Re: Problems with Samsung 740N monitors
agreed with all you said
Originally posted by eguevarae
My friend, glad you are back.
Well, you now gave some more info. Now you say that the CCFLs are working with other board, which mostly eliminates them from the equation.
As I've seen so far, there are many causes for either the blown/leaking caps or the fuse blowing.
The only recent case of a Samsung PSU/Inverter that blew a fuse in front of me (after I had changed it) is a 203B Board. It had bad lamps, they drew a lot of current, and blew the fuse. I replaced the fuse and it blew again. The screen only flashed for a moment (as when the inverter fails) and then it was off again. After the blown fuse (as a note, I had recapped it already), I replaced it by one slow blow as the one in your pics, but instead of attaching the 203B lamps, I attached a set of lamps from a 18" I have. They lit evenly and without problem or fuses blowing all over the place. Then I reattached the 203B lamps, and as soon as I turned on the PSU (this model has a switch. Very convenient...), the screen flashed, the fuse blown, and I was pissed off.
I took apart the lamps and they were loose or something (nearly broken), and the voltage arced to the reflection film on the inside of the rail that protect the lamps, and this short blew the fuse. In the end, the LCD itself was damaged, as I replaced he lamps only to find that the LCD has a vertical line in the middle. In this case, bad lamps blew the fuse.
In a not-Samsung case (cases, I might say), the problem was the use of bad quality caps, at a 85c temp rating, in a poorly ventilated area and with a design that left heat sources too close to the caps : Proview/KDS/Sylvania/MAG & others using Mirage Electronics PSUs. I have cases (I document every damn thing I do) of PSUs with bad caps, bad lamps and blown fuses. I have observed too that when the lamps are old, they take more time to fully start up, drawing much current in the process. maybe you didn't see it because, as you say, your CCFLs are good, but attach a set of pink-hued lamps, and you'll see that you easily break the 3.15A barrier. I guess that the fuse is there for cases like this among other things. And each case is different. Maybe in a controlled environment the PSU behaves well, but if the user has the unit in a poorly ventilated area working around the clock every day, the chances that something goes wrong (especially with the superb quality of the Elites & capXons found in many PSUs), ranging for intermittent failures to sudden death caused by blown fuses, are high.
Well, you now gave some more info. Now you say that the CCFLs are working with other board, which mostly eliminates them from the equation.
As I've seen so far, there are many causes for either the blown/leaking caps or the fuse blowing.
The only recent case of a Samsung PSU/Inverter that blew a fuse in front of me (after I had changed it) is a 203B Board. It had bad lamps, they drew a lot of current, and blew the fuse. I replaced the fuse and it blew again. The screen only flashed for a moment (as when the inverter fails) and then it was off again. After the blown fuse (as a note, I had recapped it already), I replaced it by one slow blow as the one in your pics, but instead of attaching the 203B lamps, I attached a set of lamps from a 18" I have. They lit evenly and without problem or fuses blowing all over the place. Then I reattached the 203B lamps, and as soon as I turned on the PSU (this model has a switch. Very convenient...), the screen flashed, the fuse blown, and I was pissed off.
I took apart the lamps and they were loose or something (nearly broken), and the voltage arced to the reflection film on the inside of the rail that protect the lamps, and this short blew the fuse. In the end, the LCD itself was damaged, as I replaced he lamps only to find that the LCD has a vertical line in the middle. In this case, bad lamps blew the fuse.
In a not-Samsung case (cases, I might say), the problem was the use of bad quality caps, at a 85c temp rating, in a poorly ventilated area and with a design that left heat sources too close to the caps : Proview/KDS/Sylvania/MAG & others using Mirage Electronics PSUs. I have cases (I document every damn thing I do) of PSUs with bad caps, bad lamps and blown fuses. I have observed too that when the lamps are old, they take more time to fully start up, drawing much current in the process. maybe you didn't see it because, as you say, your CCFLs are good, but attach a set of pink-hued lamps, and you'll see that you easily break the 3.15A barrier. I guess that the fuse is there for cases like this among other things. And each case is different. Maybe in a controlled environment the PSU behaves well, but if the user has the unit in a poorly ventilated area working around the clock every day, the chances that something goes wrong (especially with the superb quality of the Elites & capXons found in many PSUs), ranging for intermittent failures to sudden death caused by blown fuses, are high.
)
: why it shorted ?!?!?!?!?!? 
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