LG 42LG60 Series, Training Manual

Page: 21 / 87

Fall 2008 LCD Training
21
3
2
L
G
4
0
Fall 2008 LCD Training
21
CIRCUIT DeSCRIPTIONS
POwER SUPPlY TEST
The Power Supply must be producing
STAND-BY +5V before performing this
test. With the Power Supply disconnected
from other boards and AC applied, confirm
that the Power Supply is producing 5V
from either Pins 9, 10, 11 or 12. If not, check the fuse. If the fuse is ok and there is no
5V, replace the Power Supply. If 5V is ok, continue.
1st short either pin 9, 10, 11 or 12 (5V) to pin 19 (PWR) using a 10K resistor. The P201
connector should be disconnected from the Main board and AC not applied when adding
the jumper. Re-apply power when testing.
Confirm that the other low voltage power supplies are activated.
Pins 1 and 2: 16V
Pins 5 and 6: 12V
Pin 18: AC Detect goes high
Fuse F101: Check for 350V (Ballast Voltage)
If any voltage missing, replace the Power Supply. If the 1st test was successful, leave the
10K resistor in place.
BACklIGhT TEST
To test the Backlights, leave the 10K jumper in place from the previous test. Plug in the
Backlight plug P203 and apply AC power. Observe the Backlights. If normal, LED1 on the
Ballast board should turn on first, then the backlights should turn on and LED1 should
go off.
If no backlight activity, confirm the Fuse F101 has approximately 350V on both sides.
If only on one side, check fuse for open. If no 350V on either side, replace the Power
Supply. If 300V is present, check P203 for 24V on pins 1-5. Check P203 pin 12 for at
least 3V (Inverter On/Off). If yes, confirm connectors to backlight are ok, if ok, then the
panel is defective.
P2
3 1 7 5 11 9 15 13 19 17 23 21
4 2 8 6 12 10 16 14 20 18 24 22
+5V PWR
10K
P2
3 1 7 5 11 9 15 13 19 17 23 21
4 2 8 6 12 10 16 14 20 18 24 22
+5V
PWR
10K
INV