Samsung LE37M86 inverter failure (buzzing transformer+audio sample)

[Dannyx]

Good day folks. So I've been struggling to fix the inverter of this Samsung TV for almost a week now, but it seems it doesn't want to be repaired - I'd replace a component, only to have another one fail somewhere else, so I'd like to ask for some help/advice. It all started with 2 blown MOSFETs which drove the same transformer, so I replaced them, it worked fine for like 2 days, but then ANOTHER 2 FETs blew on two separate transformers this time (funnily enough, other than the two I had already replaced). I decided to push on and replace these ones as well, I did so, it worked for like 2 hours and this time a smaller 0.16A fuse blew, which had me quite worried, because I could not identify and shorted components, so I decided to just shunt that fuse and try again anyway: no smoke came out, however one of the transformers makes this pretty loud buzzing sound, as if arcing internally. Listen to the sound file in the archive I uploaded, at around 00:14. The beginning is just me plugging the damn thing in, switching on an MCB and waiting for it to turn on . It doesn't explain why the little fuse blew though, as the FETs draw their power through larger 3A fuses, while this 0.16A one is the only one of this kind on the whole board. Is it worth replacing the transformer, or will that lead to more components blowing ? Any experiments I can do ? I can provide pictures if need be.

[CapLeaker]

Re: Samsung LE37M86 inverter failure (buzzing transformer+audio sample)

That doesn't sound good. There is some HV arcing to GND.
With inverters I found was that most of the time I could get a whole replacement inverter cheaper or at least for the same money it cost me to order parts and fix the old one. Then I am still out time fixing the old one. Up to you, I guess...

[dick_barton]

Re: Samsung LE37M86 inverter failure (buzzing transformer+audio sample)

You may be able to see where it is arcing if you are in a dark room.

[Dannyx]

Re: Samsung LE37M86 inverter failure (buzzing transformer+audio sample)

You may be able to see where it is arcing if you are in a dark room.

Unless the arc is "hot" enough, I don't think it would glow though the matte-black casing of the HV transformer to be able to spot it. The protection circuit shuts it down quickly anyhow. I was thinking of swapping the transformer which I assume is faulty, with one from further away on the board, that way, I can definitely hear the noise a bit better.

[CapLeaker]

Re: Samsung LE37M86 inverter failure (buzzing transformer+audio sample)

did you measure it and compare it to the other transformers on that board?

[Dannyx]

Re: Samsung LE37M86 inverter failure (buzzing transformer+audio sample)

did you measure it and compare it to the other transformers on that board?

Yes I have done that, although only the secondaries were consistent in their resistance (around 5.2 kOhm if memory serves). The primaries gave too diverse readings to be able to set a baseline for what's good and what's bad, obviously some of those components on the board were affecting the reading. Although removing the transformers would sort out this issue, I'm not entirely sure it's the transformers to blame to begin with - could be a cracked lamp end, which would make it game-over.