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4-2
On the display appears "3".
(Dependent on the length of the lead-in track music will
be reproduced after approx. 1 min.).
In this state it is possible to move the arm by means of
the SEARCH FORW and the SEARCH REV keys to the
outside and to the inside resp. Now the motion is
controlled by the µP and the arm moves by steps of'64
tracks as long as the key is depressed.
If
the laser is disturbed in position "3" (as a result of
braking or removal of the disk) the player will jump
back to position
"O".
This also holds good if position
"1 • and "2" Is disturbed and position "3" is called.
The servicing programme can be left by switching the
mains switch (POWER ON/OFF) off and on (hardware
reset).
Specification measurement
l
CD PLAYER
- - - - - ; FILTER
R
Fig. 4
~NANO
DISTORTION
METER
o.g. SOVNO TECMNOLDGY
ST 17008
30
,sg
All
To measure the specification use can be made of audio
test disc 4822 397 30095.
Use 13th order filter 4822 395 30204 to measure (see
Fig.4):
- Total harmonic distortion (THD)
- Intermodulation distortion
- Signal-to-noise ratio (S/N)
Continuous burning of the laser
- Bridge c!!Q_acitor 2583 on the decoding panel.
- Connect Si (= pin 20 of 6525 on the servo
+
preampi.
panel) to ground.
- Switch on the supply voltage.
- Now the laser will burn continuously.
Note:
Danger
Invisible laser radiation.
Avoid direct exposure to beam.
Check of the laser supply
The laser and, the laser supply in IC6525 plus the
monitor diode from a feedback system.
A defect in the laser supply can result in the destruction
of the laser.
If, in that case, the laser
(=
complete CDM2 unit) is
replaced, the new laser will also become defective.
However, it is impossible to check and repair a feedback
system if a link is missing. For this reason the laser
supply can be checked with the circuit below. The green
LED replaces the laser, the voltage across the 18 Ohm
resistor is feed back as monitor voltage, the
33
Ohm
resistor and the switch serve to draw more current from
the laser supply.
CS 9 939
GB
~ - - - - - - - - - , . . . to LO
LED GREEN e.g. CQY 94 IV
CONNECTED
DIRECTLY
TO PANEL
42 444 A12
5322
130
32182
The above circuit is connected to connector 31 via an
extension cable instead of a flex print. The normal flex
print is not suited for this purpose because of its high
internal resistance.
Code no. extension cable 4822 322 40066
- Take the above flex print out of connector 31 on the
PCB.
- Connect the circuit via the extension cable to the
connector.
- Select the play mode by grounding Si (pin 20 of IC6525).
Note: Si=
0,
start initialisation low, is the play mode.
- Measure the voltage LO (Laser Out) at test point 9.
SK
open:
1,8 V,,;;; LO,,;;;
2,3
V
170 Mv .,,,:; LM .,,,:; 220 mV
The green LED emits little light.
SK closed:
1
,8
V .,,,:; LO .,,,:; 2,3
V
170 Mv ,,;;; LM ,,;;; 220 mV
The green LED emits little light.
- During the change over from
SK
closed to SK open,
the LED will emit more light for a short moment.
- The control sees to It that the same amount of current
flows through the LED when SK is open and when SK
is closed.
At
si =
1,
in the STAND-BY state, LO= 0 V
±
0,2 V.
Repair procedure
Since laser, monitor diode and photodiodes are very
sensitive to static charges, care should be taken that
during measurements and adjustments the aids and
yourself have a potentlal that Is equal to that of the CD
mechanism.
Attention: When exchanging the CDM2 unit, the laser
output potentiometer 3528 should be placed in
mechanical mid-position to avoid damage to the laser.
Adjusting the laser current
Coarse adjustment
- Place potentiometer 3528 approximately in
mid-position.
- Put test disc 5 on the turntable.
- Bring the player in service position 1.
- The focusing motor can now start focusing 16x and
when it has found the focal point a "1" will appear on
the display.
- If this does not happen, turn potentiometer 3528
clockwise or anti-clockwise a little.
Here after the fine adjustment of the laser current has
to be carried out.
Fine adjustment
- Play track 1 of the test disc 5.
- Adjust potentiometer for a voltage across 3508 test
point 1 and 2 of 50 mV
±
5 mV.
(
0
(
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