Circuit Descriptions - Harman Kardon FL8550 Service Manual

Circuit Description
1. RF AMP BLOCK
The KA9220 is designed for 3-spot type optical pick-up assembly. The photo detector is composed of 6
light sensor (A through F). The photo detector A, B, C and D detect audio modulation signal on the disc
and generate focus error signal.
RF I-V AMP (1) and RF I-V AMP (2) are converted current of PD1 (A + C) and PD2 (B + D) through the
58 Kohm Internal resistor into Voltage.
Furthermore, they are added to RF Summing amplifier.
This signal (A + B + C + D) is outputted from RFO (Pin66).
The output Voltage is as follow.
V R3 X ( iPD1
= −
RFO
V
R3 X (
= − A +
R1
V
- 22K X ( A
=
10K
- 2.2 X ( V
= +
A
iPD2 )
+
V
)
B
R2
V
B )
+
10K
V )
B
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FL8550