Table of Contents
Advertisement
1. Focus Error Signal (Focus S Curve) Verification
@ Objective
To judge whether the pickup is ok 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 waveform for the focus error signal.
@ Symptom when out of
adjustment
@ Adjustment location
| None
(VC).
é
Shh
i
YEDS-7
[Settings]
100 mV/division
edie
5 ms/division
DC mode
[Procedure]
1. Connect TP1 Pin 3 to ground. Short-circuit the both side of C331.
2. Mount the disc.
3. While watching the oscilloscope screen, press the PROGRAM key and observe the waveform in Figure 2 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 PROGRAM key is pressed, press this key over and over
until you have checked the waveform.
A
A=B
A+B 22.5Vp-p
B
Figure 2
[Judging the pickup]
Do not judge the pickup until all the adjustment 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 VR1O1 (laser power) is adjusted , the RF signal can not be
brought up to the standard level.
38
Advertisement
Table of Contents
