There's a thread on the site titled "Sharp Aquos 80" TV ~ Model # LC-80LE844U ~ Not operational", detailing the process of the most common problem affecting power supply board PSD-0888D.
For the sake of bringing something of value I'd also add (even though it probably belongs in the thread itself) that what's described there is one of the TWO possible variants of the failure - blown IC, blown fusable resistor 2.2 Ohm or 2 Ohm.
The other is an internally failed, but not shorted IC, resulting in resistor that's still intact, but the board spontaneously losing power after anywhere from a few seconds to a few minutes of operation.
In other words, when in doubt, always replace the IC. (in fact I personally simply always replace the IC, whether doubting or not - it's fast, easy, cheap and insures client won't come back during warranty because of an aged and finally broken IC...that's my general philosophy and approach to all common failures).
This post is about a problem that gives almost the same failure symptom, but definitely has a different origin, which, for the life of me, I can't figure out.
What is happening is the board starts, the relay clicks, the PFC raises momentarily to somewhere above 300V - like 310V or so, but not 380V-400V it should go, at least not by the Fluke, the secondary DCs all show up as they should and then, practically immediately, the PFC starts going down, apparently turned off.
The PFC driver is UCC28061 and it is definitely not the issue.
It's been a while since I last spent a night chasing this before giving up, but today yet another one of those board showed up with the same issue.
Unfortunately I can't find my previous notes, but I do remember I found the following: If I cut a certain track of an IC in the surroundings of the PFC driver the PFC stayed on and produced 396V as it should.
I got to this track while chasing the signal causing the shutdown, but that's what I remember from it...and the suspicion it may be some of the high voltage dividing resistors to have gone off and cause all this.
This is one of those nasty issues where things aren't exactly failed so you can just track down the short and take care of it (not that those can't have nasty side issues to kill your sleep, but it's less often).
It's luckily not a problem where you have to wait an hour for a spontaneous shutdown either - it's quite persistent and reproducible.
Yet in several multi-hour attempts over the pat few months I've failed to nail it.
Any help will be appreciated and I wouldn't at all mind paying for the knowledge...I am by no means novice to electronic repairs, but I don't quite consider myself professional either, even though most people probably would consider me such.
It's just that I know real professionals and I know I am not their level...and likely never will be.
I am just someone who usually finds solutions to problems and this one I so far can't.
TIA,
Bobby
For the sake of bringing something of value I'd also add (even though it probably belongs in the thread itself) that what's described there is one of the TWO possible variants of the failure - blown IC, blown fusable resistor 2.2 Ohm or 2 Ohm.
The other is an internally failed, but not shorted IC, resulting in resistor that's still intact, but the board spontaneously losing power after anywhere from a few seconds to a few minutes of operation.
In other words, when in doubt, always replace the IC. (in fact I personally simply always replace the IC, whether doubting or not - it's fast, easy, cheap and insures client won't come back during warranty because of an aged and finally broken IC...that's my general philosophy and approach to all common failures).
This post is about a problem that gives almost the same failure symptom, but definitely has a different origin, which, for the life of me, I can't figure out.
What is happening is the board starts, the relay clicks, the PFC raises momentarily to somewhere above 300V - like 310V or so, but not 380V-400V it should go, at least not by the Fluke, the secondary DCs all show up as they should and then, practically immediately, the PFC starts going down, apparently turned off.
The PFC driver is UCC28061 and it is definitely not the issue.
It's been a while since I last spent a night chasing this before giving up, but today yet another one of those board showed up with the same issue.
Unfortunately I can't find my previous notes, but I do remember I found the following: If I cut a certain track of an IC in the surroundings of the PFC driver the PFC stayed on and produced 396V as it should.
I got to this track while chasing the signal causing the shutdown, but that's what I remember from it...and the suspicion it may be some of the high voltage dividing resistors to have gone off and cause all this.
This is one of those nasty issues where things aren't exactly failed so you can just track down the short and take care of it (not that those can't have nasty side issues to kill your sleep, but it's less often).
It's luckily not a problem where you have to wait an hour for a spontaneous shutdown either - it's quite persistent and reproducible.
Yet in several multi-hour attempts over the pat few months I've failed to nail it.
Any help will be appreciated and I wouldn't at all mind paying for the knowledge...I am by no means novice to electronic repairs, but I don't quite consider myself professional either, even though most people probably would consider me such.
It's just that I know real professionals and I know I am not their level...and likely never will be.
I am just someone who usually finds solutions to problems and this one I so far can't.
TIA,
Bobby
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