Pioneer DR-R504X Service Manual page 25

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DR- R504X
[How to find the null point]
When you insert the small screwdriver into the slit for the grating adjustment and change the grating angle, the
amplitude of the tracking error signal at TP201 (CN601), Pin 2 changes. Within the range for the grating, there are
five or six locations where the amplitude of the wave reaches a minimum. Of
t~ese
five or six locations, there is only
one at which the envelope of the waveform is smooth. This location is where the three laser beams divided by the
grating are all right above the same track. (See Fig. 6.)
This point is called the null point. When adjusting the grating, this null point is found and used as the reference
position.
Turning the grating counterclockwise
••--11----
0
Turning the grating clockwise
~~~
m
t
i ·
~
1 J
m
~~~
0 0 0 0 0 0 0
~1~1~1~1M
/
~II
point
Waveform of
TP201 (CN601 ), Pin 2
Graing adjustment position
Null point waveform
Fig. 6
Maximum amplitude
waveform
Note : If the difference between the amplitude of the error signal at the
innermost edge and outermost edge of the disc is more than 10%,
adjust the grating again.
Waveform other than the
null point
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