Harman Kardon FL8385 Service Manual page 18

FL8385
RF, EQ, AGC
C47
36
35
34
33
The signals A, B, C and D input from PDIC are composed into the RF signal by the RF
Addition Amp, then output from RFOUT of Pin 5. This Amp is designed so that RFOUT is
about 0.5 Vp-p for normal CD disc (about 0.4 Vp-p for CDR and 0.12 Vp-p for CDRW).
RF signal from Pin 5 is then input to the AGC block through the EQ block (the EQ
characteristic is fixed for single speed operation in this design). It is then gain-controlled
and output to Pin 10 ARF. The AGC block maintains the output level of ARF to about
1.0Vp-p for all types of disc. C38 connected to Pin 9 is for the AGC loop filter.
The RF Detection block detects the amplitude of the RF signal inputted from the EQ block.
Inputted RF signal is detected after passing through a high-pass filter. Detection level is
changed in accrodance with the voltage of GCTRL Pin 28.
The ENV detection block detects the fluctuation of the 3T-composition in the RF signal
which is needed for focus balance adjustment. C39 connected to Pin 11 forms a filter for
detecting the signal fluctuation. The ENV output signal from Pin 12 is filtered by C29.
R27
R21
R20
C28
C35 RFOUT
3 5 6
EQ
GCTRL
ARF
NRFDET
V V
CC1 CC1
C39
C38
8 9 10 17 11
AGC
DETECTION
RF
DETECTION
18
harman/kardon
ENV
C29
12
ENV
C2
28
V
GCTRL
FL8380