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ELECTRICAL MEASUREMENTS AND ADJUSTMENTS
Laser power supply
Since the light pin is very sensitive to static charges, care
should be taken that during measurements and adjust-
ments of the laser power supply the potentials of aids and
yourself equal the potential of the CD mechanism.
TO A172
BAW62
oe
TT
eal
34 530 Al2
Check
Take the flex PCB out of socket A11 and connect the
switch simulator PCB with the socket.
Remove plug A16 and insert it in the socket on the
simulator PCB.
Connect the plug with 4 wires to socket A16. Take out
plug A17 and insert the plug with 1 wire in socket A17.
The voltage should be < 15 mV.
Check of laser supply control:
Resistor 3140 clockwise (max. R):
U +v —v = 225 mV + 45 mV.
Resistor 3140 counterclockwise (min. R):
U +v —v = 750 mV + 150 mV.
Set resistor 3140 in mid-position.
Adjusting the focus bandwidth
(see service manual CD player).
Checking the AGC and offset circuit
(see service manual CD player).
Motor-control check (Hall)
1
Remove
connector AOS from the motor PCB on the
CDM.
2
Connect channel A of adual-beam oscilloscope to the
emitter of transistors 6082, 6083 and channel B to the
emitter of transistors 6084, 6085.
Position of oscilloscope: 2 V/div — 10 ms/div.
3
Connect pin 1 of connector A09 on the motor PCB to
the ground of the set.
Switch the set on.
Apply a negative voltage to pin 2 of connector AO9.
The voltage may not be applied until after the circuit
has been connected to power supply voltage. Start
from 0 V and slowly proceed to —5 V. Now the motor
should run.
When the motor runs the voltage can be brought to
approx —2.5 V. The motor should continue to run
then.
6
Theoscilloscope should display sinusoid signals now
(see Fig. A).
After approx 2 s they should lie symmetrically round
the O-axis and be shifted 90° relative to each other.
The
maximum
ratio of the amplitudes
of these 2
signals is allowed to be 1:2.
7
The amplitude depends on the applied voltage.
The V-in/V-out pp ratio should lie between 1:2 and 1:3.
8
Determine at which V-in the motor runs at 600 rpm.
At 600 rpm the frequency of V-out is 30 Hz.
At this speed V-in should lie between —1.5V and3.7V.
Conclusion:
When all these conditions are present motor and PCB
may be considered in order.
If points 5, 6 and 7 are not correct, the fault should most
probably be found in the electronics.
If points 5, 6 and 7 are correct and the voltage to be
applied at point 8 is e.g. —4.5 V to obtain a motor speed of
600 rpm, there will most probably be something wrong
mechanically. E.g. the bearing friction is too high.
V
35 181 A 20
Fig. A
ELECTRICAL MEASUREMENTS
AND ADJUSTMENTS
Laser power supply
Since the light pin is very sensitive to static charges, care
should be taken that during measurements and adjust-
ments of the laser power supply the potentials of aids and
yourself equal the potential of the CD mechanism.
7k5
470E
BAW62 BAW62
36785 Al2
Check
The laser simulator PCB nr. 4 (4822 395 30244) should be
used here.
Take the flex PCB out of socket A11 and connect the switch
simulator PCB with the socket.
Remove plug A13 and insert it in the socket on the simulator
PCB.
Connect the plug with 4 wires to socket A13. Take out plug
A14 and insert the plug with 1 wire in socket A14.
Set the switch on the simulator PCB in the OFF position and
the mains switch in the ON position.
Turn trimming resistor 3140 clockwise (max. R) and mea-
sure the voltage between points +V and —V on the simula-
tor PCB.
The voltage should be < 15 mV.
Check of laser supply control
Set the switch on the simulator PCB in the ON position and
measure the voltages between points +v and —v on the
simulator PCB.
Resistor 3140 clockwise (max. R):
U +v —v = 225 mV + 45 mV.
R3140 counterclockwise (min. R):
U +v —v = 750 mV +150 mV.
Set resistor 3140 in the mid-position.
This is a preliminary adjustment. After the simulator PCB
has been removed the laser current must be adjusted. (See
Service Manual CD player).
Adjusting the focus bandwidth
(See Service Manual CD player).
Checking the AGC and offset circuit
(See Service Manual CD player).
TO A142
3
1984-10-10
Motor-control check (Hall)
1.
Desolder the wire from point C152 on the preamplifier
printed panel on the C.D.M.
2.
Connect channel A of a dual-beam oscilloscope to the
emitter of transistors 6082, 6083 and channel B to the
emitter of transistors 6084, 6085.
Position of oscilloscope: 2 V/div — 10 ms/div.
Switch the set on.
Apply a negative voltage to the wire desoldered.
The voltage may not be applied until after the circuit has
been connected to power supply voltage. Start from 0V
and slowly proceed to —5 V. Now the motor should run.
When the motor runs the voltage can be brought to
approx. —2.5 V. The motor should continue to run then.
5. The oscilloscope should display sinusoid signals now
(see Fig. A).
After approx. 2s they should lie symmetrically round
the O-axis and be shifted 90° relative to each other.
The maximum ratio of the amplitude of these 2 signals is
allowed to be 1:2.
6. The amplitude depends on the applied voltage.
The V-in/V-out pp ratio should lie between 1:2 and 1:3.
7.
Determine at which V-in the motor runs at 600 rpm.
At 600 rpm the frequency of V-out is 30 Hz.
At this speed V-in should lie between —1.5 V and 3.7 V.
Conclusion:
When all these conditions are present motor and PCB may
be considered in order.
If points 4, 5 and 6 are not correct, the fault should most
probably be found in the electronics.
If points 4, 5 and 6 are correct and the voltage to be applied
at point 7 is e.g. —4.5 V to obtain a motor speed of 60 rpm,
there will most
probably
be something
wrong
mecha-
nically. E.g. the bearing friction is too high.
V
35 181 A 20
Fig. A
CS 98 649
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