LE23r32b losing 24v and 12v
Good day folks. I'm having a small issue with a Sammy TV: the power supply loses its outputs when loaded...should I change F9222L ? That was quick, wasn't it ? 
Let's look at it in depth: the power supply is in the pics below. Couldn't find a complete schematic sadly. All I managed to find was THAT (see below). When I got it, it had two blown caps on the 24v line. Replaced them and it still wouldn't come on: the LED would turn on, the TV attempts to switch on then cuts out. Taking some measurements on and off the TV, I noticed the 24 and 12v outputs drop to around 3-4v when loaded (regardless of which one is loaded). By contrast, the 5VSB output AND primary cap remain perfectly stable at 5v and 380v respectively (although STBY is a bit high for my taste when not loaded - 6v, which I think is still passable though...the TL431 is probably on its way out). I tested the TV with an external 5/12v supply and it works, so the main board is not faulty or shorted. I'm leaning towards the F9222L being faulty, since it handles both those "high" outputs...not exactly cheap, so I don't really want to go for it until we've exhausted every other possibility.
I also thought of a a faulty TL431, which I happened to encounter a while back on a similar board, though the symptom was pretty much the opposite: the output would overshoot instead of undershoot and the TL431 read almost shorted on diode test with my meter. The one found here seems fine, which is PC803S btw. It monitors the 12v bus apparently. There's 4 optocouplers on the board and although they're not present in the schematic I found (I reckon it's missing a page or two), I believe they're for PS_ON, 5V feedback, 12v feedback and a fourth one which I can't think what it's for, other than maybe 24v feedback, which doesn't really makes sense since they're both ran off the same transformer, so only one would suffice...any thoughts ? Wrong order on the pictures there, I know, but NVM Cheers and thanks.
Let's look at it in depth: the power supply is in the pics below. Couldn't find a complete schematic sadly. All I managed to find was THAT (see below). When I got it, it had two blown caps on the 24v line. Replaced them and it still wouldn't come on: the LED would turn on, the TV attempts to switch on then cuts out. Taking some measurements on and off the TV, I noticed the 24 and 12v outputs drop to around 3-4v when loaded (regardless of which one is loaded). By contrast, the 5VSB output AND primary cap remain perfectly stable at 5v and 380v respectively (although STBY is a bit high for my taste when not loaded - 6v, which I think is still passable though...the TL431 is probably on its way out). I tested the TV with an external 5/12v supply and it works, so the main board is not faulty or shorted. I'm leaning towards the F9222L being faulty, since it handles both those "high" outputs...not exactly cheap, so I don't really want to go for it until we've exhausted every other possibility.
I also thought of a a faulty TL431, which I happened to encounter a while back on a similar board, though the symptom was pretty much the opposite: the output would overshoot instead of undershoot and the TL431 read almost shorted on diode test with my meter. The one found here seems fine, which is PC803S btw. It monitors the 12v bus apparently. There's 4 optocouplers on the board and although they're not present in the schematic I found (I reckon it's missing a page or two), I believe they're for PS_ON, 5V feedback, 12v feedback and a fourth one which I can't think what it's for, other than maybe 24v feedback, which doesn't really makes sense since they're both ran off the same transformer, so only one would suffice...any thoughts ? Wrong order on the pictures there, I know, but NVM
Cheers and thanks.
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