TV failed again -- this time an inverter board....
roughly nine months have passed since I started this thread, but after initial success fixing the TV by replacing capacitors, I have had it fail two more times, so I thought I would post an update.
When the first repeat-failure happened, I inspected the power supply board, and could see no sign of problems with the capacitors that I had previously replaced. But I replaced them again anyway, and still the TV wouldn't start. So I ordered a brand new power supply board, and it worked first time. So I figured my repaired power supply board must have had some other hidden problem. I stuffed it in a closet.
A couple of months passed, and then the TV failed again, with exactly the same symptoms. So I ordered a new power supply board again, but this time, the new board didn't help. So I started to hunt around for another cause of the problem, and zeroed in on the inverter boards, of which there are four. Every time I turned on the TV, there was a buzzing sound for a few seconds, and by listening closely with the back off the TV I was able to determine that the buzz was coming from the lower right board, part INV52B24A (RL). Then I had a hunch -- we've probably all seen fluorescent lights have a tough time starting when they are cold. Well it seemed to me like the inverter was trying to start the fluorescent backlight and not quite getting it going. So following my crazy hunch I grabbed a hair dryer and started to heat up the entire area around the inverter boards, thinking that if I could get the fluorescent tubes warm, they might start up. Crazy? Well, it worked! After maybe two minutes of heating, the TV started up normally. The I powered down and left the TV off overnight. The next morning, it wouldn't start up again. So again, I grabbed the hair dryer and started heating, and again, it worked after a few minutes. Interestingly though, when the TV did start, there was still quite a bit of buzzing coming from the RL inverter board, but not any of the others. Then I got really close to the board and looked at all the transformers, and was amazed to see across one of the transformer casings, exactly where the buzz was coming from, what appeared to be a light scorch mark and a tiny crack. Could this be the problem? I decided to try to replace that board, and quickly found that this part doesn't appear to be sold by Samsung as a separate part, however I found a used board on "ShopJimmy" and decided to give it a shot. Board arrived a few days later, and upon installation, the TV immediately worked, with no hair dryer, and no buzz whatsoever. I turned it off for a couple of days to make sure it was completely cold, and it powered back up without problem. Then I decided to swap out the new power supply board with my original, repaired power supply board, and that worked too.
The TV has now worked fine for two weeks with the new inverter board. It's hard to know how the the power supply capacitor problem and the inverter problem are linked... maybe the original capacitor failure caused damage to the inverter transformer. Or maybe they are completely unrelated failures that coincidentally had the same symptoms. In any event, the TV works again, at least for now.
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