56
12. RA-4 Video Circuit Troubleshooting
N
N
3
5
6
1
2
4
63
62
64
60
59
61
32
31
56
58
52
54
53
49
42
40
38
45
47
34
35
36
25
29
7
12
13
18
19
24
A BOARD
4
1
C697
C698
D524
D525
R876
R875
J505
3
4
V
D550
R862
C706
R891
L
R892
R
R870
DET
OUT 2
Q506
L OUT
C685
R OUT
C690
TU501
MAIN
TUNER
BTF - WA
411
DET
OUT 2
+9V
Q526
TU501
SUB
TUNER
BTF - WA
411
L OUT
R OUT
C688
C687
R907
D532
C707
C708
D543
+9V
R510
C689
R554
R560
P
Q517
R804
R814
R607
C686 R794
R664
R682
P
Q518
R790
R799
FROM
IC1008
MAIN CPU
R821
Y1
R823
C1
+9V
R843
SSW1
R824
V1
R819
R820
L1
D537
R822
R1
R808
TV V
MAIN
TV
L MAIN
TV R MAIN
TV V SUB
TV L SUB
TV R SUB
SDA
SCL
MAIN
Y
C
L
R
V OUT
Y IN
SUB V OUT
SUB C IN
IC515
AVU SWITCH
CXA1845Q
SUB Y IN
SUB Y OUT
SUB C OUT
Q533
R759
N
C673
R755
R736
+9V
N
C643
L523
C639
R745
TO IC1302/28
VIDEO 3 J506
VIDEO 4 J507
VIDEO 5 J508
TO BUFFER Q532
TO BUFFER Q536
TO CN512/1
TO CN512/3
TO K
BOARD
+9V
R720
R816
CM501
VIDEO
IN
C664
Q548
Y OUT
R727
C656
R717
TO IC1301/32
SELECT OUT
J502
FRONT VIDEO 2 J3201
ALL ZENERS ARE UDZ - 10B
12.2TVP14
6/5/02
FIGURE 12-2 - INPUT SWITCHING
Video Appears In Both Boxes: The main and sub video process paths are working correctly. The MID is sending
the video directly into IC511. The problem is likely located on the BR board. The DRC
TM
circuit on this board is
constantly running and not controlled by the I²C bus. IC511 controls the selection of the video source. If video
signals are present at pins 67, 69 and 69 of IC511, replace IC511. No signals at these pins indicate the BR board
is not sending up-converted video. Check to see if video is entering the BR board and the 3.3V and 5V lines are
OK. If they are present, replace the BR board. It is not serviceable.
Video Appears In Left Box Only: The sub video path is OK. Once again, the DRC
TM
is bypassed. This leaves a
small number of components to check. Begin working your way back from the YUV switch, IC1307. Scope the
video signal path back through the main decoder, 3D comb filter, A/D converter and A/V switch IC until you find
a signal and troubleshoot the isolated component.
Screen Is Still Blank: Assuming high voltage is present and the set in not in AKB blanking, this leaves IC511 as
the cause. It is not able to process video from either of the inputs from the MID
TM
or DRC
TM
circuits. There is no
need to check the RGB output path to the CRT boards. Since the unit is not showing AKB problems, the IK
pulses are getting to the CRTs via this path.
Gray Background Appears With Two Black Boxes: IC511 is OK. This signal is generated by the MID. The main
and sub video paths are not working. Since a failure in both paths at the same time is unlikely, suspect A/V
switch, IC515.
As you can see, the MID
TM
circuit provides an excellent troubleshooting tool for video problems. All of the above
techniques were accomplished by using the very basic video block diagram in Figure 12-1. Block diagrams
providing more detail will be provided in the pages that follow to assist in troubleshooting the isolated section.