High Voltage Circuit Troubleshooting - Sony KDP-57XBR2 Training Manual

Chapter 19 - RA-5A High Voltage Circuit Troubleshooting
Overview
Figure 19-1 illustrates a block diagram to give an overall view of the circuitry on the D board for generating high
voltage. The main components consist of a regulator stage to vary the B+ level to the flyback transformer for HV
level control, a driver and output stage to switch the flyback on and off, a flyback transformer to generate HV and
a LOT transformer to generate heater voltage and 200VDC for CRT cathode bias.
IC8008 is a PWM generator and driver to control the on and off time of HV regulator Q8035. The sawtooth
waveform for the PWM generator is synchronized to the horizontal drive pulse at pin 14 to provide a stable
reference. A sample of HV level is taken from the HV block assembly and enters pin 12 to provide an error loop
by which to vary the duty cycle of the drive pulses to Q8035. Q8038 provides the necessary switching to turn
T8004 and T8005 on and off and maintain a HV level of 31KV.
HV level and current are monitored by IC8006 and IC8007. They will stop high voltage generation to provide
protection for the HV components, CRT's and X radiation level. This is accomplished by disabling the H drive
pulse from video process IC3006. Both the HV level and shutdown threshold are shown as adjustable by
VR8001 and VR8002 but these controls are sealed with epoxy at the factory and are not adjustable.
+135V
SEC.P.S
G BD.
IC6001
(G BD.)
9
CN6106/
CN8013
+135V
H OUT
REG.
D BD.
Q8027
H DRIVE
Q8023
CN8004/
CN3005
10
A BD.
IC3006
VIDEO
PROCESS
+135V
+135V
1 1
CN3001/ CN3023/
CN9001
CN9001
V BD.
VEL MOD COILS
1 2
CN8016
+12V
1 12
VR8001
18
5k
IC8008
HV
PWM GEN.
6
14 10
DRIVER
Q8004
Q8016
Q8019
Q8020
40 10
CN3007/
DRIVERS
CN8006
Q8005,
Q8032
+15V
1
R8198
CN3010/
10k
CN9001
D BD.
FIGURE 19-1 - HIGH VOLTAGE STAGE - RA-5A CHASSIS
19. RA-5A High Voltage Circuit Troubleshooting
Q8035
R8196
S
HV REG.
P
3
CH
C8118
D
D8029
MIX OUT TO
Q8038
IC8007
HV OUT
DRIVER
8.1V
Q8036 N
G
R8160
Q8037
D8031
D8034
18V
3
IC8007
Q8022
PROT. 1
7
5
Q8021
5
IC8006
7
PROT. 2
3
D8015
LATCH
80
HV BLK
7.46VDC
3 4
R8171
100
D8036
15V
12
7
LOT
14
T8004
D8039
D8030
200V
1
T8005
1
FBT
D8035
2 11
C8142
ABL
D8023
Q8028-9
ABL
D8025
R8223
R8153
PROT.
VR8002
D8017
100k
CRT
HV
CN8022/ 200V TO
VIDEO
CN7304
1 OUT B+
C B BD.
6
R8219
D8038
CN8021
1
R
2
19.1TVP14 7/17/02