Tv powers up for about 1 second and then shut down I have replace the main power board still have problem

PS does not just shut down unless it is defective or there is some short in another location that is telling it to shut down to prevent further damage to components. Which is it? Sure the PS you put in is good? If so, issue is with some other part of the set that you have not already replaced.

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.

Hi Neil
Assuming the power supply is in good order!
I am not familiar with your particular model!
The power supply is either shutting down from too much current draw or it's sensing a fault.
Can the power supply be isolated? Does it work without a load?
This will depend on your connection points.

Power supplies them selves are the cause of most failures in modern TV's as they handle the AC & the load & the temperature etc. Check for puffer up Electrolytic capacitors on the power supply board. Caution... you can get a nasty kick of the AC side.

An Example
How to Replace an Electrolytic Capacitor

Fault with its main board. Short circuited component/s at it. Contact any service technician; or the authorized service center. If you wish to get some details; check the site linked here. Surf the site with patience. Pull up older posts. http://electronicshelponline.blogspot.com/ . In most cases, the main board might have to be replaced. If so, a software [firmware] update too might be necessary.

tThe diagnostic circuits is shutting your TV down. In most cases the set will shut it down immediately. Apparently your set hasn't shut completely down yet. When you turn your TV on the diagnostic circuits send a low voltage, low frequency signal through all the circuits and depending on how they come back whether the sets powers up to full power. If a problem is detected it will shut down to protect the other circuits. It sounds like you might have some capacitors going bad on your power board. A capacitor that is going bad would let it come on for a few seconds then the diagnostic circuits would see the capacitor getting further out of tolerance and shut the set down. If you are a DYS type person you might want to lay it flat of it;s face and remove the back. A bad capacitor will be bulged out on the top. are Replace capacitors with the exact uf value and if you can go above the rated voltage but never below., If this isn't the problem then it is probably the main board (the board where your cable hooks up to), There are other things that cab causes for this but I would check the capacitors first.
Col. Dana Gillespie

That problem is usually have 2 causes..Its either power supply board or main board..

Please take this steps on how to determine the problem:
1. Open the back cover.
2. Check the power supply output...It should have 5vdc for the main board..12vdc or 16vdc for the audio and 24vdc for the back-light inverter..
3. If those 3 voltage supplies have encountered voltage drop...The problem could be on power supply board..
4. If the power supply output is normal..The problem could be on the main board...
5. If the problem is power supply you should check if the capacitors are bulged on the top and try to replaced it..If you can't do that you can purchased new power supply board..
6. If the problem is on main board there is no D.I.Y repair on that so you need to buy a new main board that fits to your TV..
Hope this solution will be helpful..

Thanks for using fixya...

Hello
There are two main reaons for this fault. The first is with its power regulator board itself. If it has any loose soldering points developed, this type of intermittent fault can occur. The second is with its light engine. If you want to do this work by yourself, you must have thorough knoledge in electroncis, and must have all tools and ability to follow its schematic diagram. The most you need is patience. If you have these all, and want to do the repairwork by yoursef, inform me. I've the schematics of your tV, and all repair adjustments and proceedings. The power supply board and lamp ballast boards for Samsung (HL-T) series are shown here for your referecne. The lamp ballast board also may need to be checked.

I only fine 5 fuse where is the 6 fuse locate? Please help I found the 5 on the power board... is the 6 fuse somewhere else not with the power board?

The printer Board B1: you must shut it down by hitting the Options button and then selecting Function >Shut down > Shut down sytem>OK. Then power the machine off with the main switch. If the Customer has not been shutting off the machine properly and you get the please wait message you might try reloading system software first before replacing the hard drive.
Or = remove and reseat the printer board, if that doesn't work then you'll have to reformat the HDD unit and reload system software from a laptop. If the problem remains, the printer board may need to be replaced.

The Color Network Printer Board -B1 has a shut down function. It is for preventing corruption of the HDD. Be sure to turn off the main power switch after performing shutdown.
To properly shut down the Color Network Printer Board -B1:
1. Press the Option key on the control panel if the copier is in copier mode.
2. Make sure that the LCD reads Idle.
3. Select Functions on the LCD.
4. Select Shut Down from the Functions screen.
5. Select Shut Down System from the Shut Down screen.
6. The message 'It is now safe to power off the system' appears on the screen.
7. Power off the main power switch located on the lower right side of the copier.
* Note- After powering off the copier, wait at least five seconds before powering the copier back on.

How many times per second does the POWER led blink? (dont worry about the OPC).

1x per second (constant, steady blink) = bad inverter/lamps
2x per second = bad power supply
3x per second = bad main board

You can buy the parts online and fix if yourself!!