Samsung DVD-HR755, Service Manual

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Circuit Operating Descriptions
13-10 Samsung Electronics
13-5 Tuner
1) Low Pass Filter & High Pass Filter
This consists of IF trap circuit and UHF & VHF separation circuit. If the input signal is IF (45.75MHz),
this filter
prevents interference.
2) Single tune
This consists of a filter circuit, RF AMF, impedance conversion circuit, image trap and a single tuning circuit. It
prevents noise and other interference signals. It is very important part which improves NF (noise figure) and
prevents the various of spurious signals.
3) RF AMF
RF AMF is made of FET (Field Effects Transistor). It is controlled by AGC coming from IF DEMOD block.
4) Double tune
It consists of a double tuning circuit to improve characteristic of rejection that results in a better band
characteristic.
5) Mixer IC (Mixer, OSC, PLL)
It consists a VHF and UHF OSC and Mixer circuit. We applied mixer to make better characteristic of rejection,
it shows especially various beat characteristic.
6) PLL IC
The PLL IC plays a role selection of Tuner channel. It was built-in three wire PLL IC, charge pump and band
driver.
The minimum of step frequency is 31.25KH z.
<
<
>
>
Fran
Modulafor
b a
c
d
e
VHF
8.P.F
VHF
SingleTune
VHF
RF Amp
VHF
Double Tune
Mixer
IF Amp
OSC 8uffer
VHF OSC
IF Single
IF
< >
+B
1/8 Prescaler Band Driver
Prog.Dirlder
Phese Code
Charge Pump
Band Driver
3wice Bas
Recelver
VHF
Single Tune
VHF
-RF Amp
VHF
Double Tune
VHF Mixer
VHF OSC
VHF
OSC Amp
~
VHF OCS
L.P.F
~
~
~
AGC
10
9 8 6
15 X-tal
4MHz
1
* ( )
1
4
3
2
1
^
&
16
14 13 12
V
L
V
H
U
Fram IF Sectlon
Fram IF Sect lon
TO IF Sect lon
PB TU
CLOCK DATA ENABLE
LOCK
3 5
12
1
7 8
9
Mix IC IC100
f PLL IC
Fig.13-9