20" lg LCD backlight turns off after about 5 seconds of use.

Good Luck.

replace inverter board or power supply!

hi good day
before you come up that the main board was the problem lets verify first to narrow down where the problem came from. now as you said you have been tried to put a backlight just to know if their is a problem with the backlight but still you have black screen so which mean the inverter ballast is possibly good as will as the backlight. ok here is on how will you trace the main cause you need to turn on the tv unit then check if their is a INV_ON voltage around 3.3V coming from processor going to inverter ballast, now if do not have voltage turn off the unit then disconnect the connector going to the ballast board and turn on the unit check again the INV_ON if still no voltage come out you have bad processor from the main board. now if the case is the INV_ON voltage is present their is a shorted component at the ballast board that is why the screen is going black after you turn on. if their is an error detected the main board will cut off. hope this will help you thanks for consulting through fixya god bless.

Tv have 2 long LCD inverter boards it probally require replacing.These 2 long LCD inverter boards job are to provided the tv LCD screen panel to have a backlight to the tv LCD screen panel to produced a picture.Tries websites like Shopjimmy.com,Ebay.com to buy those refurbishes 2 long LCD inverter boards for the replacement.

0ne of 3 has failed:
(in order of probability):

1. Backlight inverter
2. Power Supply
3. Backlight

More specifically on #1 and #2 - capacitors either bulging, leaking, or exploded.

Please seek the expertise of an experienced TV repair technician - as they contain potentially lethal voltages that must be properly discharged before work can begin.

Thanks!^%$

Now,the tv is turn on,the picture come on only for a few sec.than died,you still have sound left?Yes,than ur tv have 1 or 2 a long board call the LCD inverter boards is dead.These 1 or 2 long LCD inverter boards help the LCD picture screen panel to have a backlight to produced a picture.Tries websites like Shopjimmy.com,Ebay.com to buy those 1 or 2 long LCD inverter boards for the replacement.

Here is a link for the manual - it might help - http://tv.manualsonline.com/manuals/mfg/lg/26lc7d_26lc7dc_32lc4d_42lc4d.html

Is it under warranty?
You may have either the power supply problem or backlight inverter board problem, please se my pictures and troubleshooting guide below:
http://s807.photobucket.com/home/budm/allalbums
http://en.wikipedia.org/wiki/Capacitor_plague
http://www.fixya.com/support/r5093881-lcd_flat_panel_tv_troubleshooting_guide
Parts: try www.shopjimmy.com or Ebay

Ur LCD inverter backlight board is dead.Replaced this LCD inverter backlight board will solved this problems.Tries Websites Shopjimmy.com,Ebay.com to buy a refurbish LCD inverter backlight board for the replacement.The board is a long in shape.