Pioneer PL-200 Service Manual page 16

7.3
OPERATION OF THE PDlOO3
IC
(OSCILLATOR
STAGE)
1. Once
the power supply is turned on, the
quartz
crystal oscillator
generates
a 6744kHz
signal.
2.
The
frequency
of
this
signal
is
reduced to
1.5kHz (714096 division) by frequency divider
I.
Part
of
the
resultant
signal
is
passed
via
the
x'tali
RC
switching
circuit and
applied
to
frequency divider
II.
The other
part
of
the
signal
is applied
to
frequency divider selector
II.
3.
The 1.5kHz signai applied
to
frequency divider
II
is further
divided
into
a
750H2 signal,
and
applied
to
frequency divider selector
I
where
the
signals are converted
into
sampling pulses
for
phase
comparison purposes
in
PA2004.
33rpm
27.78H2
45rpm
37.5H2
(In both
cases,
the
pulse
width
is 0.66?ms).
4. Frequency divider selector
II
converts
signals
from
frequency divider
I
into
pulse signals for
the
stroboscope lamp drive circuit.
33rpm
55.5H2
45rpm
71.OHz
(In both
cases,
the pulse width
is again
0.667ms).
NOTE:
This
IC
(PD1003) is not
employed
in
the motor of
the
PL-200
and
PL-225
models.
7.4
OPERATION OF THE
PA2OO4
IC
(coMPARATOR
CONTROL)
1. Signals
from the
frequency generator
in
the
motor rotation
ass'y are changed into
50%
duty
square wave signals
by
the waveform rectifier.
The frequencies at this
stage
are
thus,
33rpm
55.55H2
45rpm
75Hz
2.
Part
of
the output is
divided by
Vz
in
the
FF
circuit, and
subsequently applied
to
the
FV
converter
circuit
along
with
the other part of
the output formed
in
step
1
above, thereby
forming
the FV
converter gate pulse
sigaals.
3. The
output from the FV
converter
is
applied to
buffer amplifiers
I
and II.
4.
The buffer amplifier
I
output
is compared with
the
reference voltage
in
buffer amplifier
III,
and
then applied
to
the output
compose circuit.
5. Phase
comparison
of
the
sampling pulses from
the
PD1003
IC with the FV
converter output
occurs
in
buffer amplifier
II,
with
the resultant
output
being applied
to
buffer amplifier
IV.
6.
The output from buffer
amplifier
IV
is
also
applied
to
the output
compose circuit.
7.
This
output
compose
circuit
consists
of
a
low-
pass
filter
(cut-off frequency
23H2,
cut-off
slope
-6dB/oct.)
which
serves
to
eliminate the carrier
component
in
the output of buffer
amplifier
II
(phase comparison).
8.
This
final output
signal
is then
passed
onto
the
comparator
control
stage
of
the PA2005 IC for
comparison
with
the
reference voltage.