Re: Alignment disk and diagnostic program - ][+ and //e

[bill_h <bill_h@sunsouthwest.com>]

Michael J. Mahon wrote:
> 
> It is apparently worth saying again:
> 
> THERE IS NO WAY TO MAKE A USEFUL COPY OF A
> HARDWARE ALIGNMENT DISKETTE BY USING AN APPLE DISK DRIVE.
> 
> The signals written to such a diskette are not digital signals.

Well, the first statment is true. The second isn't.

The test disk is made by writting to the disk with a NON STANDARD
disk drive. One that has a stepper moter controlling the ALIGNMENT
PARAMETERS THEMSELVES!!!

What they do is write, for example, let's say 9 sectors, each with
slightly different alignment. The FIFTH (middle) one is dead on.
The four before that are +4 'units' off; +3 units off; +2 units off;
and 1 unit off. The following four likewise increasingly MINUS one,
two, three, and four ''units'' off. Actual numbers or degrees for
units un-important.

Then there will be TRACKS where a sector is dead on, but before and
after it are sectors displaced from 'dead on', by increasing amounts.

When you read a track (alignment; track centering, etc) you get
one or more 'good' signals, and knowing the SECTOR NUMBER can tell
which sector they're coming from. Likewise, you DO NOT get signals
from one or more sectors, and you know what they were set to, also.

So, taking all the possible (useful) alignment factors into
consideration
by reading a track meant to 'measure' where exactly YOUR DRIVE is most
strongly responding tells you whether your drive is ''aligned'' to the
''standard'', or if it's off, which way (so, hopefully, you can loosen
something and CORRECT it).

The key to all this is a diagnostic disk that not only has SOME info
written absolutely PERFECTLY aligned, but ALSO, some information
recorded at KNOWN MIS-ALIGNED settings.

NO STANDARD DRIVE CAN DO THIS!!!

Even if YOU could write a sector, loosen something and shift a carefully
measured amount, tighten, write another sector; loosen, shift, tighten,
write, etc your way through what must be a hundred CAREFULLY CALIBRATED
SETTINGS, imagine the time it would take!

It's just cheaper (and, realistically, more accurate) to simply buy one
of the Dysan or other precision made alignment disks.

Copies of them are worthless and tell you NOTHING.

Bill
Tucson