With this symptom, it is impossible to tell what the exact "Cause" of this symptom is. The LED's do not tell us what is wrong, sometimes it may indicate the "Area" in your case it is the X board. BUT that's NOT where the "Fault is" that's just the part that is affected. T What is happening is that you have a fault in the set, that is potentially very bad, and the Power Supply senses this and attempts to shut it down, now when it shuts down, the fault clears momentarily, and so the PSU, again tries to power up, sense the fault and tries to shut down again, we call this a Hic-upping Power Supply, and is often the symptom of a much larger underling problem. These days unlike the "Old" analogue days it just isn't realistically possible to fix anything but the most basic of problems with today's sophisticated units. This is quite apart from the Safety aspect, any unit that can cause a firs or have an explosion, or both, is NOT to be treated lightly, and and the repairer, of the unit is legally responsible, another thing to think about. Also, one must have tools, a Multimeter, a soldering iron, a deslodering iron, an oscilloscope, a signal tracer, tools, and most important of all, a Service Manual, without which, there is no way to even begin to understand and fix it, and more importantly Program it, AFTER it has been fixed. As these days a TV, is a PC, a Tuner, and an HDTV Monitor, and more, all in one. in the "old" days TV"s were more, rudimentary, and built to last for 20 years, and a "Parts" supply was set aside. They usually used to fail for only a few reasons, and they while still difficult, were less difficult to repair. Electrical knowledge was transferable, and they could be and would respond to, This-is-the-symptom-This-us-the-Fix, But that no longer applies, as now, it can be a Fault on I squared Bus, or "Sensor" failure, or it simple may have "Crashed" just like a PC, It could be a Diode go bad, and that will stop the whole thing. You see, in the day, the sets were Very "Fault Tolerant" because they were Analogue, and a faulty, component, or more sometimes, the set would always display something usually, and when they didn't it was one of only a few things, sure there are always the horrid ones, and there are plenty of those, but all in all it was quite easy. But with Digital Electronics, it either goes, or it doesn't, there are usually few half measures. I mean that's the definition of logic either going or not. So it can take very little to completely paralyze a set, and generally give the only symptom, it can, by not working, usually No picture, or the like. So you, see the list is endless almost for any given SYMPTOM, as that is what is being seen, not the cause, as I keep going on about. Also any fault, usually involves the Power Supply, it is either the cause, the cause of the damage, or it is damaged. or ALL of them. Then after you have done the electronic repairs, you then must program the set to work, and align, and set up in general, any one of those settings missed or done wrong, back to square one. So, it is nearly always my professional opinion that one should always get a "Quote" form the manufacturers recommended service center, I cannot stress how important that last point is. It is even worth the cost of shipping. you see an authorised service agent, will have trained staff, trained on their brand, also they have first hand access to parts, original parts. This will actually save you money and ensure you can actually get it back fixed. Of course asking for a "Quote" also gives on the option of repair or replace. Often my clients,do not go through with repair, unless it is moderate, but in some of the more costly jobs they see it, as do i, that a replacement, with a warranty, is a better option. As an aside here, one could then tear the TV down, and sell the Known Good bits. You'd be surprised who needs parts, i myself often must by from third party sources to effect a repair. So money could be recouped, somewhat,and help out someone else.Service manual below.
http://elektrotanya.com/panasonic_th-50pz85u_ch_gpf11du.pdf/download.htmlIF you wish to try to fix it yourself, and I do not recommend it. FIRST, you Must get a service manual, then you need, equipment, an Oscilloscope is a MUST HAVE. Also a Multimeter, and soldering iron, a DE-soldering station, an anti-static wrist strap, (Any TV is extremely static sensitive). Now FIRST you must make sure the Power supply is 100% as if this is NOT then nothing else can be. Also there are safety considerations, any unit that can cause a Fire or Explosion, or both, needs to be attended to with the utmost care. As if it isn't done correctly, a catastrophe is indeed possible, Faulty sets can cause a fire, and a fire in the middle of the night, I believe is not good. And any person that has attended that set, will be held to account. Now with that understanding, I guess proceed if you wish.Troubleshooting say if it is shutting down, after a certain 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. Now just replacing boards will most likely just end up with more faulty, boards, as related you MUST ensure that you have the cause of the event, before we change anything. I have seen so called, "Techs" replace every board, and virtually every component, and that STILL didn't fix it, because the "Fault, or Cause" lay elsewhere, and had not be repaired FIRST, you see that FIRST STEP, like everything in life, is, CRITICAL.
