When i first turn TV on the LG logo shows then screen goes black with audio playing. I can see tv when i point the flash light on it. Will the Power supply board of LED lights fix the problem? Took back cover off and have zero LED lights working. Tv MODEL lg tv 47ln5700-uh
Chances are you have bad lamps in the panel...you will need to take the front cover off and get under the panel and test them and see if some are bad, if they are replace the strip...good luck as its not all that easy to get the panel off and back on without damaging it, use extreme care handling it or once you get the lamps working the panel can be damaged and then it has to be recycled as it can't be fixed
SOURCE: I have a LG 42LE5300 Led tv when I turn the tv on
if you are getting the logo and snow , I think you are on the wrong channel for programming
SOURCE: How do I determine if it's the LED Driver or the LED lights that are bad on my LG LED TV?
If it was the LEDs, then you should still have some working. My first thought would be the LED driver circuits.
Best of luck.
SOURCE: black screen
one of the step up transformers on the inverterboard can be blow up in the most bad case that only the ccfl above start then you see also the logo by only the working ccfl lamp on the bottom or on the top , then it fall after someseconds down in protection mode , there can be bad capacitors on that inverterboard or and also in the powerboard that may have leaked or are bulged topped the first thing is to look to pull out for 1 or 2 cm the both ccfl lamps only if its easy to handle. so you can see witch part of the lamps most case the ccfls are placed in groups of 2 lamps on the top of the screen and 2 down on bottom of the screen most case 2 lamps in a rail . 8 wires 4 wires bottom and 4 wires top white blue and or white red colored with little connectors totally then you can see if only one of the lambs in a pair will not start otherwise it is impossible to control or a complete pair will not start . the flashlight test was good so the power supply shall be good function orfor the most things but a fuse resistor can be blowup in the line to the backlight-inverterboard but if you look the capcitors and see 10v dc ones are to find replace them allways for 16v oreven bulged or not they are bad choosen to tight tolerance all bulged ones must replaced with a higher dc 16v if bulged found take 25v ones because of to tight tolerance by factory, sometimes there can be another problem but this can be happen but a very small chance that a suppression coil was not good cleaned in the factory proces and there are 2 of them in the inverterboard to find. because it it happened to me 2 times by brands like acer and fujitsu siemens the models haved both a separate poweradapter so not have its own power supply insite. both of the monitors i have bought in 2006 and 2007 second hand and by both replaced only in the separate powersupply the bad bulged capacitors for other capacitors after but both monitors are have had that supression coils problem inpriority when i bought them both defect come from Germany it started and then it stopped but by manipulation with a plastic object carefully move both coils it was starting again so i cleaned the ends of the wire of the coils and oneofthe coils was not good degummed (not fully stripped of the wire insulation) and the soldering timein factory was a little bit to cold ( to short time heated solder bath proces) look for brown places on the print by some active components that no parts are have also bad solderings.
Back - light problem. Check and replace damaged component/s at its back-light inverter board, or replace this board as card basis. If you wish to get some details; check the site linked here. Surf the site with patience. Pull up older posts. It will be best to replace the inverter board as card basis. http://electro-medical.blogspot.com/
To some model sets; especially LED back-lighted types; the back-light inverter circuit will be part of the main power supply board [SMPS]. In such cases, the power supply board might need replacement. To some models sets, the back-light inverter and SMPS section circuit will be integrated at its main board itself. If so; the main board should be replaced. To some models of sets, all these section circuit will be integrated at its main board. If this is the case, you have to replace the main board.
I had the same model with the exact same problem last week in my shop, it turned out to be a firmware issue, went online downloaded the firmware to a flash drive and into the TV and it worked fine after that, not saying this is your problem but I had checked both the power board and main and found nothing bad so that is when I reverted to the firmware issue
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