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CX-958
5) Focus and Tracking Automatic Gain Control
This function is used for implementing automatic
control of the focus and tracking loop gain.
The following is the adjustment procedure :
(1) Inject disturbance to the servo loop.
(2) Extract the error signal (FE and TE) generated at
when the disturbance is applied to obtain the
signals G1 and G2 via the B.P.F.
(3) The microcomputer reads the G1 and G2 signals via
the LSI.
(4) Based on the necessary correction calculated by the
microcomputer, the LSI performs the loop gain
adjustment.
Above adjustments are repeated several times to
ensure higher adjustment accuracy.
6) Automatic RF Level Adjustment (RFAGC)
This adjustment is used for implementing intended
signal transmission successfully by adjusting
unevenness of the RF signal (RFO) levels, that results
from disc and machine relevant factors, to a target
value. The adjustment is actually done by varying gain
of the amplifier provided between the RFI and RFO.
The following is the adjustment procedure :
(1) Using the command, the microcomputer reads the
output from the RF level detection circuit on the
servo LSI.
(2) Based on the read value, the microcomputer
calculates an amplifier gain that will produce the
target RFO level.
(3) The microcomputer sends the corresponding
command to the servo LSI so that the above gain
value may be set.
Gain of entire RFAMP
+ 12dB
+ 6dB
TYP
14
Play the CD-RW with the gain being set to +12dB
y y y y y y y
Play at +6dB increases due to stained lens or other reasons
(the typical gain is employed for the initial setup)
Fig.19 : CONCEPTUAL DIAGRAM OF PRE-AMP GAIN ADJUSTMENT
This adjustment takes place at the following timing :
• When the focus close alone is completed during the
setup process.
• Just before the setup is completed (just before the
play takes place).
• After the off-focus has been corrected during the play.
7) Adjustment of Pre-Amp Stage Gain
It is used for adjusting the entire RFAMP (FE, TE and RF
amplifiers) to +6dB or +12dB depending on given gain
level when reflected light from the disc is significantly
below the required level due to stained lens. This
phenomena can be noticed when playing back the CD-
RW.
The following is the adjustment procedure :
When reflected light from disc is judged to be
significantly below the required level during the setup,
set the entire RFAMP to +6dB or +12dB. In this case, if
the gain is modified, the setup have to be repeated
from the first step.
Through the adjustment, if you judged the play
becomes available by setting the entire RFAMP to +6dB,
+6dB should be selected for the setup next time on.
See the figure below :
Play is started with +6dB
judging the lens is stained
Time
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