Multiple Topics...

From: Tony Duell <ard_at_odin.phy.bris.ac.uk>
Date: Tue Aug 19 11:43:31 1997

> doesn't work, you need the narrower write head. What you will see is
> the additive components of the signals where the head overlaps the tracks.

Not at all. What I was planning on recording (on a totally blank disk) was
:

  ==== ==== ====
       ==== ====


Where the ==== is a burst of data and the centre-line of the desired track
was along the middle of the 2 patterns. The read head output will only
reply the 2 bursts at the same amplitude (assuming they're sufficiently
separated, which will take some experimentation) if the head is following
that centre-line.

> The can be the sum or the signals, if not in sync there will also be
> differences due the phases at a given instant. Also do not discount the

There's no way the head will be reading bits of the 2 recorded tracks at
the same time. So cancellation does not apply.

> effects of the tunnel erase portion of the head slicing off the adjacent
> offset tracks.

Firstly I'll be gating the WG signal, so I'll not be erasing my
carefully-recorded track, and secondly, I am probably using custom
electronics so I can remove the erase signal altogether if it causes
problems.

 
> <The older SA800's used entirely standard logic, so it's not worth taking
> <parts from an old one. SA850's used custom chips in the read/write
> <circuit, and later SA800's (according to my service manual) used one big
> <custom chip :-(. I guess then you have to get spares from old drives.
>
> Sometimes it's easier to swap a known board that troubleshoot.

Hmm.... By the time I've found where the fault is (i.e. proved it to be on
a certain board), I'm pretty close to the defective component anyway. The
SA800 is not exactly difficult to trouble-shoot, and I do have the
official service manual.

>
> <Getting _new_ 8" drives is next-to-impossible, and if you use a
>
> True but, there are used and then there are USED. The later being one thats
> seen umpty years of 24x7.

I know of only one UK supplier, and they want \pounds 295.00 (!) (nearly
$500.00) per drive. And my experience of this company, based on a friend
buying a 'used but good 5.25" drive' which came with a worn-out spindle
motor, a fault on the speed control board and another on the logic board
means that I'd rather not deal with them. Quite simply, it's cheaper and
less hassle to rebuild what I have.

> Allison

-tony
Received on Tue Aug 19 1997 - 11:43:31 BST