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I have a KDL-55EX620 that I've owned for a little more than 2 years. I work from home and the TV is on the vast majority of the time, so it gets a LOT of use. Several days ago the TV just abruptly turned off while in use, and the power light started blinking red twice (blink, blink, pause, repeat). Did some Googling and from what I can find it indicates a faulty power supply unit, which wouldn't surprise me at all given how much use it gets.


I ordered a replacement APS-299(CH) PSU board which was used but fully tested from a very reputable source for used LCD components, but when I swap out the board the TV is just completely dead, no red light at all and it doesn't turn on. Although I was confident that the board was good, I ordered a second used and fully tested board from a different reputable seller of used used LCD components, and again I get the same results when I turn it on, no red light at all. When I re-install my original PSU I still get the two blinking red lights. The odds of both these boards being totally dead are ridiculously low given the ratings and reputations of these sellers, and both of them state that the units were fully tested. These are businesses for both sellers, with thousands of components sold, it's not like either of these boards were ordered from someone who just happened to have a spare in his closet from an old broken TV.


When I tried to find the replacement PSUs for my TV I noticed it was very hard to find the original PSU #147430311. Turns out it was discontinued and replaced by #147433011, which ships in the more recent models of this TV line. I confirmed with multiple sources that the boards are supposed to be 100% interchangeable. The first replacement board I ordered was the newer part number since it was so hard to find the original PN, and when that one wouldn't work, the second one I ordered was the exact part number from my TV, taken directly out of another 55EX620 that had a cracked LCD screen.


If anybody who's very knowledgeable about these components, the trouble codes, and repairing them wants to chime in, I would greatly appreciate your input. I've watched how-to videos for the replacement of these boards and it's completely plug and play, with no need to reset anything according to the tutorials. At this point my only recourse is to spend even more money and time have someone come out to repair it, but given how easy it is to replace these boards it just seems like an unnecessary waste of money to have somebody service it, when I'm fairly certain they're just going to swap a board as well.


TIA
 

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I hope is not too late!!

I think that u may have a problem on the dps-78 board. You must check R6540 on the original power supply board. it probally originally blows up on your first board and then when u did replace it u have the main fuse blown as soon as u power on the machine.

U have to check Q6602 and Q6603 on the dps-78 board that it will be probably the thing that cause all your power supply to blow
 
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