Motor Operation Point Adjustment; Buffer Amplifier - Pioneer PL-88F Service Manual

9.9 MOTOR OPERATION POINT ADJUSTMENT
1. Open the slide base as described in "Dummy
Play Mode Setting", and run the motor at 33-1/
3rpm.
2. Connect the buffer amplifier shown in Fig.9.14
to the 3P connector from the motor base plate,
and connect the output
to a oscilloscope
(making the lead wire length less than 10cm to
reduce the effects of extraneous electrical noise).
3. With a waveform like that shown in Fig. 9.15 in
the synchroscope, vary the gain to adjust the
peak-to-peak distance in the sawtooth waveform
to five divisions.
4. Then adjust VRl to obtain an a:b ratio of 3:2 in
Frg. 9.15 (taking every precaution to eliminate
unwanted noise).
5. After completing the 33-U3rpm
adjustment,
repeat the process for 45rpm. Always adjust the
33-U3rpm speed before the 45rpm speed. And
even if only the 33-U3 rpm speed initially needs
adjustment, also adjust the 45rpm speed after
the 33-1/3rpm adjustment. Adjust VR2 for
45rpm. After completing the 45rpm adjustment,
check the 33-1/3rpm speed.
Slide base cover
Fig. 9-13 Motor Operation Point Adjustment
F i g . 9 . 1 4 B u f f e r A m p l i f i e r
Motor
3P connect
I S m s e c ( 3 3 )
l 3 . 3 m s e c ( 4 5 )
Fig. 9.15 Adjustment Waveform
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t \
, lli
\ry
0 l
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I I
t o t \
A I
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F i g . 9 . 1 6 A d j u s t m e n t P o i n t
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