LG Model 55LW5000 Power Up Issue

[ikmpch]

I am trying to repair LG TV Model 55LW5000.
At plug in, the red LED blinks twice and then Blue LED lights for a second and then its all dead. Opened the back cover and measured the voltages at the power connector pins with all cables attached. Here are the results:

At pin 1 = 3.3V (PS-ON)
At pins 2,3,4 = 24V
At pins 9,10,11,12 = 3.5V (ST-BY)
At Pins 17,19,21 = 12V
At pin 18 = 0V (DRV-ON)

Main CAPS (4 of them) = 396V
Fuse F100= 120VAC, F101= 395VDC, F501=395VDC

All most all voltages present but the set does not go into standby? It looks the set is in 'RUN' mode but only dead!

Tests:

1- Disconnected Power supply connector. Plugged in the TV and measured ST-BY voltage on pins 9,10,11,12 = 3.5volts.

2. Jumped pin 9 to pin 1. Got PS-ON=3.3. Pins 17/19/21 = 12V and pins 2,3,4 = 24V. Also got 55V on backlight connectors.

3. Put in a second jumper from ST-BY to pin 18 (DRV-ON) and the backlight lit up. It suggests that individually the P/S board and inverter circuits are working.

4. T-CON is missing 12V input

Why DRV-ON is 0? No Supply to Inverter. What is reason that set goes into such a mode with just plug in and does not even go into standby?

Is it a firmware issue (bad EEPROM)?
Is it a MICOM (micro controller issue)? There is a reset option on the mainboard. How can it be reset?
There is an ERR OUT pin (pin 24) on PS connector. What is the purpose of it? Is it possible it is shutting the power supply with this two blink code.

Your input will be greatly appreciated. Thanks.

[alfatv]

Re: LG Model 55LW5000 Power Up Issue

Haven't seen this model, but on LW5700 the typical failure is solder joint cracks on main board BGA (under heatsink).

[neilc6]

Re: LG Model 55LW5000 Power Up Issue

Yes LE, LV, LW and LS series all have BGA issues with the main board. You can test by heating it up with a hair dryer before plugging in. Search for repair services on ebay.

[ikmpch]

Re: LG Model 55LW5000 Power Up Issue

Thanks guys. My plan of action:
1. Test the ICs that supply 1.5, 3.3, 1.26 & 2.5V regulated power on the main board.
2. Cut the ERR_OUT wire and see what impact it has on the TV power up.
3. Heat all 4 BGA chips on the main board.

I shall post results of my tests.

[ikmpch]

Re: LG Model 55LW5000 Power Up Issue

Update:
I checked various voltage regulator ICs on the main board and some were dead and others had .05 volts or so.
I cut the ERR_OUT wire and it did not help.

I heated all 4 BGA chips. The TV did not turn on. Some of the voltage regulators did show some life. Heating/reflow using flux did not help. The owner had baked the board twice in the oven previously. Giving the TV back to its owner for disposal.