I have a LG 37lc2d and it suddenly turn off and wont come back on, the stand by lights doesnt turn on either. i was wondering if its just the power supply? or how can i troubleshoot this my self to see whats wrong with it.

There is a fuse on the power supply close to where the A/C is connected to the board. If the fuse is blown, look at the board and see if there are any burned components and or swollen capacitors. If there are bad components, I would suggest getting a new board.
If the board looks OK, disconnect the connectors from the board but leave in the A/C connector (this way you can isolate the power supply board), replace the fuse, and power up the TV.
If the fuse pops after the power is applied to the unit, then the power supply is bad.
If the fuse is still good, then power off the TV, connect on the main board’s connections, and power up the TV.
If the fuse is still good, then power off the TV, connect the inverters, and power up the TV.
If the fuse blows now, then the inverters and or the panel are bad.
A working power supply will create 5vdc for the main board’s stand by source voltage. This can be found on the power supply at the main board’s connector and it is labeled in black text.
I hope this information helps you.
Good Luck.