LG 55LN5310 dead

[tech2014]

Customer told me something got thrown at the screen and then the tv went off and it is completely dead, no power LED at all. She said the object was a foam ball and that it hit the bottom of the screen, on the frame not LCD.

I tested the power supply and the PWR-ON is 0V. I checked the voltages on the main board and they are all jumping around. I jumpered 3.5V into power supply board and all voltages come up on power supply, but they are not stable and jump around.

Would this point to a bad main board?

[martino]

Re: LG 55LN5310 dead

When you disconnect all boards,then force on the power supply,how are the voltages then?
First was thinking that a ccfl tube could have broke on impact,but it's a LED lol

[tech2014]

Re: LG 55LN5310 dead

I get voltages but they are not stable, jumping around. I even checked the 24mHZ crystal on the main board and it is measuring 24MHZ but the waveform is jumping around just like the voltages. With everything connected, I get close to 3.5V on the power supply connector but they are not stable.

[martino]

Re: LG 55LN5310 dead

DISCONNECT all board from power supply,then force on power supply,are voltages stable then? As in without all other board?

[tech2014]

Re: LG 55LN5310 dead

no. I used my external regulated DC p/s and put 3.5V on PWR-ON pin. Voltages are there but jumping around, unstable.

[tech2014]

Re: LG 55LN5310 dead

UPDATE

I found another LG power supply with the exact same pinout as the power supply I am testing. I out 3.5V in and all my voltages were good and stable. I then did the same with the one i am working on, and I found that even the PFC voltage is jumping around and not stable. It is obviously a p/s issue. Only problem is there are a tonne of surface mount components on the back of the board.

[dick_barton]

Re: LG 55LN5310 dead

Any pictures of the power supply available?

[Moreno83]

Re: LG 55LN5310 dead

I had the same issue with a samsung led. Also jumping voltages. Heating up the powersupply works , tv will turn on....

Try to heat up the optocouplers area and see if tv will turn on....
I just replaced the PS and tv worked again! I replaced all caps and even the opto's but i never found the real problem...

Hope you can pin point the exact issue!

[Diah]

Re: LG 55LN5310 dead

i think the problem at booting voltage, is it chassis LA32B ?

make sure Micom voltage on L301 +3.5V_ST. if less or unstable change it.

also as i think the CLK Is 10MHz not 24MHz as you wrote.

[tech2014]

Re: LG 55LN5310 dead

Here are pics of the power supply.

[budm]

Re: LG 55LN5310 dead

LG EAY62810701 (3PAGC10124A-R) Power Supply / LED Board
http://www.shopjimmy.com/lg-eay62810...upply-unit.htm

So this the board, right?
Pictures provided by shopjimmy.

[tech2014]

Re: LG 55LN5310 dead

LG EAY62810701 (3PAGC10124A-R) Power Supply / LED Board
http://www.shopjimmy.com/lg-eay62810...upply-unit.htm

So this the board, right?

yup

[budm]

Re: LG 55LN5310 dead

So the 3.5VSTBY is not stable at this point, right? The transformer T501 that generates the 3.5VSTBY also generates the dc (AUX winding of T501) through the switched (Q501) Voltage to provided VCC for running PFC Controller IC and the other SMPS IC.
You already inspect the board real close for any bad solder joints?
You can try heating up those small caps in the primary side by the 3.5V stby IC to see if the 3.5V will be steady and the PFC Voltage will be steady, see post 11.

[tech2014]

Re: LG 55LN5310 dead

yes, checked for bad solder joints, all seems ok.

So this is a power supply problem like I suspected?

[budm]

Re: LG 55LN5310 dead

Well, if I understand you correctly, the replacement power supply board is installed and the TV function and you have steady PFC Voltage, steady 5.3V STBY, etc, right?

[ReeceyBurger123]

Re: LG 55LN5310 dead

Before you do any type of repair does the Lcd look smashed ? You can tell by shining a torch on it.

[tech2014]

Re: LG 55LN5310 dead

The replacement power supply I tested has the exact same pinout as the original power supply. Will it hurt anything if I install this p/s into the tv to see if the power comes on.

The replacement p/s is part number EAX65423801. Here is a link to it on shop jimmy.
https://www.shopjimmy.com/lg-eay6307...-led-board.htm

[budm]

Re: LG 55LN5310 dead

That is not the same setup as the one we are working on at all.
Good question abut the screen by reece.
If you look at the Voltages chart on the board, the LEDs Voltage is not the same.

[tech2014]

Re: LG 55LN5310 dead

yeah I just noticed that budm. I think I may just order a new power supply since there are too many surface mount components on the board and without a schematic, its too difficult to repair.
Also, there was no damage to the screen as far as I can tell.

So does everyone agree with me that it is a p/s problem?

[budm]

Re: LG 55LN5310 dead

Did you try running the the TV board without the T-CON board connected to the main board? I cannot see how foam ball hitting the frame of the TV can knock out the TV.