The Power Supply. This circuit board is probably the most important board inside the TV, second only to the Main Board or perhaps, more accurately, it may be just as important. Any TV will need a power source in order for it to work. In fact, each of the other circuit boards need a power source in order for them to work. Put together, all of them need the Power Supply for each part to be doing their jobs. You can think of the Power Supply to be like the "heart" of the TV. While each of the boards fulfills a particular function on their own, they can't do their jobs without "blood" pumping through them, and not just any amount of "blood" but the correct amount. And that's what the Power Supply essentially is. And if, at any point, the Power Supply was not 'supplying' the correct amount of blood to each of the circuit boards, funny stuff will start happening to your TV. Maybe the screen turns on briefly before shutting down. Maybe the screen turns on, you may even see the logo briefly, but resets itself every minute or so, and the same cycle repeats itself over and over again. These are symptoms of a faulty Power Supply BUT! It could also be the case that one of the other circuit boards may be malfunctioning as well. Hard to say, since in either instances, the same sort of symptoms will occur. 

Let us try to better illustrate this with an example. If the Power Supply sends an electrical current to, say, the Backlight Inverter Board, but that board either 1) didn't receive the correct amount of current or 2) is faulty in some respect and hence could not hold the same current that was sent to it to be returned back to the Power Supply, the symptom that occurs here is that it "wants" to turn on but shuts down shortly after. What would be the source of the problem here? Would you deduce that it is a Power Supply issue? Or would you deduce that it is Backlight Inverter Board issue? How would you know? And the answer to that is too long and complicated to explain here. However, we will say that the answer lies in figuring out where the current (aka voltage) is falling short OR is exceeding what the circuit boards need to function properly. If too much current is going to a circuit board, you can sort of imagine what would happen. It's like overfilling a balloon with water. What happens when you overfill it? That's right. It pops. Similarly, something or a series of things will likely "blow" inside your TV when too much current is coursing through the TV. However, the nice thing about the modern day LCD TV (or LED TV) is that every TV will have some sort of "back up system" where if too much current is flowing through it, the TV will continue to function normally, for the most part, but will occasionally encounter problems. And for the average Joe or Jane, one won't notice it having any real 'major' problems besides deducing that perhaps the TV is old and that things break when they are old. The problem will just get worse over time eventually leading into complete failure, in which case the TV doesn't turn on or wants to turn but there's a whole list of symptoms that it exhibits while attempting to turn on.

Anyway, so you have your TV opened up and you want to locate that Power Supply. What do you look for? Well, the easiest way to figure that out is to find that one board that's the biggest one out of all of them and every which wire is connected to it or "flows back" to it. It may be covered by a steel cage so you'll have to remove that first to gain access to it. Remember, the Power Supply is the "heart" of the TV and every circuit board needs blood flowing through them in order for them to work. They take a variety of sizes depending on the size of your TV. They could be a square like this part: A1362549B or they could be a rectangular shape like this part: 1-474-202-11. They could be big and heavy or they could be thin and light. It just depends on the TV. 

Another way to figure out which board is the Power Supply is to look for the board with the most capacitors on it. And these capacities will generally be big and bulky like this LG Power Supply (that goes to a Plasma TV): EAY58316301. Do you see the big, brown circles wedged between two heatsinks? Those are capacitors. Capacitors could have a plastic seal like the brown ones or they could be "open" like the three silver top capacitors on the top far right corner of the same board. It's also common to find condensers, resistors, coils, and fuses on these boards. And those components take a variety of shapes and sizes as well. They could be standing up on a board or lying face down or sticking out sideways. There's just too many variations to adequately cover them all here. Remember in the last entry where we said that the Backlight Inverter Boards have transformers? Power Supplies have transformers too and they are often times a lot bigger and bulkier than the ones found on Backlight Inverters. Please refer to the previous entry for what transformers look like.

And that about sums up how to find the Power Supply inside an LCD TV (It's also applicable to LED TV's and Plasma TV's or really, any kind of flat panel TV).