I have a 2013 RCA model LED55C55R120Q. It stopped working. Behind the back panel it was covered with a dripping liquid everywhere that didn't dry. Any clue what this is??!

If it was thick and clear, it could be the fluid from electrolytic capacitors. These are usually used in electronics to filter the AC hum from DC power supplies so that you don't hear it in the speakers or see it as wavy lines in the picture. These capacitors act similar to batteries in that they charge but they discharge in an instant. Think of a photo flash gun. This is a capacitor in action. This fluid is messy but, unlike a battery, is NOT corrosive. If your stand is made from cheap pressed wood and the liquid was on it for a while, it may soak in and blister it but then, so would water. These capacitors have 2 values and a polarity. One value will be marked as "uF" or micro farads. This is how much energy it will store. The other is the operating voltage or the maximum voltage that you can feed into it without damage. The polarity is like a battery. You connect it right, it works. You connect it wrong, POP!!! This was not your case though. If it were connected wrong at the factory, they would have either popped during testing or shortly after you turned it on for the first time. The problem with these concerns money. If that were a government spec TV, it would last forever. For the consumer market, companies go cheaper and cheaper until they use just the bare minimum to get it working and out the door. If you are building a good DC power supply, the rule of thumb is to use filter capacitors that are rated at least 3 times the output voltage of the supply. If your supply puts out 12 volts, your "caps" should be rated around 40 volts minimum for reasons that you may not understand but trust me. I'm just pulling numbers out of the air here but if your TV's power supply put out say 30 volts. The filter "caps" should be rated for 90 volts. They could get away with 45 or 50 volts but there's a reason for the rule of thumb. If they are rated at 200 uF and that's what you have, that's of no consequence and fine. It's the voltage rating that's important. NOW, if you are a tinkerer, BE SURE that the TV is unplugged BEFORE you open it up. After you get it open, look around where the power cord comes into the case. There should be some circuitry where the power cord connects. You will be looking for some small aluminum cans that can be about any size but if it was a substantial amount leaking out of the set, it was probably a good size "cap". Look for one or possibly several about the size of a regular prescription medicine bottle with colored plastic shrink wrap around each individual one. There will be writing on them with a brand name that probably WON'T match the brand of TV. There will also be numbers on them like 100 uF 50 VOLTS for example but they could be anything. They also will have either a + and - sign or sometimes a string of just - signs both denoting polarity. The key to look for is the "uF" and "VOLTS". the "u" in uF may also look like the symbol for micron with a little tail on either side of the "u". My keyboard doesn't do Greek symbology. If these are blown, they may range to looking like their top is bulged out slightly all the way to something that looks like waxed paper and aluminum foil confetti all over everything and the metal cans offset at an angle from the circuit board or even completely loose and rolling around on the bottom. These won't explode with much force as they are only contained on the bottom with a rubber disk. If it was these that blew, it probably shorted the supply. If you are lucky, it just blew the fuse that is supposed to be in the circuit. It is probably a glass fuse like they used to use in cars. Sometimes these are specialized "slo blo" fuses and should be replaced with EXACTLY the same value. NOT a piece of wire or wrapped in aluminum foil if you value yours and your families lives. If they went cheap on filter caps, I would worry what else they went cheap on. Good luck.