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Maintenance
of
Laser
Pickup
(1) Life of the laser diode
When the life of the laser diode has expired, the
following symptoms will appear.
1. The level of RF output ( EFM output: ampli-
tude of eye pattern) will be low.
2. The drive current required by the laser diode
will be increased.
In such
a case,
check
the
life of the
laser
diode by the flowchart below
Is RF output
more than 0.8 Vp-p?
Is the laser
diode drive cerren:
than 120 mA?
less
(2) Measurement of laser diode drive current
Measure the voltage across the resistor R671 by
using a milli-voltmeter. When the voltage is more
than 1.2V, it shows that the life of the laser diode
has expired.
Front
(Parts side)
P601
=—
@y
DC MILLI-VOLTMETER
Rear
(3) Semi-fixed resistor on the APC PC board
The
semi-fized
resistor on the APC
printed
circuit
board
which
is attached
to the
pickup
is used
to
adjust the laser power. Since this adjustment should
be performed
to match
the
characteristics
of the
whole
optical
block,
do
not
touch
the
semi-fixed
resistor.
If the laser power is lower than the specified value,
the laser diode is almost worn
out, and the laser
pickup should be replaced.
If the semi-fixed resistor is adjusted while the pickup
is functioning
normally,
the
laser
pickup may
be
damaged due to excessive current.
CA-MXS 3BK
Replacement of
Laser Pickup
Before installing the pickup
Unsolder the part @, which is used for
countermeasure for static electricity.
Turn off the power switch and, disconnect the
power cord from the ac outlet.
Replace the pickup with a normal one. (Refer to
"Pickup Removal"
on the previous page)
Plug the power cord in, and turn the power on.
At this time, check that the laser emits for
about 3 seconds and the objective lens moves up
and down.
Note: Do not observe the laser beam directly.
Play a disc, and when it starts rotating, short
circuit between TP2( TEST) and GND.
Adjust tracking gain.
Adjust tracking offset .
Disconnect TP2 (TEST) from GND.
Check the eye-pattern at TP3(RF)
Finish.
Note: Since one adjustment may affect other settings,
repeat these adjustments a few times.
(No, 20373)
1-55
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