How to troubleshoot and repair Power board of LG42LE5500 LED TV
Part number:
EAY60803101
POWER SUPPLY SECTION
This switch mode power supply develops Stand By 3.5V at all times when AC is applied.
At power on, it develops 12V and 20V for the Main board.
It develops 120V for the LED Backlights
This power supply draws less than 1 watt during stand by mode. The fuse F101 and F103 reads 7.6V (from hot ground) during this time.
When the controller chip receives the PWR-ON command 3.36V via P201 Pin 1, the primary section increases its current supplying ability. Both Primary fuses F101 and F103 now read a little more than 395V.
T102 delivers AC to D206 which develops the 120V for the LED backlights.
P201 Connector: (To Main Board)
12V (11.43V) is routed out P201 pins 17, 19 and 21 and 20V (21.27V) is routed out P201 pins 2, 3 and 4.
P204 Connector: (To Panel LEDs)
120V is routed out P204 pins 1 and 12.
P205 Connector: (To Panel LEDs)
120V is routed out P205 pins 1 and 12
Power Supply
Start Up Sequence Click on the pictures to magnify
42LE5500
Television Turn On Commands Circuit Drawing.
Power Supply
Board Low Voltage Test
AC Should not
be applied at any time while adding jumpers or While unplugging connectors as
damage to the circuit Board may occur.
a) When AC is applied, the SMPS “MUST” be producing STBY 3.5V on pins 9, 10, 11 or 12 of P201.
If 3.5V Standby is not being generated, the SMPS is defective and must be replaced. There is no need to continue with the next test. But, make sure AC is arriving at the connector SK101.
(b) Unplug P8000 on the Main Board to make insertion of the Jumpers easier. Use P700 Side to insert resistors.
a) When AC is applied, the SMPS “MUST” be producing STBY 3.5V on pins 9, 10, 11 or 12 of P201.
If 3.5V Standby is not being generated, the SMPS is defective and must be replaced. There is no need to continue with the next test. But, make sure AC is arriving at the connector SK101.
(b) Unplug P8000 on the Main Board to make insertion of the Jumpers easier. Use P700 Side to insert resistors.
No Back-light during this test
Add a jumper
between (3.5V STBY) pin 7, 8, 9 or 10 and Pin 1 (PWR_ON). Apply AC.
This will turn on the power supply, relays will click.
a) Check that the 24V and 12V power supplies are turned on,
* P201 (12V pins 17, 19 and 21)
* P201 (24V pins 2, 3 and 4)
* P204 and P205 (120V pins 1 and 12) to the Panel. (Or check D206 + lead)
(2) Remove the AC power.
This will turn on the power supply, relays will click.
a) Check that the 24V and 12V power supplies are turned on,
* P201 (12V pins 17, 19 and 21)
* P201 (24V pins 2, 3 and 4)
* P204 and P205 (120V pins 1 and 12) to the Panel. (Or check D206 + lead)
(2) Remove the AC power.
Power Supply
Board Back-light Test
Continue if the
1st test was OK.
Leave original jumper in place.
(3) Add another jumper between (STBY_3.5V)
pin 9, 10, 11 or 12 and Pin 18 (INV_On).
(4) Apply AC Power. (Simulating a Power and Back-light On command.)
Leave original jumper in place.
(3) Add another jumper between (STBY_3.5V)
pin 9, 10, 11 or 12 and Pin 18 (INV_On).
(4) Apply AC Power. (Simulating a Power and Back-light On command.)
Back-lights Normal
a) If normal, the backlights should turn on.
SMPS OK, Inverter OK.
Backlights Abnormal:
a) Recheck all connections.
b) Confirm the INV On/Off line pulling up to at least 3V.
c) Check the connections to the Panel.
If the Inverter On command is pulling up to 3V and the 120V is being generated from D206 + lead, See the Inverter Section of the Power Supply for additional checks.
Note: If either P204 or P205 is disconnected, the backlights will come on, but shut off in 4 seconds.
REMOVE AC POWER
42LE5500 Inverter Part of the SMPS
Power Supply Connector P201 Voltages
Power Supply
Connector P204 / P205 Voltages
