lg 47le5400 powers up, black screen, no sound

[cherokee.warrior]

I have a lg 47le5400, it acts like it is powering on. when pressing the power button it lights up and all the other button leds come on. I get nothing but a black screen and i get no sound at all. The picture i am adding to this post is the readings from the connector between the power board and the mainboard. I have looked all over the net and i can not find a service manual. one site says it has it but i dont know if the website is legit (servicemanual.pro). Any ideas on what to look for on this make and model.

[sordids999]

Re: lg 47le5400 powers up, black screen, no sound

Pictures of the boards inside the tv may help you more with fixing your tv

[dskall]

Re: lg 47le5400 powers up, black screen, no sound

With flashlight do you see image on screen?

[cherokee.warrior]

Re: lg 47le5400 powers up, black screen, no sound

No image on the screen when using flashlight. Forgot to add that to the post above.

[cherokee.warrior]

Re: lg 47le5400 powers up, black screen, no sound

here are the board images.

[Andrew F. Ali]

Re: lg 47le5400 powers up, black screen, no sound

Main Bd problem. Since the power LED comes on, etc.

[cherokee.warrior]

Re: lg 47le5400 powers up, black screen, no sound

That is what I was thinking. I'm trying to narrow it down to the component level. I've been unable to find a service manual for the TV to trace the problem.

[dskall]

Re: lg 47le5400 powers up, black screen, no sound

If you unplug cable to main board and jumper pwron and drvon to your 3.5v do you get backlights?

[cherokee.warrior]

Re: lg 47le5400 powers up, black screen, no sound

I will do that tomorrow and get back to you all. It's family time at the moment.

[saddle_au]

Re: lg 47le5400 powers up, black screen, no sound

Before doing something like baking the board, I've got a similar one that is from an LN5400 that comes to life temporarily if I chill these parts. There are some funny waveforms around the power detect circuit keeping the CPU off line (note: schematic will be not quite the same but very similar). Am investigating it further right now.

Does yours change if you chill this area?

[tvsteve2]

Re: lg 47le5400 powers up, black screen, no sound

I have 4 sets a 42LE5400, 2each 47LE5400 and a 55LE5400 all are dead (some power the led and backlights work when jumped. All these have a BGA processor under a large heat sink and "cooking" the main does get them to run for a short while. All the used boards and repairs offered are "cooking the board" nobody is reballing them! to complicated and expensive! the LN series has a smaller processor that seems to last.

[cherokee.warrior]

Re: lg 47le5400 powers up, black screen, no sound

Dskall,u did the jumpers as described. I get come clicking everytime I make the connection but I see no backlights.

[dskall]

Re: lg 47le5400 powers up, black screen, no sound

Do you briefly get any voltage on drvon pin at power up?

[cherokee.warrior]

Re: lg 47le5400 powers up, black screen, no sound

I removed both heatsinks off the main board and used foil tape to tape around the chips and on the underside of the board. soaked both chips with liquid flux and heated chips with a hot air gun for a while and put board back in tv. TV now works.

[nwcs]

Re: lg 47le5400 powers up, black screen, no sound

Thanks cherokee.warrior for your tip. I did not have any foil tape handy but I did everything else you said and it fixed my tv too.

[Nick's Tvs]

Re: lg 47le5400 powers up, black screen, no sound

These guys over here don't do reflows but instead the actual reball work.
1 year warranty on the repair as well. When the boards fail in the next few weeks to few months, this will be a good long term solution.

http://www.ebay.com/itm/Repair-Servi...oAAOSw53NZAPps

[leto]

Re: lg 47le5400 powers up, black screen, no sound

Got LG 47LE5400 with the same symptoms: black screen, no picture. The voltages on the cable that supplies power on the main board (there is a table on the white power supply board with voltages and pins) are as expected. I also tried to put 3.5V on PWR_ON and DRV_ON on unplugged cable and got the TV turning on but no backlight.

Ended up heating two BGA chips that are under heatsinks (preheat the whole board for around 100C for 10 min, put flux around chips, heated the chip on 320C for 5-6min, then got down to 200C for 2 min, then for 100C for 2min) and the TV started working. I removed thermal stickers that were put between chips and heatsinks (the one that was on the chip near the R&L LCD cable sockets degraded due to the high temp or time) and put thermal paste, it should increase the thermal contact.

Will see how long the TV will last.

[maxim22]

Re: lg 47le5400 powers up, black screen, no sound

If you unplug cable to main board and jumper pwron and drvon to your 3.5v do you get backlights?

I have the same problem and wondering which board is defective.
Could explain better how to check LED panel please?
Not sure where to connect 3.5V jumpers.

[nomoresonys]

Re: lg 47le5400 powers up, black screen, no sound

Check all the pins on the connector going from powersupply board to mainboard with multimeter, report all voltages, check in standby which is plugged in turned off, then turn on tv, make note of both conditions. Something like pin 1 ps-on 0v off and 5 v powered on, theres a video how to in the second link there in my signature below.

[maxim22]

Re: lg 47le5400 powers up, black screen, no sound

Check all the pins on the connector going from powersupply board to mainboard with multimeter, report all voltages, check in standby which is plugged in turned off, then turn on tv, make note of both conditions. Something like pin 1 ps-on 0v off and 5 v powered on, theres a video how to in the second link there in my signature below.

In PowerOn mode all voltages seem to be OK except PowerOn voltage (pin 1) which is 3.23V instead of 20V (as written on the board).
In StandBy mode there is only 3.4 V on 2 pins (pin5,6), all others are 0V.