Sharp FDD-412A - Page 91

FDD412A/B
5.2
Media-Related
Troubles
5.2.1 Outline
Today,
the
floppy
disk
is
filling
the
major
role
as
storage
media
for
small
business
computers,
various
terminal
devices
and
peripherals.
This
trend
may
be
a
natural
choice
as
a
result
of
the
disk's
various
advantages
including
easy
handling
and
random
access
capabilities,
unlike
conventional
media
such
as
punched
cards,
paper
tapes
and
magnetic
tapes.
However,
inadvertent
handling
often
results
in
damages
on
the
recording
surface;
it
consists
of
fine
oxide
powder
bonded
with
special
bonding
agent
(binder)
on
a
thin
polyester
film
(about
75
um
thick).
The
disk
is
protected
in
a
jacket
composed
of
bonded
fabric
(liner)
coated
with
vinyl
chloride.
Because
the
floppy
disk
is
mounted
on
a
FDD
together
with
its
jacket,
the
quality
of
the
jacket
also
affects
performance.
There
are
numerous
floppy
disk
manufacturers
in
the
world.
Small
but
noticeable
differences
are
recognized
in
physical
and
electric
proper-
ties
from
one
manufacturer's
product
to
another.
Media-related
troubles
are
generally
divided
into
four
categories:
(1)
Troubles
due
to
inadvertent
handling
(damage,
bend,
etc.)
(2)
Troubles
attributable
to
production
prsebss
(3)
Defective
device
by
which
to
write
data
into
medium
(4)
Defective
device
by
which
to
read
data
from
medium
Troubles
that
fall
in
category
(1)
are
particularly
frequent.
One
study
reports
that
60%
or
more
of
all
troubles
in
a
given
period
fell
in
this
category.
When
a
data-related
error
occurred
while
an
FDD
was
being
used,
it
often
proves
difficult
to
determine,
from
the
user's
explanation
alone,
whether
the
cause
is
in
the
drive
or-on.mediun.
To
separate
the
trouble
positively
to
the
drive
or
to
the
medium
re-
quires
observing
the
actual
status
of
magnetic
recording.
5.2.2
Troubleshooting
Procedure
(1)
Read
out
a
waveshape
from
the
defective
portion
on
the
medium
in
use
at
the
time
of
the
error.
(2)
Find
a
similar
waveshape
from
the
pictures
in
5.2.3.
(3)
Find
in
5.2.4
the
typical
failure
with
its
description
corres-
ponding
to
the
picture,
and
determine
what
caused
the
error.
5.2.3
Pictures
of
Normal/Abnormal
Readout
Waveshapes
(1)
Waveshape
observation
points
CH1 : TP1 (READOUT 1)
CH2 : TP2 (READOUT 2)
EXT TRG: TP11 (INDEX-P)