Re: Diagnosing and fixing a faulty Disk II drive

[Delfs <eeastman@gmail.com>]

On Mar 2, 4:50 pm, EricN <e...@neilsonhart.com> wrote:
> I swapped out the analalog card with a known working one and get the
> same R/W errors which are more consistent now (about 3-4 per test). I
> think I just need to break out the oscilloscope and do a full
> diagnostic and alignment if I want top performance.  I've studied the
> Disk ][ Technical Procedures and Sams Repair Guide for the Disk ][,
> but both require an alignment disk (Apple requires the Disk Alignment
> Aid Diskette and Sams requires the Dysan Alignment Disk). Does anyone
> know if there is another method to do disk calibration without these
> disks?

If you have an Oscilloscope, then throw in a likely good disk and
attach the probe to the head.  Watch for the highest signal as you
slowly adjust the head back and forth at track 0.  mark the position
on the cam guide with a razor blade.  Do this at track zero after a
recalibrate by the controller card.  When you think you have it right,
pop on a dozen or so other likely good disks and see how they read
the track.   A utility like copy II+ would be useful to then test all
your disks again at several other tracks to verify alignment by
allowing you to verify signal on different tracks.  Just make sure you
align to track 0 or else you will have major problems.
Of course I am with many other in the belief tha your Apple II drive
should never need alignment unless you have messed with it already.
As a rule They are very hard to get them to misalign without
deliberate action.  LOL that being said, a used drive these days may
have been experimented on.