Pioneer LD-V4300D Service Manual page 87

12.TRACKING SERVO LOOP GAIN ADJUSTMENT
• Purpose: To set the loop gain of the TRKG (tracking) servo to the optimum value.
• Symptoms when incorrectly adjusted: Play ability grow worse.
Measurement equipment
& jigs
Measurement equipment
connecting points
• Oscilloscope
• Test disc: GGV1003
• Oscilloscope: In FTSB
assembly
CHl
(X): Between
TPl-7 (TRKG ERR
IN) with lO0kO and
GND
• AF oscillator
•
Resistance (l00kO)
CH2
(Y):
TPl - 9
(TRKG ERR OUT)
Adjusting procedure
I. Play the test disc and search for frame
#
15,000.
2.
Connect the
X
and
Y
terminals of the oscilloscope as
shown in Fig. 12-1, and observe the Lissajous's
waveforms.
3. Adjust VR3 so that the Lissajous's waveform as
shown in Photo 15 appears. Photo 14 shows a
waveform when the adjustment is incorrect.
Adjustment diagram
118
Oscilloscope
100kS2
0
, - - - - - - ,
FTSB
assembly
H1(X
~ - - - - - - - - t - - - - +-<JCH2(Y
•~
D 0
@
0
0
oo
0
~
Fig .
12-1
0
AF
oscillator
3.3kHz/10Vp-p
Player condition Adjusting points
*
Normal mode: • VR3 in the FTSB assembly
• Still mode
• TILT servo OFF
Waveforms
• Oscilloscope range:
X-Y
mode
X:
0.2mV/div.
DC
input
Y :
10mV/div.
DC
input
Waveform when insufficiently adjusted
D