POWER SUPPLY BN44-01056A Power fluctuation ON MAIN CAPACITOR

[bohaboha]

As long as you take the main board off the PSU and "force" the PSU on and all the voltages are correct, it is safe to say you got a main board problem. We don't know what the TV model number is, nor we know what the TV main board does or doesn't do (symptoms why you think the main board is bad). Also the voltages you talk about, we haven't got a clue what pins they correspond to.
Some pins for example the dim pin voltage depends on what the back lights are set to. The PSon and BLon pin should be very close or the same as STBY voltage. Dim, PSon, BLon comes from the main board and tells the PSU what to do. The only voltage originating by the PSU and sent to the main board is STBY.
Maybe the main board has a short somewhere and dragging the voltage down. Who knows. Too hard to tell if we don't see the whole picture or don't get told the whole story.
Maybe make a new thread in the TV section, since you got main board trouble.

thank you CapLeaker allow me to be more specifique if 5V is STB stated on PS legend but it only supplies 4.3V to Mainboard would Mainboard not be negatively affected or would it work anyway?
I'm talking about this PS we're dealing with here.
then on this Power Supply Legend there is no specified Current Value of ANA_DIM and other how to know the correct value?

[CapLeaker]

STBY sez 5V, but delivers 4.3V to the main board is fine. What does STBY do if the main board is disconnected? It is also enough voltage for the PSU to turn itself on (through a pull up resistor) when main board is disconnected.
The ANA DIM pin voltage depends on what the back light brightness was set to and comes from the main board. It could be anything for example 3.2V, 4.3V or 2.8V.
PSon and BLon voltage also comes from the main board. All it does is turn the PSU section responsible on or off. Back in the days Samsung didn't have the pull up resistor feature yet, so we were "forcing" the PSU on by taking a 1K ohm resistor and jumped STBY -> 1K resistor -> PSon, BLon and some Dim pins. There is a threshold (I'd like seeing at least 3V, and that depends on what TV brand). where too little voltage or no voltage from the main board provided to the PSU didn't turn the back lights on. To fix that quickly was to put a 1k resistor between PSon and BLon and called it a day, instead of getting a new main board.

[bohaboha]

STBY sez 5V, but delivers 4.3V to the main board is fine. What does STBY do if the main board is disconnected? It is also enough voltage for the PSU to turn itself on (through a pull up resistor) when main board is disconnected.
The ANA DIM pin voltage depends on what the back light brightness was set to and comes from the main board. It could be anything for example 3.2V, 4.3V or 2.8V.
PSon and BLon voltage also comes from the main board. All it does is turn the PSU section responsible on or off. Back in the days Samsung didn't have the pull up resistor feature yet, so we were "forcing" the PSU on by taking a 1K ohm resistor and jumped STBY -> 1K resistor -> PSon, BLon and some Dim pins. There is a threshold (I'd like seeing at least 3V, and that depends on what TV brand). where too little voltage or no voltage from the main board provided to the PSU didn't turn the back lights on. To fix that quickly was to put a 1k resistor between PSon and BLon and called it a day, instead of getting a new main board.

thank you