I got a Sony Bravia KDL-40WL135. Blank screen. There's two LED lights: red standby and green power light. When I turn on the TV, green led comes on, then after about 30 seconds red led blinks once, then green resumes. The green led stays solid. I think that's a SONY error code, I tried to look it up but can't find anything useful. I have replaced the power supply, AU board, backlight inverter, logical board, and the second power supply board. Any suggestions? I haven't checked the t-con board

Http://www.smpcshop.com/KDL-40WL135-KDL-46WL135-p-8895.html
Above is a link for a service manual.

Hi, well I applaud you for starting in the right place, The power supply, as, if, that isn't right nothing else can be. But you simply cannot do anything without a Service Manual. In this it has everything one needs to repair the set. OK if it is shutting down, after that amount of time, of working and then faulting, then it is most definitely a "Thermal" problem, the way we "Find" problems such as this is "Freeze Spray" you use this on each component that is suspected of being the "Culprit" and you will soon,find that errant component. Now also not every fault is a Capacitor, I see many, many people that think, that Capacitors are always the "Culprit" now while that may be true in a few cases, a faulty Electrolytic Cap, or ordinary, Cap goes faulty, this is only a SYMPTOM, something has damaged those caps causing them to "Fail". One MUST always find the root "Cause", otherwise if you just treat, the SYMPTOM, the "Cause" will just make the "Symptom" come back, in short order, as the prime cause still, hasn't been fixed., Now Capacitors hate AC ripple, or Over Voltage. Thats it. Oh.. and Heat, if these Capacitors, are too close to a Heat Source, then thats a prime cause of failure. Resistors, hardly ever go faulty,and if they do, it is generally obvious. However it doesn't hurt to check values with our Multimeter. Remember though resistors are made, with up to 20% tolerance from stated value, as such, are not too critical, unless in Timing circuits etc. Always check, the Values, of resistors, as with any other component, with the power OFF. Now Diodes especially "Zener Diode", are another thing to check, those and ordinary "Signal Diode" should always be suspect. next we have Transistors and IC's. The Transistors MUST ALL be checked to see if they have a good, "Junction" this is done, with our meter set to "Diode Test" and usually are about 0.6 to 0.7. With IC's you must check, voltage levels, or Logic Levels, going in and out, have a look at the circuit diagram, and it will tell you what they should be. It is a good idea to always measure the Power Supply voltages, see if a "Rail" is Low, that will be because some component has gone somewhat or all short circuit, to Earth, now, if the "Rail" is Higher, suspect an "Open Circuit" component, like a Diode, or Transistor. The voltages expressed in the manual are spot on, ANY variation MUST be investigated. I have been doing all this for over 30 years now, and I do indeed wish, we could have a set of "Symptoms" and be ables to say.. "Oh that;s the so-in-so and replace this" however unfortunately this although does happen, most "Symptoms" can have literally tens, of "Causes" all often "Interlinked" One simply has to do a methodical troubleshooting procedure, and always think, "are my Voltages Correct" as this is how, you Fix the problem, by making them so. Keep up the good work. If that link above doesn't furnish a Service manual, it is imperative you get one, even if you must pay for it. It will pay for itself in about 2 mins.
Gee it seems that you have replaced just about the entire "Guts" of the set, in the industry we call this the "Shot gun" method, however it seldom works in reality. One really needs to isolate the Cause, of the "Fault" and repair that and also any damage done by that. As if one doesn't remove the "Cause" it will simply fault again when the "New" bit is connected up. One needs to get the unit going section by section, testing and proving the prior section before connecting up to the next, which also must be tested to make sure that what you are going to connect will NOT damage what you are connecting it to.
Also unfortunately, these LED's Blinks, are NOT an error code in actual fact.
What you need to do is use the service manual, and follow through the troubleshooting steps, to isolate and hopefully repair your problem.
Basically it is all about voltages and if they are correct, a Higher voltage than stated usually means a component is Open circuit or a very high resistance, whereas a Lower than stated voltage usually indicates a Short Circuit, or low value resistance component, is "Faulty". These are all in the SM, as are the waveforms that must be checked, it is indeed very difficult to repair electronics these days without specialised equipment and even though I have over 30 years experience i find it difficult, so good luck.