Question about Samsung LNT4066F 40 in. LCD Television
When I turn on my LNT4066F, the backlight comes on for a couple of seconds and then goes out. TV stays on, and if I hold a flashlight at 45 degree angle I can see a picture, sound works fine, and blue power light stays on.
What do i need to replace or repair?
Thanks in advance
You need to make sure the 24v supply (CNM802 & CNM803 on the power supply) is staying up when the backlight drops out. You will be able to see the light through a few holes if you have the TV on its face with the back cover off. If the 24v stays steady and is not bouncing more than a few volts, your power supply is OK.
Next, you need to find the Sw-Inverter (5 wire cable to power supply) signal which comes from the main PCB. See if stays HIGH (5v or so).
Last thing... you need a tool... a cheap AC detector:
You need to see if the inverter transformer is staying ON:
Put the pen next to it and see if it still detect high voltage when the backlight shuts down.
If you have the 24v and it's good... and the ON line is good... and you have HV detection on the inverter transformer, you have a bad CCFL tube in the backlighting system. If this is the case, you would have to replace the panel. If the 24V line is bouncing around and dropping more than a few volts or your HV detection drops out, your power supply is bad. If the ON line is cutting out, you probably have a bad main board... inverters don't typically feedback errors to the main board. So if the main is shutting the ON line down, it's suspect. I hope this was helpful, best wishes.
Posted on Apr 27, 2010
Replace back light inverter board to get continue back light to view lcd screen image.
Back light inverter board turns off for some reason and no schematics are available to repair it on component level so have to replace complete board.
Check with local tv repair shops as they might have spare board for you.
Hope this info will help you.
Posted on Apr 26, 2010
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Posted on Jan 02, 2017
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