Toshiba CN27E90 Technical Training Manual page 107

TROUBLESHOOTING CHART OF POWER CIRCUIT
10
Instantly turns ON and
then turns OFF immediately
1
Check/Repair
T840, D840
2
Check/Repair
T840 or 5V-1
using circuit
3
Check QA01
(pin 7), QB30
4
Power LED
blinks in red.
YES
5
Voltage across C884
jumps instantly to
140V or more
No
6
Z801 makes over current protection circuit,
X-RAY protection circuit and +27V over
voltage protection circuit operate
7
Check deflection
circuit
No raster
9
YES
Fuse F801 breaks
No
Fuse F860 breaks
No
11
Check relay SR81
12
NG
Check voltage across
C840
OK
13
No
Voltage at pins 4
and 5 5V?
YES
14
No
Is base voltage of
Q843 high level? (4.3V)
YES
15
Check/Repair Q843, SR81
16
Check/Repair Q801, D883,
D884, Z801, R883, R884,
Q862, R864
17
Check/Repair AC circuit
18
Is the following
YES
point short?
#1-#14, #1-#15,
#14-#15 of Q801
No
19
OK
Voltage across C810
20
Does pin 15 of Q801
operate in switching?
OK
Instantly switching
and then stops
immediately
21
Voltage across C889
OK
22
Voltage across C897
35
Check peripherals of start
circuit Q430 and audio Vcc
36
Check R920 and
CRT Drive board
107
23
Replace F801
24
YES
Replace
Q801, F860
25
Replace F860
26
Check/Repair
NG
D801, R810
C810
27
NG
Voltage across C868
28
Check/Replace
Q801, C870, T862
30
Check/Repair Q801, C862, Q862
Z801, D883, D884, R864
32
NG
Check/Repair F899, D885,
D886, audio power line
33
NG
Check/Repair F890, D891, D892
34
NG
Is voltage at pin 22 (H-Vcc)
of Q501 9V?
37
NG
Does heater light?
38
Check peripherals of
Q501 and video out circuit
31
NG
Check/Repair
C868, D864,
R871, D876,
R861
OK
OK
OK