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8. Focus Error Signai (Focus S Curve) Verification
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.
—
@ Objective
@ Symptom when out of
adjustment
Connect the oscilloscope to
Test mode, stop
TP1, Pin 6 (FCS. ERR).
@ Measurement instru-
@ Player state
ment connections
7
@ Adjustment location
| None
[Settings]
100 mV/division
Sms/division
DC mode
YEDS-7
@ Disc
[Procedure]
1, Connect TP1 Pin 5 to ground.
2, Mount the disc.
3. While watching the oscilloscope screen, press the PROGRAM 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 PROGRAM key is pressed, press this key over and over
until you have checked the waveform.
A
A=B
A+Bz25Vp-p
B
Figure 8
[Judging the pickup}
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.
{. The tracking error signa! amplitude is extremely small (less than 2 Vp-p).
2. The focus error signal amplitude is extremely smal} (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 VRI (laser power) is adjusted , the RF signal can not be
brought up to the standard level.
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