CX-938
5) Focus and Tracking Automatic Gain ControlThis adjustment takes place at the following timing :
This function is used for implementing automaticY When the focus close alone is completed during the
control of the focus and tracking loop gain.setup process.
The following is the adjustment procedure :Y Just before the setup is completed (just before the
(1) Inject disturbance to the servo loop.play takes place).
(2) Extract the error signal (FE and TE) generated atY After the off-focus has been corrected during the play.
when the disturbance is applied to obtain the
signals G1 and G2 via the B.P.F.7) Adjustment of Pre-Amp Stage Gain
(3) The microcomputer reads the G1 and G2 signals viaIt is used for adjusting the entire RFAMP (FE, TE and RF
the LSI.amplifiers) to +6dB or +12dB depending on given gain
(4) Based on the necessary correction calculated by thelevel when reflected light from the disc is significantly
microcomputer, the LSI performs the loop gainbelow the required level due to stained lens. This
adjustment.phenomena can be noticed when playing back the CD-
Above adjustments are repeated several times toRW.
ensure higher adjustment accuracy.The following is the adjustment procedure :
When reflected light from disc is judged to be
6) Automatic RF Level Adjustment (RFAGC)significantly below the required level during the setup,
This adjustment is used for implementing intendedset the entire RFAMP to +6dB or +12dB. In this case, if
signal transmission successfully by adjustingthe gain is modified, the setup have to be repeated
unevenness of the RF signal (RFO) levels, that resultsfrom the first step.
from disc and machine relevant factors, to a targetThrough the adjustment, if you judged the play
value. The adjustment is actually done by varying gainbecomes available by setting the entire RFAMP to +6dB,
of the amplifier provided between the RFI and RFO.+6dB should be selected for the setup next time on.
The following is the adjustment procedure :
(1) Using the command, the microcomputer reads theSee the figure below :
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
Play the CD-RW with the gain being set to +12dB
+ 12dB
+ 6dB
yyyyyyy
Play is started with +6dB
judging the lens is stained
TYP
Play at +6dB increases due to stained lens or other reasonsTime
(the typical gain is employed for the initial setup)
14Fig.19 : CONCEPTUAL DIAGRAM OF PRE-AMP GAIN ADJUSTMENT |
ACEC
PIONEER
