Advertisement
Adjusting the focus bandwidth
Make a measurement setup according to the figure.
Play from test CD 4822 397 30096 track 1 (CD without defects).
Adjust with resistor 3158 to PRE-AMPLIFIER. + LASER PCB the
phase difference between the signals A and B decreases to 180°.
This corresponds to a minimum distance D on the Lissajous figure.
R=47kΩ -1%
5322 116 54671
C=10nF -1%
5322 121 54154
Laser power supply (NEG.VOLT.PH.)
Since the light pen is very sensitive to static charges, when
measuring and adjusting the laser power, the tools and
yourself must have the same potential as the CD
mechanism.
Control
The laser simulator board 4822 395 30203 must be used for this.
Remove the flex board from connector A11 and connect the
simulator board to the connector.
Remove plug A16 and insert it into the connector on the simulator
board. Connect the 4-wire plug to connector A16.
Disconnect plug A17 and insert the 1-wire plug into connector A17.
In the quiescent state, the current through the laser diode should be
≤ 1mA.
Control:
Set the switch on the simulator board to the "OFF" position and the
power switch to the "ON" position
Turn bias resistor 3180 counterclockwise (min. R) and measure
voltage across resistor 3194.
The voltage measured should be ≤ 10 mV.
Checking the control of the laser power supply:
Set the switch on the simulator board to the "ON" position and
measure the voltages between point V and ground on the simulator
board.
Resistance 3180 clockwise (max. R):
Uv to ground = -120 mV ± 24mV.
Resistance 3180 counterclockwise (min. R):
Uv to ground = -720 mV ± 144mV.
Set resistor 3180 so that Uv to ground is ≈ -500 mV.
This is a preset. After the simulator PCB has been removed, the
laser current must be set.
Adjust
Play from test CD 4822 397 30096 track 1 (CD without defects).
Connect across resistor 3308 to SERVO PCB a DC voltmeter.
Use resistor 3180 to adjust the laser power supply so that the voltage
across resistor 3308 is 500mV ± 50mV.
Note
A laser current that is too high (> 550 mV across resistor 3308)
shortens the life of the laser diode.
Advertisement
