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8. FCS SERVO LOOP GAIN ADJUSTMENT
{Mechanical Adjustment]
e Purpose:
Setting the FCS servo's loop gain to the optimum setting.
@ Symptom when incorrectly adjusted:
Playability is poor.
Measurement equipment
Measurement equipment
Player condition
Adjusting points
& jigs
connecting points
@ Oscilloscope
® Oscilloscope
@ Test mode
@ VR604
®@ Test disc (GGV1003)
CH 1(X):
-STILL mode
@ AF oscillator
Between FCS IN
*TRK servo loop close
(1.7 kHz/10 Vp-p)
(CN301-6) and GND.
'TILT servo ON
@ Resistor (47 k ohm)
CH 2(Y):
FCS error (CN301-5)
Adjusting procedure
1. Search for frame #15000 on the test disc.
2. Connect CN301-5 and CN301-6 as shown below.
3. Set the oscilloscope to the X-Y mode and look at the
resurge waveform.
4, Adjust
VR604
so
that
the
resurge
waveform
is
symmetric
with respect
to the X and
Y axes.
(See
Photos 1 and 2.)
Adjustment diagram
Mother Board Assembly
Oscilloscope
AF Oscillator
1.7KH27
i0Vp~p
17
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