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PD-41,PD-9700
8. Focus error signal(focus S curve)verification
@ Objective-
@ Symptom when out
of adjustment
To judge whether the pickup is O.K. or not by observing the focus error signal. The pickup is judged from
the amplitude of the tracking error signal (as discussed in the section on adjusting the tracking error
balance) and the wave form for the focus error signal.
aoe 2
@ Measurement instru-
ment connections
[Procedure]
Connect the oscilloscope to TP 1 Pin|
@ Player state
Test mode, stop
6 (FOCS ERR).
[Settings]
100 mV/division
@ Adjustment location | None
5 ms/division
DC mode
1. Connect TP 1 Pin 5 to ground.
2. Mount the disc.
3. While watching the oscilloscope screen, press the OUTPUT key and observe the waveform in Figure 8 for a moment.
Verify that the amplitude is at least 2.5 Vp-p and that the positive and negative amplitude are about equal. Since the
waveform is only output for a moment when the OUTPUT key is pressed, press this key over and over until you have
checked the waveform.
[Judging the pickup]
A
A=B
A+B22.5
Vp-p
B
Do not judge the pickup until all the adjustments have been made correctly. In the following cases, there may be
something wrong with the pickup.
1. The tracking error signal amplitude is extremely small (less than 2 Vp-p).
2. The focus error signal amplitude is extremely small (less than 2.5 Vp-p).
' 3. The positive and negative amplitudes of the focus error signal are extremely asymmetrical (2 : 1 ratio or more).
4. The RF signal is too small (less than 0.8 Vp-p) and even if VR 1 is adjusted (laser power), the RF signal can not be
brought up to the standard level.
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