Hi there, the green light upon startup means the circuit boards are powering up. At some point ( a bad capacitor in your case) the system "runs" into a bad component ( the capacitor) and this faulty component will shut the system down ( for safety reasons the tv has a built in device that trips the circuit when a problem is encountered), this in turn shuts down "the power-up" cycle and the unit shuts off and displays the red light again....You will need to call a professional to have the circuitboards checked out. You can, if you wish, open the unit and use my guide to help you locate and diagnose the most common problem with tv's having the symptoms you've mentioned....The caps (capacitors) in the powerboard are going out. This is a very common problem in all class and price ranges of modern lcd and plasma tv's/ monitor's. I don't know if this problem has been like this for awhile or it just started, but either way, if the tv takes an abnormal amount of time to "warm" up then it most likely will go out all the way sometime in the (near) future. If you have a tiny bit of will and knowledge ypou can open the unit and get to the print board. Examine this for "popped" capacitors, they will have a buldging top instead of a flat one. Im gonna try to include a pic of them here, if i can get it this time, I've tried bfore lol. But you can google image a "popped" or "bad" capacitor and you would be able, with ease, to diagnose if you have any of these. Usually only one or two. Radioshack sells capacitors (couple anyway) for $1.59 each. MAKE SURE the replacement is of the SAME voltage or HIGHER, or you will be right back replacing those 2. Every capacitor has a negative pole marked with an (-) on the side of the capacitor(by one of the "legs", always puit the negative (-) "leg" of the new capacitor in the same hole in the printboard as where the previous negative (-) "leg" of the capacitor was ( a capacitor with the negative and positive "legs" put in backwards will result in the new piece "popping" as sson as you turn it on!!) make sure the "uf" rating (for example the most common popped capacitor is the 1000 uf) is the same as the one you are replacing. I needed 1000 uf, 105 c and 26v (volt) ratings for the 1 capacitor I needed to replace to fix my LG 19" lcd panel monitor I found by the trash that the light came on off, but it didn't come on. I replaced that capacitor with ; 1000uf, 85 c and 36 v (volts0...It works fine eventhough the volts and the temperature rating (36v and 85c) was not the same as the (26v(volt) and 105c ) capacitor I removed !! Further, I've replaced capacitors that had the celcius rating of 105 with the only ones Radioshack had, namely 85 c(celsius) they have been working great, but I'm not sure about any effect, nor have I heard or read (yet?) about that making an urgent difference. Many threads that I've read people have done the same, so we should be ok (my stuff has been running good for a while longer then most brand new ones!.............(all these ratings ; 'uf ' and 'c' etc are on the side of the capacitor you are replacing and on the side of the ones you are replacing them with)...For all this all you need is the cheapest solder gun u can find (I bought one for $7.99 at Radioshack), a camera (to take pictures as you go to remember how to reassemble the unit) and, once you have your materials, 20 minutes to replace 2 or 3 capacitors and you are good to go...Most monitors and tvs (lcd/plasma) I've seen you have to lay flat on the ground/bed/blanket etc, to work on (screen side down). Usually there are 2 or 3 screws (or a few more) to remove, then you will have to carefully (its comes off easily most times)insert a flat screwdriver inbetween the casing and gently pry it up as you go around the whole frame. Sometimes you have to remove the little washer arouind the cable input orso, just be gentle and you cant go wrong. Once insidet here will be a box with wires running to the sides etc...unplug, gently, these wires and open the box. Inside you will find 2 or 3 circuitboards, check them all for "popped" capacitors, replace, reassemble and plug it in....Have fun becoming an overnight tv mechanic lol! If this helped you any (or not) then please rate...Also I am very interested in your progress with this issue.
