Lg42lc2d i has no sound or picture

I have no idea why you would change the tcon board if you don't have sound but your not the first person to do that. 1st thing to do...power the set on and look at the back and see if the optical output plug is lit red, if it is your power supply is working. If it's not check the 5 volt standby, if no voltage there replace the power board, if you see 5 volts and have no action it could be connectors or plugs in the LED circuit, did your old led strips test bad?

Likely the diodes are also blown, and are what caused the capacitors to blow.

Board # 3655-0122-0150 is the main board not the PS board as mentioned in the previous message it can be purchased from shopjimmy but its not a cheap board...below is the URL for the board..How does the set behave? sound no picture, picture no sound, dead, has standby light, poor picture...ect
http://www.shopjimmy.com/vizio-3655-0122-0150-main-board-for-xvt553sv.htm

The Ballast board that controls the backlight is next. Sounds like it has failed.

Main board fault. The start voltage does not comes to power board from it. If you wish to get some details; check the site linked here. Viewing it in "Mosaic" or "Magazine" will make surf easy. Pull up older posts. Surf the site with patience. Do a search by type in the brand name of your device at its search box and press "Enter".
http://electronicshelponline.blogspot.com/

Sanyo TVs usually only have two boards in them , doing a visual inspection of the power supply capacitors usually reveals swollen or bulging capacitors.
If the capacitors look good, voltage checks would be needed to isolate the problem to either the main board or power supply. Check for 5 volts to the IR board (& or keyboard) , if five volts is present suspect the main board

I’m happy to help further over the phone at https://www.6ya.com/expert/eric_ab7c09ec01841771

Hi, it could be bad inverters or a bad power supply. I'd inspect both boards. you should have 24 volts coming from the power supply to the inverter. If you have the 24 volts, bad inverter. If you don't have the 24 volts, bad power supply.

The inverter is the high voltage board that provides variable power to the backlight lamp. This is the most common. When inverter is faulty you can get no picture, or a very dim picture that can only be seen by pointing a torch light with a 45 degree angle on the LCD surface from very near distance. The inverter must be tested by reading voltages with a multimeter.

If there is still about ? 24. Volts coming from the Power Board when it goes dark, it will be the Inverter board that needs replacing. If not, it is the Power Board that needs replacing. The Voltages should be written next to the sockets & plugs on the Power Board.

If you see the back light, then you should have 24vdc on the main power supply board which it gets the turn on command from the maun board. If you do have all those voltage, then it does sound like you need the new main board.