Pioneer PR-8210-A Service Manual page 25

in activation of the Z405 PFC (phase-frequency
comparator), and the generation of a pulse signal at
pin 10 of Z405 in proportion to the phase differ-
ence between REF H and PB Н. This pulse signal is
passed through a low-pass filter and amplified by
AMP1. This output is also amplified by AMP2 and
used to control motor speed.
4-b Stopping
When the REJ key is pressed, RUN is switched
from L to H level, resulting in S8 being turned on,
and the AMP2 output being switched to —0.5V.
This output is amplified, and by making the motor
terminal voltage negative, effectively brakes the
motor. Once the disc rpm drops to 360, СОМР1 is
inverted, resulting in pin 6 being reduced to —Vcc.
Q423 is thus turned on and the brake released.
4-c Gain control
15v
12v
TACH O3V}----
ом
55
PR-8210-A
4-d Motor servo during focus unlock mode
4-e Disc size detector
The 8 in. and 12 in. disc diameters are detected
by COMP6. A voltage proportional to the motor
rpm is applied to one of the comparator inputs,
while a voltage which detects the motor current is
applied to the other, thereby ensuring that disc size
is properly determined with both CAV and CLV
discs alike.
$7
58
59
$3
9420
Fig. 22 UM3002 timing chart
25