37LG7500 (CHASSIS:LD86F) - LG TV Service Manual (repair manual). Page 14

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- 14 -
TROUBLESHOOTING
1. Power Board 
1-1. The full flowchart for the voltage output
Start check
Manufacture enterprise
meaning of passage
1. Check the Power Off
status.
Does the whole
screen appear?
Is it 
identical to when the
power is off?
No
Yes
No
Yes
Yes
Yes
Yes
2. Check the Interface
signal status.
Is the Interface 
signal operating?
Yes
3. Check the St-by 5V
signal circuit.
Does the 
low pressure output
appear?
Does the 
St-by 5V signal 
appear?
No
No
Yes
4. Check the 5V Monitor
signal circuit.
Does the 
5V Monitor signal 
appear?
No
7. Check the VSC Vs_ON
signal 
Does the 
high tension output
appear?
Does the 
VSC signal Vs-ON
appear?
No
No
Does the
high tension output
voltage occur?
When
removing  the Y B/D
Module input connector,
does output voltage
drop?
When the
Y, Z B/D Module
input connector, does
Power Board high tension
output voltage
drop?
No
No
No
9. Check the Power
Board Output high
tension circuit
Yes
10. Check the Z B/D
Module output circuit
Yes
When 
removing the Z B/D
Module input connector,
does output voltage
drop?
11. Check the Y B/D
Module output circuit
Yes
Yes
8. Check the Vs, Va
voltage output circuit.
Does the 
Vs, Va voltage output
appear?
No
Yes
Yes
5. Check the VSC RL-ON
signal.
Does the 
VSC signal RL_ON
appear?
No
6. Check the VSC low
pressure output
Does the 
VSC low pressure
output appear?
No
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