Hitachi MX-W50 - Servicing Precautions; Laser and Mechanism Handling; Part Replacement Precautions

MX-W50
18.
19.
20.
(1)
(2)
Checking
the
Object
Lens.
(Fig.
9)
Make
sure
that
no
dust
or
grime
gets
on
the
object
lens
of
the
lens
actuator.
After
a
long
period
of
use
it
is
possible
for
this
lens
to
get
dirty
or
dusty.
In
such
a
case
try
to
clean
the
front
surface
of
the
lens
with
a
cotton
applicator.
Laser Malfunction Check
The
laser
normally
operates
on
a
current
of
40
—
80mA.
If
the
laser
circuit
is
measured
and
shows
a
current
of
100
mA
or
more
it
may
be
assumed
that
the
laser
is
defective.
Things to Keep In Mind During Servicing
(Fig. 10)
Regarding the Semiconductor Laser
The
semiconductor
laser
is
extremely
sensitive
to
elec-
trostatic
disruption
and
surge
current.
Be
very
careful
not
to
allow
the
hand
or
any
tools
ever
to
come
into
contact
with
the
terminals
of
either
the
laser
or
the
flexible P.W.B..
Furthermore,
the
Current-Light
Intensity
Characteristic
once
a
certain
amperage
threshold
is
exceeded,
rises
sharply
(as
can
be
seen
in
Fig.
10).
This
current
threshold
is
slightly
different
for
each
laser
unit.
Consequently,
during
operations
such
as
the
replacement
of
the
Unit
Mechanism
Assembly,
when
setting
the
intensity
of
the
laser
be
sure
to
turn
the
Semi-variable
Resistor
VR901
as
far
to
the
right
as
it
will
go
to
set
it
off
once,
and
then
raise
the
current
to
the
level
which
is
specified.
Handling
of
the
Unit
Mechanism
Assembly
(Fig.
11)
When
handling
the
Pickup
Mechanism
Assembly
and
the
Unit
Mechanism
Assembly
use
a
Ground
Ring
of
the
kind
pictured
in
Fig.
11.
(A
ground
wire
can
be
made
with
ordinary
lead
wire.)
(3) Precautions During Replacement of Parts.
1)
Protective
sheets
(against
static
electricity)
are
stuck
to
the
service
parts
of
the
Unit
Mechanism.
Never
remove
these
sheets
under
any
circumstances
until
assembly
is
completed.
2)
If
high
temperature
is
applied
to
the
motor
lead
wire
terminal,
for
example
by
soldering,
this
may
cause
damage
to
the
motor.
3)
Make
sure
that
screws
are
set
in
tightly.
If
screws
are
loose,
this
may
lead
to
defective
disc
tracking
performance.
4)
When
installing
the
DC
Motor
Assembly,
(Slide
Motor)
be
careful
not
to
damage
the
worm
gear.
Such
damage
will
become
a
source
of
noise.
After
installation,
check
the
play
between
the
worm
gear
and
the
transmission
gear.
If
there
is
no
play
move
the
DC
Motor
Assembly
outward.
21.
5) The DC Motor (D2) and the Turntable are replaced in
the following manner:
(1) Lift the turntable off perpendicularly to the Unit
Plate.
When attaching the turntable, adjust the height
using the Height Adjustment Jig (Fig. 13). At this
time avoid placing undue lateral stress on the
shaft of the DC Motor (D2).
During the overhauling of the DC Motor (D2), do
not apply excessive force in the direction B. If
the C portion of the Unit Plate is deformed this
could cause eye-pattern deterioration. (Fig. 14)
(2)
(3
NOTE: Once the Turntable has been Removed, Do
Not Use It Again.
6) Lead Bar Check
If the lead bar is loose interference with the disc
tracking function may result. Therefore check to
make sure that the lead bar does not move in the
direction indicated by D. If it is found to move,
correct position of the Bar Plate (B) by bending in
direction E with pliers, then reassemble. (Fig. 15)
7) Since the Flexible P.W.B. can be cut easily make sure
not
to
use
excessive
force
when
servicing
the
Unit
Mechanism Assembly (replacing parts). Ground the
flexible P.W.B. after it is removed by clamping it
with a metal clamp or similar metal object. (Fig. 16)
Safety Devices (Fig. 17)
This
equipment
has
a
safety
device
built
in
to
the
disc
cover
which
automatically
cuts
off
laser
light
as
soon
as
the
cover
is
opened.
Be
careful
not
to
stick
pins
or
other
foreign
objects
into
this
area.
If
laser
light
comes
out
accidentally, this is very dangerous.