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HITACHI
DA-600
m Checking the object lens (Fig. 13)
Utmost
care
should
be exercised
not to get dirt
or dust on the object lens of the lens actuator.
However,
the object
lens may
be smeared
with
dirt or dust after a long time of use.
Clean the lens
surface with a clean application.
mw Checking the laser unit
The laser unit is normally driven with a current of
40 - 70 mA.
Measure
this
laser
driving
current
value
in the
circuit.
If it is over 100 mA, the laser unit may be
defective.
(Measure the current value on the base of
the voltage (0.48 — 0.84V) across R623 (12 ohms.)
= Precautions on repair service
1. Semiconductor laser (Fig. 14)
The
semiconductor
laser requires
more
atten-
tion to electrostatic breakdown
or surge Current.
Be very careful
not to touch
the terminals
of
the semiconductor
laser and those of the flex-
ible P.W.B. by hand or with a tool.
The current — light intensity characteristic became
sharp
abruptly
after
passing
the
threshold
value as shown in Fig. 14.
The threshold current
laser
unit.
value
is a
little
different
in each
PD P.W.B.
PD Schaltplatte
Plaquette Cl PD
Loading mechaism
Lademechanismus
Mécanisme
de
charge
Connector
Stecker
Connecteur
Therefore, when
setting the laser beam amount
after replacing the unit mechanism,
be sure to
turn
the
control
variable
resistor
R629
fully
counterclockwise
to set it off once,
and
then
increase the level to the specified value.
2. Precaution in replacing parts.
(1) Protective sheets are stuck to the service parts
of the unit mechanism.
Never remove
these
sheets
prior to the completion
of assembly.
(2) If the lead terminals of the slide motor are over-
heated ed due to soldering etc., it may cause
a fault in the slide motor.
Therefore,
be sure
to unsolder the leads on the P.W.B. side during
replacement.
mg Checking the actuator
Check the resistance values of the actuator coils.
They are normal
if the resistance values meet the
following values.
Focus coil : 20 ohms
Tracking coil : 4 ohms
If any coil is open or short circuited, the actuator
may
be defective.
with
a_ tester,
moves a little.
When
the coils are checked
it can
be observed
that the lens
PX P.W.B.
PX Schaltplatte
a [| Plaquette Cl PX
RM P.W.B.
RM
Schaltplatte
Claw of tray
Klaue der Schublade
Cliquet du plateau
Rail
Plaquette Cl RM
@
Schiene
t
Glissiare
Tray
©
roieenon
Schublade
nge
Projection
Plateau
7
©
Fig. 3
Fig. 4
Abb. 3
Abb. 4
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