Sony KDP-57XBR2 Training Manual page 54

+12V
R8027
R8031
C8019
H
DRIVE R8021
P R8028
R8010
Q8009
D BOARD
High Voltage Protection
The HV monitoring section utilizes two separate circuits to provide redundant protection.
HV Stop 1: Figure 11-5 contains the paths for the first set of protection components. HV level is monitored from
the HV block by pin 3 of IC8008. This is compared to a reference of 9.3VDC at pin 2. If the high voltage rises
above acceptable levels (34KV), pin 3 will exceed the reference. Pin 1 will go high. The H pulse driving the HV
circuit will be grounded by Q8019 and the high signal will sent to OSD CPU IC1009 to flash the timer LED in
sequences of seven.
Flyback transformer current is monitored by applying the ABL voltage to Q8027. Under normal conditions, ABL
is a positive voltage between 2VDC and 6VDC. If the current rises to an unacceptable level, the ABL voltage will
go lower. Once it drops below .6V, Q8027 will turn off, sending a high to pin 3 of IC8010. The H pulse will be cut
off and IC1009 will respond the same way as the over-voltage condition described above.
C8029
D8015
R8027
Q8010
R8044
R8059
TO
Q8008
FROM
Q8024/C
AND IC8007/1
HV REGULATION
CONTROL
FIGURE 11-4 - HV REGULATION PWM
11. RA-4/4A High Voltage Circuit Troubleshooting
R8067
R8060
R8071
3
1
2
C8045
IC8002
C8033
R8082
+12V
R8074
R8070
Q8016
N
P
Q8015
R8075
51
R8084
+12V
R8015
Q8022
R8085
R8095
R8083
Q8018
N
R8113
R8108
D8023
IC8002
6
7
5
R8077
D8017
R8114
N
C8066
IC8008
6
7
5
-12V
C8064
R8096
11.4TVP14 5/31/02