the drive doesn't do it in another mac suggesting this is a logicboard issue (unless the fact I tested it on a SWIM based mac makes a difference)

Thanks for this info

Two things make this interesting. I have one drive that always works fine with the same Mac Classic logic board that I’ve been testing the faulty drives with, so I seem to have the opposite to you, unless perhaps two drives are affected by the logic board fault and the third is not.

Also, not that it matters but for trivia, you can hear in the sound from the YouTube clip that the drive is being tested with an Apple IIGS