Samsung UE46F6320AY going On and Off

[dcia0015]

Hi everyone,

I came across your site while searching for help on this LED tv. The prime suspect when first checking this tv was the power supply. However on further investigation the power supply was ruled out. The set will switch on stby normally, when we try to power on using the jog button, the red LED starts blinking a small click of the relay is heard and a flash of the backlight will follow. The set will continue in this mode ad-infinitum. As said the voltages on the power supply connector are good and chacked using an oscilloscope for any ripple. The motherboard however shows no sign of life: The red light on the Digital Optical Out is off, when the ethernet cable is connected there is no indication of any communication with the switch. The supply on the LVDS board is absent (checked on the SMD fuse). Traced back to the motherboard, it is controlled by a transistor and when this was eneabled using the meter, the LVDS blue led's showed up. The tempreture of components on the motherboard do not show any sign of overheating.
Ultimately I downloaded the latest firmware from Samsung website and tried to update the firmware, however the only instructions found were how to update while the TV is showing some type of display, in my case the set is almost dead.
My doubt lies in that flash of the backlight, assuming there is something wrong with the backlight and being detected during that flash, is it possible that there is no life on the motherboard because of this.

Maybe someone with more experience can give me a hand.

Thanks

 

[DarkLinkX5]

how old is the tv?
Do any electrolytic capacitors look bulged at the top? they should be flat (not including the + shape indent on some). sometimes those go bad because of a supplier issue or someone ordering components with a short lifespan on accident to save money.
check all the smd electrolytic capacitors caps (if it has some) sometimes they leak too.
Sometimes they go bad sometimes they dont. you didn't mention checking them so i thought i would ask.

 

[dcia0015]

Two years or so, I checked the electrolytics they all show good ESR and those in doubt changed. The power supply does not have any SMD capacitors, on the motherboard there are. However I do not have a schematic of the motherboard to identify the supplies generated and the corrisponding electrolytics. I hate replacing electrolytics at random, especially on the motherboard which can easily be damaged with the heat of the soldering iron or hot-air.