Hi everyone, sorry if I open a new thread on this power supply board, but after reading the present ones I was unable to solve the problem. A few days ago I turned on the monitor and hear a small bang, the monitor does not turn on and the blue LED flashes.
I disassemble the monitor and try to understand what the problem is with the power supply board, I immediately notice the RM801 (0.22ohm) resistor burnt. I replace it and try to turn it back on, of course it burns again, I put a new one and check with my digital multimeter the 2 fet QM802 and QM803 that are burnt, I replace them and, for safety I also replace the capacitors CM851, CM852, CB853 and also CM812 ( the blue 12nf 630V capacitor) also remove the brown glue from the board. I try to reassemble the board and turn on the monitor, this time nothing burns, the blue LED is on and does not flash but the monitor does not work. I disassemble the power supply board again and test the voltages 5.3v and 24v with a 3.3k resistance between S_B and PSON. Instead of 5.3v I have 0.45v and instead of 24v I have 0.05v. On the large central 82mf capacitor I have a voltage of 320V in standby and 390V in operation. Looking at the board from both sides I don't notice any other burnt components.
I attach 2 pics of the PSU, I hope you can help me solve.
Thanks
Francesco
I disassemble the monitor and try to understand what the problem is with the power supply board, I immediately notice the RM801 (0.22ohm) resistor burnt. I replace it and try to turn it back on, of course it burns again, I put a new one and check with my digital multimeter the 2 fet QM802 and QM803 that are burnt, I replace them and, for safety I also replace the capacitors CM851, CM852, CB853 and also CM812 ( the blue 12nf 630V capacitor) also remove the brown glue from the board. I try to reassemble the board and turn on the monitor, this time nothing burns, the blue LED is on and does not flash but the monitor does not work. I disassemble the power supply board again and test the voltages 5.3v and 24v with a 3.3k resistance between S_B and PSON. Instead of 5.3v I have 0.45v and instead of 24v I have 0.05v. On the large central 82mf capacitor I have a voltage of 320V in standby and 390V in operation. Looking at the board from both sides I don't notice any other burnt components.
I attach 2 pics of the PSU, I hope you can help me solve.
Thanks
Francesco
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