Maintenance Of Laser Pickup; Adjustment Procedures - Jvc Xl-V200B Service Manual

XL-V200B XL-V200B |
12. Maintainance of Laser Pickup
12-(1) Service life of the laser diode
1. Connect the IC301 pin 22 of Front PCB (ENN-
020-2) to GND, and turn the power switch ON. Then
measure the laser radiation power with the laser
power meter, If the indication is obtained less than
0.35mW, then the service life of the laser diode should
be judged as having expired.
2. When the EFM output is extremely low, that cannot
focus enough, the service life of.the laser diode
should be judged as having expired.
12-(2) Replacement of the pickup and procedure of adjust-
ment
1. Remove the old pickup from the pickup base as-
sembly with loosing three screws, and disconnect two
connectors.
Pickup replacement
Adjustment of laser power
Operate with a disc loaded.
No reading of TOC
NO
Observe RF eye pattern. Signal from TP10
Adjust the axis of the Loosem the fixing screw
spindle motor, beforehand.
: YES
2nd adjustment
NO
Turn OFF the tracking
Shortcircuit TP2 and
servo, Ground.
Adjust grating to obtain
the maximum tracking
error signal.
Signal from TP1
Set R234 (Tracking Offset
VR) as the tracking error
signal involve no DC offset.
Turn ON the tracking servo.
ment.
Observing RF eye pattern,
perform electrical adjust-
1. Adjust Focus Offset.
2. Adjust Mirror Offset.
2. Take out a new pickup from the package, and con-
nect two connectors.
3. To replace the pickup, turn the adjustment screw so
that its protruding section faces the left-hand side
(pickup side) as shown in the figure below. Also, if a
spacer is inserted, remove this spacer because it is not
necessary.
Adjustment
Screw
Pickup
Pickup Base
4. Attach it to the pickup base with three screws.
5. Don't touch the objective lens surface in these proce-
dure.
6. Adjust grating referring to the adjustment procedure.
Note: Every semi-fixed VR should be set at its center position.
Turn OFF the Tracki
Note:
Adjust several times by re-
peating starting operation.
lear tracking
error signal can be
observed,
Adjust grating by turning
it 90° clockwise,
Set R234 (Tracking Offset
VR) as the tracking error
signal involve no DC offset.
YES
Adjust grating by turning
it 90° counterclockwise.
Turn ON the tracking servo. |
Note:
Every offset position is at
the center or within 3 de-
grees right-/left-ward.
Adjust the Trackin
ee pee ee
(No. 2847) 1-16
13. Adjustment Procedures
13-(1) PLL freerun adjustment
1) Adjustment instrument
Frequency counter
2) Adjusting procedure
1. Connect the frequency counter between ENN-020
TP 41) and GND.
2. Short the TP 40) and GND.
3. Adjust the L601 to 4.322+0.001 MHz indicated on
the frequency counter with the regulating rod.
4. Perform this checking no sooner than switching on
the power.
13-(2) Grating adjustment
1) Adjustment instruments
Oscilloscope, Normal disc
2) Adjusting procedure
1. Connect the oscilloscope between ENN-020 TP (1)
and GND.
2. Play the disc.
3. Play the disc until 1/3 of the program area is played.
(15 minutes in passing time at 34 mm radius)
4. Short the TP 13° to GND, and TP @) to GND simul-
taneously.
5. Drive the grating adjustment screw of the laser pick-
up, and find the point where the tracking error signal
(waveform on the oscilloscope) becames maximum
amplitude, and then fix it.
6. Return the pickup to the inner track and make sure
that the amplitude is no change.
7. Advance the pickup to the outer track and make sure
that the amplitude is no change.
Grating adjustment screw
Note: After shorting the TP (3) to GND, it will be ir-
regular indication on FL. display. This phenomena
has no problem with these adjustment.
In the case of it can't recover to the normalcy
after disconnect two wires that are shorting the
TP (3) to GND and TP (2) to GND, it can re-
start by Power SW.
1-17 (No. 2847)
13-(3) Y Axis adjustment
1) Adjustment instrument
Oscilloscope, Hexagonal wrench (2 mm), Normal disc
2) Adjustment procedure
1. Connect the oscilloscope between ENN-020 TP 40)
and GND,
2. Play the disc.
3. Drive the Y axis adjustment screw under the pickup
base, and find the point where the RF signal (wave-
form on the oscilloscope) becomes maximum ampli-
tude and the finest waveform.
4. This adjustment performs inner area of the disc.
5. Advance the pickup to the outer track and make sure
that the amplitude doesn't come down 2/3 below of
inner track,
Y axis adjustment screw
TO
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020-NN4
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TP)
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XL-V200B