RÄ/ox C221 CD Player
Service
Manual
The
power
supply
produces
the following DC
voltages:
o
+5 V,
-5
V, +1 2 V,
-12
Y
,
+5
V STBY
-
stabilized
.
+20 V
(V
PYRAMIDE)- unstabilized
4.1.2
Focus control-
photo
diode signal
processor
The
photo
diode
signal
processor
lC
9 and
the
associated
components control
the
focus
control circuit.
lC 9 evaluates
the signals of the four
photo
diodes
(D1...D4)
and
the HF signal of
the laser
(HFIN).
lC
9
then
supplies
result of this
evaluation
in the form of
the two
signals Focus Error
(FE)
and
Trackloss
(TL).
The focus voltage
(Ufocus)
can be
measured
on
test
point
P31 to
ground
and adjusted
with the
potentiometer
RA3'1.
{r-
Refer to Section 5.3.1
"Adjusting
the focus voltage".
ln addition to these signals lC 9 supplies the radial
error
signals
RE(F)I and
RE(F)2 to the radial
processor
lC 10.
The laser current can
be
adjusted with the
potentiometer
RA2.
{-
Refer to
Section
5.3.2
"Adjusting
the laser current".
4.1.3 Radial control- radial
processor
The radial
processor
lC10
and
the
associated components
control the radial control circuit.
lC10
evaluates
the radial
error
signals RE1 and RE2 of lC9 as well
as
the
current intensity
(four
bits, 80...83)
supplied by the
servo
processor
lC3.
The
op-amp lC4
(7,8,1)
amplifies the
RAOUT
signal output by
lC10 and controls the radial
arm.
4.1.4 Motor
speed control
-
demodulator
The demodulator lC8 and the RAM
lC5 as well as the
corresponding components
control the motor
control circuit.
lC8 compares the actual speed
of the disc motor with the
nominal
speed of
480 RPMs
(inside)
180 RPMs
(outside).
lf the
actual and
the nominal
speed coincide, lC8
supplies
the MSC
output signal with a
pulse
duty factor
of
1:1
-
pulse
rate
=
88
kHz.
The MSC
signal-
amplified
by lC7
-
controls the disc motor.
lf
the
actual speed drops below the nominal
speed,
lC8
changes
the
pulse
duty
factor of the
MSC signal to > 1:1. ln response the
disc motor
increases its
speed. lf the actual
speed
is
greater
than
30
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