Kenwood DP-3010 Service Manual page 13

DP-3010
CIRCUIT DESCRIPTION
5-4. Operation Information
e RF AMP
The 1/4 pin photodiode output for the Main Beam Detec-
tion of the Pick-up Three-Beam Optical Method is shown
in Diagram 5-1. Pins FS1 and FS2 of TA8101N are directly
connected to the above output so that (B+D) and (A+C)
signals are input here. The (B+D) and (A+C) signals are
converted from current to voltage in Converter 1a and 1b
(I—V). The summed signal (A+B+C+D) passes through
the RF AMP and is output from the RFO pin. Since the pin
photodiode is an equalized constant voltage supply. the
curcuit is designed so that the insertion loss of the gain to
Direction of current flow
30K
Converter 1b (I—V)
the RFO output will be typically 81 kQ (R2, C1 excluded)
when the external feedback resister (VR1+R1) of the RF
AMP is 27 kQ.
The insertion loss for FS1 or FS2 to RFO is calculated as
follows:
RT (RF) = 3RNFI = 3 X27k0N = 81k
RF Signal
(A+B+C+0)
Diagram 5-1 RF AMP Construction
DP-3010
CIRCUIT DESCRIPTION
© Focus Error AMP
The signal difference {(A+C) — (B+D)} between Converter
1a (1—V) and Converter 1b (I—V) is output from the FEO
pin after passing through the Focus Error AMP.
The circuit is designed so that the gain from the Converter
(I—V} to FEO will have a typical insertion loss of 123 kN.
(external resistance is RNF2 = VR2 = VR3 = VR4 = 82
kQ).
The output from the FEI attenuator is adjusted for focus
gain in TC9201BF. From the two analog switches, FEL1
and FEL2, it is attenuated to about 0.8 Vp-p. the Pick-up
dispersion is corrected and then it is input to the Focus
Servo AMP.
Converter 1b (I—V}
VREF
VR2 is used as the balancer for the Focus Error Signal
where the offset is adjusted.
The insertion loss for FS1 or FS2 to FEO is calculated as fol-
lows:
RT (FE) = 1.5 RNF2 = 1.5 X82k0 = 123k
TC9201 BF
Focus Error AMP (FE)
Diagram 5-2 Focus Error AMP Construction
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