Lg 55lm5800uc 3d led tv no power blinking led

[braxton]

I picked up this 3D 2012 model TV and previous owner said it just turned off while watching tv.
When the power button is pressed, the red LED flashes slowly 2 times and then goes out. No relay clicks or any other signs of life. There is not much info online about this problem. Based on the fact that main boards for this model are very expensive and hard to find (and there are sites offering main board repair service for $200 for this model), my guess is the main board is the problem.

Does anybody have any experience with this model and have any suggestions as to what to check on the main board?

[budm]

Re: Lg 55lm5800uc 3d led tv no power blinking led

You can start by uploading good clear pictures so we can see all the boards and how all the boards are connected together, then you will need to do good visual inspection and then Voltage checking at the connectors.

[braxton]

Re: Lg 55lm5800uc 3d led tv no power blinking led

Here are pics of the main board and power supply already removed.
There is 3.5V standby on the power supply but that's about as far as it gets...
Visual inspection does not reveal any burns or bulging caps.

[braxton]

Re: Lg 55lm5800uc 3d led tv no power blinking led

this is hopefully a clearer pic of the main board

[budm]

Re: Lg 55lm5800uc 3d led tv no power blinking led

If the PWR-ON pin on connector P201 the the main board is not sending the PS-ON to turn on the main power supply and since you also indicated all other pins are showing 0V but you do have 3.5VSTBY Voltage then it points to the main board.
Did you try disconnected all other boards to the main board but still have the Power board and the Power button board connected to see what happen?

[braxton]

Re: Lg 55lm5800uc 3d led tv no power blinking led

If the PWR-ON pin on connector P201 the the main board is not sending the PS-ON to turn on the main power supply and since you also indicated all other pins are showing 0V but you do have 3.5VSTBY Voltage then it points to the main board.
Did you try disconnected all other boards to the main board but still have the Power board and the Power button board connected to see what happen?

Yes, with the T-con and speaker cables disconnected from the main board (and also tried LED cables disconnected from the power supply), the result is the same.

[Diah]

Re: Lg 55lm5800uc 3d led tv no power blinking led

here the SM . follow the 3.5 volts on main board page 16

[braxton]

Re: Lg 55lm5800uc 3d led tv no power blinking led

here the SM . follow the 3.5 volts on main board page 16

Thanks! I will follow up when I get a chance to further diagnose...

[braxton]

Re: Lg 55lm5800uc 3d led tv no power blinking led

Just to follow up. The troubleshooting process, by following the service manual, suggested the power board was the likely culprit. This was not what I initially expected. I began searches using the power board number and discovered that a ceramic cap C603 and diode D607 often get shorted. Sure enough these two components were shorted on my board.
Awaiting arrival of new components from Digikey to do further testing...

[budm]

Re: Lg 55lm5800uc 3d led tv no power blinking led

That is why were you sure that you do not have the PS-ON signal since you do have the STBY Voltage, the C603, D607 are part of the PFC Voltage booster circuit, when those parts failed you will not have boosted Voltage for the main SMP power supply section.

[braxton]

Re: Lg 55lm5800uc 3d led tv no power blinking led

Success!

To quote Mike Mallo on youtube:
"
A search of the part # of this board "EAY62512801", will bring up a schematic of "Revision 2" of this board. The only change is D607 is upgraded from the mentioned 4 amp diode MUR460AG, to a 10 amp rated diode. Part number of the new diode is STTH10LCD06FP. I've replaced mine with the new part, and it works well now. It is a different style package, a TO-220 instead of the axial type. So it took a little creative soldering to get it to fit on the Revision 1 board. Also it has to be kept below the maximum component height of 15.5 mm. One leg through the board, and a short jumper to the other leg works well.
"

So I installed the upgraded 10A diode component and also upgraded the cap from 200pF 1KV to 200pF 2KV and the TV works well!
I've attched a pic of the board with new components.

[cody2016]

Re: Lg 55lm5800uc 3d led tv no power blinking led

Hi I am having the same problem, my C603 is burnt out. I saw that you said you upgraded that as well. did you mean 220pF 2kV? or did you change it to a 200pF? Is there anyway that you could let me know what the part number was for the capacitor that you bought from digikey?

Thank You

[iDIYit]

Re: Lg 55lm5800uc 3d led tv no power blinking led

Hi I am having the same problem, my C603 is burnt out. I saw that you said you upgraded that as well. did you mean 220pF 2kV? or did you change it to a 200pF? Is there anyway that you could let me know what the part number was for the capacitor that you bought from digikey?

Thank You

For anyone who finds this thread like I did, this repair worked for me. I upgraded the D607 diode (P/N: STTH10LCD06FP), and used a 220pF 1KV capacitor at C603 (P/N: C322C221JDG5TA).