View Full Version : How to kill a 40 track diskette drive

September 2nd, 2007, 04:46 AM
Today I killed three 40 track double sided diskette drives with a single piece of software.
I am very curious and hope that someone here can explain how that is technically possible.

Here's how events unfolded.

Ran DR-DOS' (Caldera) DISKCOPY.COM on a PC clone computer to create disk image files from master disks, and then create disk copies from the image files.
Creating the image files went according to plan.
But on writing to about the fifth disk copy, the 40 track drive died. Symptom: Reads disks okay but won't write.
Thought I was unlucky and substituted the drive (with a different model drive).
Replacement drive tested okay with read/write operations.
A few more disk copies are created then the second drive fails. Symptom: Makes the right noises, etc. but won't read.
Turned off/on computer. No change.

Not sure what's going on here. Bad floppy controller? Will sort it out later.
Move to my 5170 (which has a 40 track as B:), taking with me a copy of DISKCOPY.COM and the image files.
This time drive failure is immediate when I used DISKCOPY.COM to create a disk. Symptom: Reads disks okay but won't write (same as first drive).

Failure of the three drives confirmed using a third computer.

I can't be that unlucky, surely, but I'm certainly not going to experiment with a fourth drive.

I factor in the failures maybe that I was running DR-DOS' (Caldera) DISKCOPY.COM under MS-DOS rather than DR-DOS.
Maybe my copy of DISKCOPY.COM was bad.
Failures only occured during write operations.

What puzzles me is how the floppy controllers could be programmed/ordered in such a way as to damage the diskette drives.
Anyone got any informed ideas? Or was I just incredibly unlucky?

September 2nd, 2007, 07:33 AM
I don't think that you killed the drive. There are tales of monitors being toasted by bad 6845 programming (and a lack of protection circuitry on the monitor), but I've never heard of a diskette drive getting killed by software.

Here are a few things that I would try:
Check the spindle speed on the drive. Old versions of CopyIIPC from Central Point Software have a /T option which will report the RPM of the drive and is not destructive to diskettes.
Move the drive to a genuine AT and run IBM's diagnostics. Other diagnostic software might help too, without requiring the genuine AT
Clean the heads, carefully of course. You don't want more problems caused by knocking the alignment out. Also make sure the diskettes are not disintegrating in the drive.
Try reading and writing with 'verify' turned on to see if the problem changes or is detected earlier.
Bulk erase the diskettes with a real bulk eraser

You are technically adept so I don't think you got caught by any of the obvious problems above, but maybe something will remind you of something else. If all else fails I have an entire book on diagnosing and repairing floppy drives. :-) (Oscilloscope and diagnostic pattern diskettes are required.)

September 2nd, 2007, 07:35 AM
My suggestion is to power off the computers, remove the drives, and carefully move the drive heads from where ever they are at into the middle of the tracks.

Sometimes drives get "pushed" above track 40 and get stuck there and cannot return to track 0 (the outermost track). I'd not push the heads all the way to track 0 since then when you reattach the drives and power on the computer, you should hear the drive do a "home" operation where the drive seeks track 0. (you may need to enable that function in your ROM BIOS).

If your drives do not "home" on power up, you do indeed have dead drives which is pretty impressive. Software generally cannot physically kill off a drive although it is not unheard of. Usually, it means the heads are wedged stuck above track 40 or sometimes below track 0 which is even more unusual.

The heads should move with some gentle force but not loosely.

Best of luck!

Andrew Lynch

September 2nd, 2007, 07:38 AM
One more thing - it should have been harmless, but I would not have mixed DISKCOPY.COM between OEM DOS versions. DISKCOPY is probably using low level services provided by the DOS-to-BIOS interface that gets installed at boot time, and probably not just built in BIOS services. I would think that it would use the correct software interrupts to invoke DOS services and do what it needs to do, but there may be dependencies on the DOS versions that you have broken by mixing and matching.

If you want to try this theory out, use a diskette imaging problem that you are sure only uses BIOS level calls. Format using the version of FORMAT.COM native to that DOS, then use the diskette imaging program as a diskette copier. If that works, then DISKCOPY.COM is probably not safe to mix and match with.

September 2nd, 2007, 11:27 PM
I am very curious and hope that someone here can explain how that is technically possible.

It's not; check the rest of the thread for suggestions.

I killed two drives using... wait for it... grape jelly. My kid had handled a diskette, I didn't know, and stuck it into a drive. Wouldn't read as head was now coated with jelly. Pulled it out, tried to format a new diskette. Wouldn't format. PUT THAT DISKETTE INTO A SECOND DRIVE TO MAKE SURE IT WASN'T THE DISKETTE THAT WAS DEFECTIVE. Bingo, second drive now coated with jelly.

One drive made a complete recovery. Other drive, can't remember.

Terry Yager
September 2nd, 2007, 11:50 PM
Some floppy drives head is moved with a worm gear on a sprocket. You won't be able to move the heads on such a drive without breaking sum'n, so beware. Also, check for viruses. I recall going thru a full 15 rounds with a virus several years ago that had a similar effect. It very convincingly emulated a failed floppy drive. I'm not certain, but I believe it was one of the ANTICMOS family.


September 3rd, 2007, 04:30 AM
A lot (repeat: lot) of head cleaning cured the problem.
It very much looks like I've encountered several badly aged diskettes.
I should have thought about that possibility myself - kick, kick, kick.
I guess the suddenness of the third drive failure threw me.
Thanks for all suggestions.

Dwight Elvey
September 3rd, 2007, 08:29 AM
Check supply voltages.
Of course, it could actually just be bad luck.

September 3rd, 2007, 08:59 AM
I win the prize!