Service manual

CB-9
IF Receiver
Introduction
The CB chassis utilizes two tuners in order to provide PiP without requiring a second external source. This
is with the provision that the receivers antenna input is receiving multi-channel input. For example, a cable
decoder box usually only provides a single channel input. Although the television possesses two tuners,
each is receiving an identical single channel, so a second external source would have to be used here if the
user desires his PiP to be different from the main screen. On the other hand, a standard cable input or even
a regular antenna provides multiple channels that each tuner can demodulate individually.
The IF (intermediate frequency) section can be broken up into a half for each tuner. Those part designa-
tions numbered from 1200 through 1249 relate to the primary tuner, WT1200. Part designations from
1250 to 1289 apply to the secondary tuner, WT1250.
Tuner
For the most part, each tuner is fairly identical to the other as it relates to the rest of the chassis. Each
corresponds respectively to IF IC1200 and IC1250 (IFPs or IF processors), which are also identical. IF
1
2
3
4
5
6
7
8
9
10
11
12 13
14
15
16
17
18
19
20
21
22
23
24
DET-OUT SIF-IN2
1ST-SIF-AGCFM-DET
IF-AGC2 SIF-OUT
RF-AGC-ADJ VIDEO-OUT2
IF-IN1 EQ-FILTER
GND
EQ-INIF-IN2
APC-FILTER
SIF-IN1 VIDEO-OUT1
VCC VCO2
RF-AGC-OUT VCO1
AFT1 AFT-OUT
AFT2 IF-AGC1
IC1200
R1218M
C1208
TP1206
C1210M
R1208M
R1207M
+9VSW
C1209
R1206
C1211M
L1202
VCO
R1211M
C1212M
R1212M
C1213
TP1207
L1203
U1201
R1209M
R1210M
C1214M
R1216M
Q1200
C1215M
U1202
R1219M
PROV
R1226M R1225M
W1200
PROV
+9VSW
R1214
R1213M
R1222M
R1217M
CR1200
L1204
C1214C1222M
R1288M
C1219M
C1220M
R1223M
R1224M
1
2
3
45
6
7
8
U1200
C1201M
C1205M
+9VSW
C1203M
C1204
C1221M
PROV
R1202
C1200M
R1203M
R1201M
L1200
C1290
C1202M
C1207M
L1201
AFC
C1206M
R1204
R1205M
+5VTune
+33VSW
TP1200
ZD1230
C1230
C1231M
C1232
C1233M
J1201M
C1234
PROV
C1235M
PROV
TP1201
C1236
C1238M
PROV
C1237M
PROV
R1230M
R1231M
SDA
SCL
Q1290
Q1293
Q1291
Q1292
R1297M
Audio-Swap
R1298M
+9VSW
R1299
PROV
C1294
PROV
R1291M
R1293M
R1292M
R1290M
Comp-Aud
R1294M
C1292
Comp-Aud2
R1296M
C1293M
R1289M
R1295M
Q1241
Q1240
+5VSB
AFC-Main
C1240
R1240M
C1241M
R1242M
R1241M
C1242
R1246M
C1244M
R1245M
C1243M
R1244M
R1243M
Luma-SD
SD-Main
+9VSB
+9VFil
L2901
C2935
C2936M
TP1205
TP1202
AGC
Delay
Antenna
Input
To 2nd
Tuner
To Main
Tuner
Splitter
IF-Video
Main
Main Tuner
11
10
9
8
7
6
5
4
3
2
1
WT1200
SCL
Main
-
Tuner
<<Figure CB-9>>