Sony KDP-57XBR2 Training Manual page 113

+200V
R739
L731
Q722
D731
CN731
C733
G
7
R733
Q731
R735
R746
FROM
IK
CLK 1
A BD.
Q734
CN204
CN732
IkR
1
IkB
1
3
9V
CN733
Troubleshooting AKB
The introduction of self-diagnostics was a great feature to assist in analyzing video problems. Prior to that,
several checks needed to be made to verify whether the AKB circuit was the cause of no video. The timer LED
simply blinked at one-second intervals, indicating a problem but not where it was located. High voltage and
vertical deflection had to be checked first. The newer models incorporating diagnostics will flash the timer LED
at intervals of five, followed by a three second separator. Any failures in vertical deflection or high voltage will
appear in the diagnostics well before AKB is expected.
There are three primary causes for an AKB error to appear:
1. One or more of the cathodes is drawing insufficient or no current.
2. One or more of the return pulses are not making it back to the AKB circuit.
3. The AKB circuit is malfunctioning.
Different approaches to diagnosing this problem are available. Some technicians have developed practical
methods to accomplish this and should continue using them if they are effective. The troubleshooting steps in
this chapter are a refined process. AKB problems should be located in less than 10 minutes.
D732
R736
C735
D733 D734
R736
C734
R737
D735
D736
R747
FIGURE 27-1 - CRT DRIVE (CG)
27. Troubleshooting the AKB Circuits
R742
R741
Q733
11
10
G2
9
G1
k
8
H
7
SG732
R743
C737
110
G2
R732
1
CN737
SG731
C732
CG BOARD
G1
FROM
F
1
FOCUS
BLOCK
H G1 G1
6
4
5
CN734
9
TO
7
G BOARD
CN503
6
R753
CN735
9
TO CR
7
BOARD
CN702
6
TO CB
6
R744
BOARD
7
CN762
CN736
27.1TVP14 6/19/02
TO FOCUS
BLOCK