Read Sharp LC-20B2E (serv.man2) Service Manual online
7
LC-13B2H/M
LC-15B2H/M
LC-20B2H/M
LC-15B2H/M
LC-20B2H/M
3-1. Tuner circuit
The tuner, whose RF circuit is composed of FET and whose local oscillation circuit, mixing circuit, IF amplifier
circuit and PLL circuit are composed of 1-chip IC, is 2-in-1 construction which has IF signal processing circuit
built in.
The channel selection circuit is of PLL frequency synthesizer type under the control of I2C bus. The receiving
frequency range is from 44.25 to 863.25 MHz, which can cover almost all VHF, UHF and CATV channels.
The IF signal processing circuit of the split carrier type employs the video PLL synchro system.
For video, a 1Vp-p composite signal is outputted from the terminal No. 19 (Video). For audio, a SIF signal is
outputted from the terminal No. 15 (SIF).
circuit and PLL circuit are composed of 1-chip IC, is 2-in-1 construction which has IF signal processing circuit
built in.
The channel selection circuit is of PLL frequency synthesizer type under the control of I2C bus. The receiving
frequency range is from 44.25 to 863.25 MHz, which can cover almost all VHF, UHF and CATV channels.
The IF signal processing circuit of the split carrier type employs the video PLL synchro system.
For video, a 1Vp-p composite signal is outputted from the terminal No. 19 (Video). For audio, a SIF signal is
outputted from the terminal No. 15 (SIF).
21
ANT
ANT
HPF
BPF RF AMP
BPF
RF AMP
T.BPF
MIX
OSC
LPF
SAW
VIF
AMP
VIDEO
DET
FM DET AF AMP
EQ
AMP
SAW
IF AMP
MIX
I
2
C PLL
OSC
MIX-PLL IC
T.BPF
VHF SECTION
AGC
1
AS
3
SCL
4
SDA
5
MB
6
BP
7
BT
9
IF OUT
11
SIF
AMP
AGC
AFT
18
MUTE
17
SIF
OUT 15
OUT 15
AUDIO
OUT 16
OUT 16
VIDEO
OUT 19
OUT 19
Fig. 3-1. Tuner circuit
VIDEO OUT signal waveform
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