4. OUTLINE
OF
MAINTENANCE
• The
following
tools
are required
for
maintenance
of
an
FDD.
4.1
Alignment
Diskette
Alignment
diskette
is
used
for
head
actuator
alignment
and index sensor adjustment.
Use
the
right
diskette
as
shown in Table 8.1.
4.2 Exerciser
The exerciser enables you
to
make all adjustments and inspections necessary
for
an
FDD.
Its
functions
include
the
following.
(1) Seek
increment
or
alternate
tracks
(2)
Read
(but
no
data compare)
(3)
Write
1For2F(AII
"O"sor"1"s)
(4) Head load (5.25inch
FDD
with
optional
head loader)
(5) Recalibration
to
track 0
The exerciser
has
switches and indicators
to
execute a specified
function.
5. DIAGNOSTIC PROCEDURES
5.1
Error Symptom Recognition
Errors
that
occur because
of
the
wrong
operating
procedure,
wrong
programming,
the
use
of
a
defective
diskette,
or
soft
errors due
to
external
causes,
such
as
contaminated
air
and random
electrical noise, are
often
attributed
to
an
FDD
failure.
Unless a visual inspection
of
the
FDD
reveals an
evident
assembly
fault
or
a defect, always
confirm
errors
with
another
good diskette, and
another
known
good
FDD.
5.2 Soft Error Detection and Correction
Soft
errors are
normally
caused
by
the
following.
(1)
Contamination
between
read/write
heads and diskette. This
kind
of
contamination
can be
easily
eliminated
by
the
liner
in
the
diskette.
Please
follow
the
appropriate
procedures
provided
with
the
cleaning diskette.
(2) Random electrical noise,
normally
a
few
microseconds
or
less.
(3) Small defects
in
written
data
and/or
track
not
detected
during
write
operation
may cause
soft
errors
during
read.
(4) Faulty
grounding
of
the
FDD
or
host system can also
cause
soft
errors.
(5)
Wrong
motor
speed
is
another
cause
of
soft errors.
Take
the
following
steps on
the
controller
side
to
recover
from
the
soft
errors mentioned
above.
(1)
Read
the
track
again
ten
times
or
until
the
data
is
recovered.
(2)
If
step (1) above fails
to
recover
the
data,
access
the
adjacent track. Then
return
the
head
to
the
original
track.
(3) Repeat step (1).
(4)
Any
error
that
cannot be corrected
by
the
above procedure
is
irrecoverable.
5.3
Write
Error
If
an
error
occurs
during
write
operation,
it
is
usually detected
during
the
next
revolution by
performing
a read
operation
called
write
check.
To
correct an error,
write
again and repeat a
write
check
operation.
If
the
result
is
unsatisfactory
after
ten
or
more
write
operations, perform a
read
operation
on
another
track
to
determine
whether
it
is
the
diskette or
the
drive
that
is
wrong.
If
an
error
persists, replace
the
diskette and repeat
the
above procedure.
If
the
error
still persists, assume
the
FDD
defective.
If
the
error
is
corrected,
the
diskette
is
defective.
It
can be
thrown
away.
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