Hello guys, from a couple of weeks now, I have been trying to fix my SONY KDL-40BX440, but failing miserably.
The TV have been slowly degrading for a year now, it used to turn off/lose picture and needed a few tries to turn on. It was working fine for a month after I replaced one of its power N-FETs (Q800) and its electrolytic caps, but now it won't turn on at all. The standby LED flashes 2 times ("Main Power Over Voltage Protection") and there is only standby voltage (3V3). The power board is DPS-166DP (the closest schematic that I found is of DPS-165GP).
This time 2 of its N-FETs were blown (Q800 and Q901), but replacing them didn't fix it. Component side ceramic caps, resistors, low voltage P-FETs, rest of high voltage N-FETs, diodes and diode bridge are fine. The transformer's windings are not shorted (this much I can tell with my basic knowledge of transformers). What seems suspicious to me is that the secondaries of T901 are shorted.
I haven't tested the transistors and ICs on the bottom yet, I thought it would be wiser to ask first.
At this point I really want to know what the problem is, any help is much appreciated.
https://tel-spb.ru/remont-tv-lcd/sony-kdl-40bx440
The TV have been slowly degrading for a year now, it used to turn off/lose picture and needed a few tries to turn on. It was working fine for a month after I replaced one of its power N-FETs (Q800) and its electrolytic caps, but now it won't turn on at all. The standby LED flashes 2 times ("Main Power Over Voltage Protection") and there is only standby voltage (3V3). The power board is DPS-166DP (the closest schematic that I found is of DPS-165GP).
This time 2 of its N-FETs were blown (Q800 and Q901), but replacing them didn't fix it. Component side ceramic caps, resistors, low voltage P-FETs, rest of high voltage N-FETs, diodes and diode bridge are fine. The transformer's windings are not shorted (this much I can tell with my basic knowledge of transformers). What seems suspicious to me is that the secondaries of T901 are shorted.
I haven't tested the transistors and ICs on the bottom yet, I thought it would be wiser to ask first.
At this point I really want to know what the problem is, any help is much appreciated.
https://tel-spb.ru/remont-tv-lcd/sony-kdl-40bx440
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