LG 42PT85-ZB (CHASSIS:PD74A) Service Manual ▷ View online
- 13 -
TROUBLE SHOOTING GUIDE
1. Power Board
1-1. The full flowchart for the voltage output
Start check
Manufacture’s model
passage
1. Check the Power Off
status.
Does the whole
screen appear?
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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1-2. 42” Power Board Structure(670990001A)
(1) Pin Layout
(2) Pin Spec
CN1
P1
P2
P3
P11
P12
AC INLET
ANALOG & DIGITAL BOARD
PDP MODULE
AC
NC
AC
YH396-03V
AC Det
RL-ON
STBY 5V
GND
Vs-ON
5V Det
M5V-ON
STBY 5V
GND
NC
6V
GND
3.4V-ON
SMW250-13P
19V
19V
GND
GND
6V
GND
3.4V
GND
12V
GND
SMW250-10P
3.4V
3.4V
GND
GND
6V
6V
GND
GND
12V
12V
GND
GND
SMW250-12P
Vs
Vs
NC
GND
GND
Va
GND
5V
YH396-08V
5V
GND
Va
GND
GND
GND
NC
Vs
Vs
YH396-09V
1
2
3
4
5
6
7
8
9
10
11
12
13
Wafer P/N
NO
- 15 -
1-3. 42” Power Board Structure(EAY32927901)
(1) Pin Layout
(2) Pin Spec
CN1
P1
P2
P3
P11
P12
AC INLET
ANALOG & DIGITAL BOARD
PDP MODULE
AC
NC
AC
YH396-03V
AC Det
RL-ON
STBY 5V
GND
Vs-ON
5V Det
M5V-ON
STBY 5V
GND
NC
6V
GND
3.4V-ON
SMW250-13P
19V
19V
GND
GND
6V
GND
3.4V
GND
12V
GND
SMW250-10P
3.4V
3.4V
GND
GND
6V
6V
GND
GND
12V
12V
GND
GND
SMW250-12P
Vs
Vs
NC
GND
GND
Va
GND
5V
YH396-08V
5V
GND
Va
GND
GND
GND
NC
Vs
Vs
YH396-09V
1
2
3
4
5
6
7
8
9
10
11
12
13
Description
NO
- 16 -
2. No Power
(1) Symptom
1) Does not minute discharge at module.
2) Non does not come into the front LED.
2) Non does not come into the front LED.
(2) Procedure check
Is the power cord plugged in?
Plug in the power cord.
Yes
No
Is the Line Filter and Power
Board Cable connected?
Connect the Cable.
Yes
No
Is the appropriate Fuse(F101) on
the Power Board?
Replace the Fuse.
Yes
No
Is the Power Board and 13P of
VSC Board Cable connected?
Connect the Cable.
Yes
No
After removing the cables, connect them to the Power Board(except the
SC101 connection cable), and change the AC voltage marking to manual.
When ST-BY 5V does not operate, replace the Power Board.
SC101 connection cable), and change the AC voltage marking to manual.
When ST-BY 5V does not operate, replace the Power Board.
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