There is evidence of some heat and one of the inverter transformers has been swapped already. I also resoldered several bad/broken connections. The voltage at pin 23 of the connector to the main board (INVERTER ON/OFF) jumps from 0V to 4.3V and back to zero at a rate of about 60hz. After about four or five cycles, the backlights shut off, but the PSU stays on.
I've worked on a set with a very similar PSU, BN44-00264A.
https://www.badcaps.net/forum/showthread.php?t=29580
I broke the screen in that one and traded the whole thing for RC parts so I don't have the board to swap in. However, I have the board that came out of it originally. It is missing the lowest transformer but has been reworked to still light the top twelve bulbs. The set powers on and stays lit but there is a dark band, as would be expected, at the bottom of the screen.
I found this video...
https://www.youtube.com/watch?v=PflyJ4H51Fg
...it looks like the burnt spot is likely due to a bulb or two going bad in the panel, which is what was happening in the other TV I worked on. Once I determine what is wrong with this PSU, I plan on fixing the bulb issue in this panel.
Looking at the PSU, the transformer tests exactly like the other three on the board. No shorted or open secondaries. I guess it's possible that the transformer is heating up quickly and causing the lights to power off at which point it quickly cools and the lights come back to life.
Would a bad transformer cause the INVERTER ON/OFF voltage to drop out though?
I've worked on a set with a very similar PSU, BN44-00264A.
https://www.badcaps.net/forum/showthread.php?t=29580
I broke the screen in that one and traded the whole thing for RC parts so I don't have the board to swap in. However, I have the board that came out of it originally. It is missing the lowest transformer but has been reworked to still light the top twelve bulbs. The set powers on and stays lit but there is a dark band, as would be expected, at the bottom of the screen.
I found this video...
https://www.youtube.com/watch?v=PflyJ4H51Fg
...it looks like the burnt spot is likely due to a bulb or two going bad in the panel, which is what was happening in the other TV I worked on. Once I determine what is wrong with this PSU, I plan on fixing the bulb issue in this panel.
Looking at the PSU, the transformer tests exactly like the other three on the board. No shorted or open secondaries. I guess it's possible that the transformer is heating up quickly and causing the lights to power off at which point it quickly cools and the lights come back to life.
Would a bad transformer cause the INVERTER ON/OFF voltage to drop out though?
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