3.5" floppy drive calibration/alignment

[Rauli]

Is there any information about calibration or alignment (is it the same?) of 3.5" floppy drives?

I have 2 old double-density (720 Kb) drives, and they fail reading disks written in other drives, but work perfectly with disks written in them, so I suppose they have a calibration problem.

One has the "normal" stepper motor and screw in horizontal, but the other (the oldest one) has a bigger motor vertically mounted on one of the back corners of the drive. Anyway, I can't find information about calibration for any of the 2 types.

 

[Stone]

If the machine they're running in supports 1.44 MB HD floppy drives I wouldn't even bother trying to fix them. Just replace them with HD drives.

 

[Chuck(G)]

It is possible to tweak the alignment of most 3.5" drives, but the procedure is very, very touchy. The usual way is to loosen the screws clamping the stepper (positioner) motor and slightly rotate it, re-tighten the screws and test. Repeat ad nauseum. At 135 tracks/inch (5.3 tracks/mm) it's a very delicate procedure.

 

[Rauli]

Well, I'm already using HD drives out of the case (even when the computers only support DD drives).

But but as the 720K drives are the original drives which came with two Philips XT computers, I would like to keep them, specially one whose height is not standard and is the only one which fits in the door.

 

[Rauli]

Rotating the motor doesn't sound very complicated. But I suppose it requires a lot of tries. I'm going to do it. After all, if I make things worse I will still have a mis-aligned floppy drive (the same than now). Thanks.

Edit: Well, 1st I have to get the right screw-driver head...

 

[Stone]

I'm going to do it. After all, if I make things worse I will still have a mis-aligned floppy drive (the same than now)....

Not exactly. You'll have a floppy drive that not only can't read disks from other drives but also can't read disks it previously made itself. IOW, it won't be able to read any disks.

 

[Rauli]

Not exactly. You'll have a floppy drive that not only can't read disks from other drives but also can't read disks it previously made itself. IOW, it won't be able to read any disks.

OK, I will not be able to read test disks that I formatted yesterday

 

[Stone]

I have 2 old double-density (720 Kb) drives, and they fail reading disks written in other drives, but work perfectly with disks written in them, so I suppose they have a calibration problem.

After thinking about your original statement again I'd like to submit this thought. You have two floppy drives that won't read disks made on other systems, right? Will a disk made in drive A read OK in drive B and vice versa? If so I would stipulate that neither of the drives is mis-aligned or in need of calibration. First, I think it is highly unlikely that both drives would be suffering the same problem at the same time unless the computer was dropped some considerable distance and then there would likely be other noticeable problems as well. And furthermore, if they were both out of alignment I seriously DOUBT that they would both be out of alignment so as to be aligned to each other identically. The chances of that are slim to none! So I think we should be looking for other possibilities (especially after you tell us whether the two drives can read each other's disks).

 

[Rauli]

Maybe I didn't explained well: Each drive only reads the floppies formatted in *that* drive, not in the other drive. And they belong to 2 different Philips XT computers, one from 1990 and one from 1991. I'm trying to do something with them now, but they arrived from different sources and they have been stored different time in different conditions. Both drives are manufactured by Sony and both have a Philips sticker outside, but as I explained they are different in size and design (different stepper motor in different location).

 

[SomeGuy]

If they have a worm gear to move the heads, make sure it is thoroughly cleaned and re-greased. Sometimes junk can solidify on those. Also make sure the track zero sensor is clean of any dust.

 

[Rauli]

Do 3.5" floppy drives really have a track 0 sensor? Again, as with calibration, I can't find any real information about it. Just a photo showing a screw and some information about an optical sensor (which I think doesn't apply to floppy drives).

 

[Frank S]

Do 3.5" floppy drives really have a track 0 sensor? ...

It depends on the model and manufacturer, how the track 0 sensor works.
Here is an picture of an older Samsung SFD-321B track 0 sensor.

Frank

 

[Rauli]

And which part is the sensor? The black thing near the capacitor?

 

[MikeS]

And which part is the sensor? The black thing near the capacitor?

No, the black upside-down-U-shaped piece underneath the flexible circuit just above and to the right of center of the picture. One side of the U has an LED and the other a photo sensor, and as the head assembly moves back that little blade interrupts the light.

 

[Frank S]

Here you have two additional picture for better understanding how the track 0 sensor adjustment works for this particular Samsung drive.
The screw for the adjustment you can reach from the drives back and the screw defines the position of the sensor relative to the drive/carriage mechanism.
Frank

 

[Rauli]

Thanks, a lot. I will try again. At least now I know which mechanism I must play with.