New old stock floppies loosing data...

[Adventurer]

Ok, I think I have finally solved the mystery of loosing data - it appears that the "Bad" - Maxell floppies tend not to spin, when the drive is locked, resulting in various type of read errors. First I was suspicious, when noticed, that they would often start to read data, if I turned the floppy by hand before putting it in the drive.

Had to play with some screws on the drive itself to make things better. Still, two other floppies, not made by Maxell were spinning freely before adjustment, so I believe they simply have too much friction between inner and outer area of the floppy disk.

 

[KC9UDX]

There are two things that can cause that: either the bearing material inside the disk has deteriorated (this is the most common failure that I find with 5-1/4" diskettes) or the cookie is too slippery at the hub. (Of course, it's probably a combination of the two.) There are various ways to deal with the latter, and you have found one.

I wonder if there are different cookie thicknesses. If you have a micrometer, it would be interesting to see if the different disks you have are different in that way.

 

[Adventurer]

There are two things that can cause that: either the bearing material inside the disk has deteriorated (this is the most common failure that I find with 5-1/4" diskettes) or the cookie is too slippery at the hub. (Of course, it's probably a combination of the two.) There are various ways to deal with the latter, and you have found one.

I wonder if there are different cookie thicknesses. If you have a micrometer, it would be interesting to see if the different disks you have are different in that way.

Well, the material itself looks fine, but I can not really measure the thickness of the cookie, since I do not have a micrometer. However, given the fact that not only the floppy stops spinning, but the spindle itself, it is not slipping, it just stucks...

 

[Stone]

There are five parameters that are measured during a thorough floppy drive test procedure. They are:

Alignment
Clamping
Hysteresis
Speed
Track Zero

You may have a clamping problem.

A floppy disk is formatted into individual tracks laid down in concentric circles along the media. Because each track is ideally a perfect circle it is crucial that the disk rotate evenly in a drive. If the disk is not on-center for any reason, it will not spin evenly. If a disk is not clamped evenly the eccentricity introduced into the spin might be enough to allow heads to read or write data to adjoining tracks. Clamping problems are more pronounced on 5¼" and 8" drives, where the soft mylar hub ring is vulnerable to damage from the clamping mechanism.

 

[Adventurer]

There are five parameters that are measured during a thorough floppy drive test procedure. They are:

Alignment
Clamping
Hysteresis
Speed
Track Zero

You may have a clamping problem.

A floppy disk is formatted into individual tracks laid down in concentric circles along the media. Because each track is ideally a perfect circle it is crucial that the disk rotate evenly in a drive. If the disk is not on-center for any reason, it will not spin evenly. If a disk is not clamped evenly the eccentricity introduced into the spin might be enough to allow heads to read or write data to adjoining tracks. Clamping problems are more pronounced on 5¼" and 8" drives, where the soft mylar hub ring is vulnerable to damage from the clamping mechanism.

The only problem is with Maxell disks - Verbatim and Xidex rotate freely without any problems. I did adjust clamping strength (released a little), so Maxells now do spin freely (but data problems still remain into some extent, so they are still no good).

 

[KC9UDX]

But don't forget, the Maxell disks may be the ones that are made to specification.

The others could be more forgiving, or, out-of-specification in your favour.

Unless you can measure the torque needed to turn the disks, and measure the cookie thicknesses, and find specifications for these parameters, you won't know which is which.

In either case, if you get the Maxells to work, you've increased the number of disks and disk types that your drive will work with.

 

[Adventurer]

But don't forget, the Maxell disks may be the ones that are made to specification.

The others could be more forgiving, or, out-of-specification in your favour.

Unless you can measure the torque needed to turn the disks, and measure the cookie thicknesses, and find specifications for these parameters, you won't know which is which.

In either case, if you get the Maxells to work, you've increased the number of disks and disk types that your drive will work with.

Still, this has improved reading of them, but one document diskette died completely, and unexpected - and I can not even recover a single sector of data from it. So I hope Maxell's are not the ones to made according to specification. The plastic is much thinner, much more fragile than two other brands, it just feels cheaper made.