Samsung LCD TV model number:LN40D550K1FXZC. No Back light problem. Audio works, Flash light test shows picture. i have changed the Back light inverter with no change.

Do flashlight test - if you can see image you need t con board. If no images seen, inverter board. TV Parts Universal TV Stands DLP Chips ShopJimmy

Perform flashlight test to see if the problem is with the backlights inverter board.

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.

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://electronicshelponline.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.

sir,
even if you changed the back light inverter the fault remain as same, it seems to be the back light LED is damaged carefully remove the outer frame of the panel then dis connect the LCD then remove the frame of the defuser screen , take out plug your TV, check the LEDs

Hi,
Your tv has problem with the back light inverter. As you didn't specified the model number its not possible to know is it back light or CCFL one. How ever i have added video to know hoe to find the inverter check it.

Samsung TV Repair Part Number Identification Backlight Inverters LED...
www.electro-medical.blogspot.com

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://electronicshelponline.blogspot.com/.
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.

The power supply is starting to get weak and if you go to www.partstore.com to get a new one.

This does not seem to be a power supply issue but rather an issue with the backlight inverter board. When the screen goes black, take a flash light and focus it on the screen from a close distance and several angles. See if you notice a very faint image. Try changing the channels to make it more noticeable. Try it and let me know

If your TV is staying on and you hear audio after the picture goes dark, then you have a problem with a CCFL or the inverter circuitry that drives them.

Most likely an inverter problem.

Like a bad xformer (usually fogged up plastic wrapper)

Or a bad cap (bulged, swollen, cracked)

Or maybe a shorted IC or transistor (test for short circuit between the different pins of the device)