Samsung DVD-HR753, Service Manual

Page: 121 / 132

Circuit Operating Descriptions
Samsung Electronics 13-11
13-6 IF
1) SAW FILTER
It passes only needed band of the signal that is converted to IF frequency and decrease the others band to
minimize the effect of adjacent channel.
2) RF AGC Control
Used to determine RF AGC working point in tuner.
3) VCO Tank
When VCO tank detects PLL, it makes the signal which sets a standard.
4) AFT (Auto Frequency Tuning)
AFT automatically controls the oscillator frequency in the tuner, so that it retains a constant level.
It is a quadrature detection type. The carrier, which is detected from video det is directly input to AFT.
The 90 degree delayed phase signal is input at the same time to AFT and, the results come out.
5) IF AMP
IF signal , which is selected in Saw filter, is amplified in IF amp frequency enough to be detected. The IF amp
has parallel inputs & outputs structure.
FM Det
AFT
Lim Amp
1
2
4
5
6
10
11
12
24
21
19
14
15
16
17
Video Amp
N.S.C
APC Tine
Const SW
Lock Det
IF AGC
EQ.Amp
B/W
VCD
AGC
RF AGC Amp
Pra
Amp
Mix
APC
Det
Video Det
4.5 MHz
Tunlng
AFT Tank
SIF filter
4.5MHz
SIF Trap
VCD Tank
3
4
5 6
+B
AUDIO OUT
AFT OUT VIDEO OUT
To Tuner Section
RF AGC
To Tuner Section
From
Tuner Section
a
b
c
d
SAM Filter
RF AGC Control
(IF Amp)
Fig. 13-10