LG 50ln5200-ub led TV . Has no picture but great sound . What is the problem ? I did the flashlight test and can see the faint picture which tells me the backlighting is out . This tv model is a Black friday " Wally World Craptastic " model built with the finest parts from the dumpsters at lg so it does not have a seperate inverter board , The inverter is built into the power board. I replaced the power board and still has the exact same symptoms . Any Help is appreciated/ The only other two boards are the t-con board and the main board . Power board has been replaced.

Usually bad power supply, Where did you source your part? return/exchange it. Bad LEDs/ possible but not as likely, Tcon working if you can see images with flashlight. You must also have backlight on signal from main board ,check for 3 to 5v on labeled connecter on power supply. UPDATE---47" & 50" LN series. This model has had LED problems if your TV acts as described by Mr. Hughes in is answer to this problem you have bad LEDs

Can you see the the screen flash brightly when tv is first switched on and then immediately go black?Does the red led standby light then slowly flash twice? If these are the symptoms then I can only tell you that this is the fault I had on my LG .47ln540v tv.I replaced the main board,psu board and t-con board all to no avail.Finally i stripped down the screen assembly and found the problem was caused by a faulty backlight led. Apparently the electronic circuitry monitors the supply to the backlight leds and if it detects a problem it shuts off the supply and goes into a "safe"mode to protect the remaining leds from receiving to much current.One my tv I can only deduce that standby led light flashing twice is a blink code for a faulty backlight,but I could be wrong. Although I am not a tv technician I know enough about electricity to safely work on some repairs,but I cannot recommend others to do the same,there are some capacitors on the psu board carrying high current and charge and could be lethal even when power is disconnected from the tv.I managed to get a replacement led backlight strip from a damaged tv of the same model.It took me about 5 weeks to troubleshoot this fault.Hope this helps someone.