Re: Malfunctioning 5.25" drive: please assist

[rubywand@aol.com (RUBYWAND)]

In article <50cup5$i12@zot.io.org>, crownmi@zot.io.org (Myles Fudge)
writes:

>....
>This drive is a third party disk II drive, connected to my IIe clone
while
>I'm testing it.  I also have an original Disk ][ drive that I'm using to
>compare notes with.  The Disk ][ drive is in near perfect condition.
> 
>The 5.25" clone drive receives power and spins, however it does not
>read the disk.  My Apple reports an I/O ERROR when I attempt to
>CATALOG a freshly formatted 5.25" disk with the bad drive.  The disk, 
>however, works just fine in my Disk ][.  I have found that once I've 
>attempted to catalog a good disk in the malfunctioning drive the disk no 
>longer works in the Disk ][ drive.  It seems that the malfunctioning 
>drive is damaging the disk.
> 
>I am using Locksmith to check the disk's speed and Locksmith indicates
>that the drive's speed will not come within tolerance.  That is, the
>indicated speed is either too slow or too fast, and never within range
>of acceptable drive speed.  I've turned the potentiometer inside the
>drive and it sounds like the drive spins from slow to fast smoothly -
>with no jump from slow to fast.  I cannot recall the program that
>indicates drive speed in numbers, so I'm going with Locksmith's HIRES
>speed graph.
> 
>I've physically inspected each component inside the drive
>and they don't look or smell burned out.  I haven't gone through the 
>trouble of testing any or each of the components out-of-circuit.  No
>inordinate amount of heat is coming from any component.
> 
>All wires and connectors appear to be in place, the diskette I'm using is
>not write-protected, and Locksmith ceases to spin the drive when I've 
>opened the drive door during the speed test.
> 
>There is a pressure switch on the underside of the drive that is
>depressed by a plastic arm when the stepper motor moves the read/write 
>head to the track 0 position.  At this point in time, the drive is
>in the track 0 position with the switch depressed.
> 
>Where do I go from here? ....

     The fact that the drive bombs diskettes when you attempt just a
CATALOG is not a good sign. One possibility is that some circuit is
flipping ON a WRITE signal at odd times.

     Before looking for something arcane, open the drive and examine the
head. A worn or badly gunked-up head might scratch a diskette. For sure,
it will not be much good for R/W.

     If the head is clean and does not seem overly worn, another suspect
is magnetization. If, somehow, the head has become magnetized, then it may
damage diskettes and will not reliably R/W. You can demagnetize a disk
head using a tape head demagnetizer. (Or you can remove the drive module
from an old-style clock motor and use the AC field at the poles.)  Move
in-out slowly near the head.

     I do not know about the micro-switch in your drive. If the mechanics
seem solid (e.g. no arms or levers are bent or missing),  then,
supposedly, the micro-switch button is being depressed at the right time.
This does not necessarily mean that the switch is working. First, the
mechanism may pushing the button IN, but not far enough to 'click' the
switch (or it may not be permitting the button to un-'click' at the right
time. 

     It is also possible that the switch is broken. You can diddle the
switch button and use an Ohm meter to check that the switch is not stuck
ON or OFF.

     The program that shows a drive speed number is Copy II+. Many users
forget this because you must select "Verify" from the menu before
discovering the "Drive Speed" option. This check will over-write data on
the diskette you use.
 


>....
>P.S.  Whoops -- my apologies for not limiting the length of my text to 70

>      characters, or so, in advance.


     Well ...., okay. But, if this happens again, you're in _big_ trouble!


Rubywand