Hi guys, I have a problem with a blown power supply from a Samsung monitor. Specifically the power supply is a bn44-00750A. Basically bought a broken monitor mainly for myself to try and fix it and also learn in the process. Myself I am more of IC design engineer, but I have worked with pcb’s and components in my student life and I feel confident doing the repairs, but I am not sure exactly what to look for as I have no experience with power supplies (but hey, never too late to learn).
And after doing some tests myself I found that:
1. First things first, do we have expected 13V output voltage? Nope
2. Ok then let’s check the components: Fuse is gone
3. Bridge rectifier is gone-> the bridge simply outputs the 220 ac voltage. plus all pins are shorted.
4. There was a 0.10ohm resistor that was clearly burned further down the path from the rectifier
5. I am pretty sure that some of smd transistors on the hot side are also burned. (in red circle what looks like a transistor, all pins are shorted, but the ones next to it seems fine)
6. The main capacitor is not shorted, but I cannot test it properly without taking it out, since it is glued like hell to the pcb.
7. I have checked all diodes and they are ok.
In the pictures I have circled in red what I think it is still broken, and in blue where the resistor, bridge rectifier and the transistor were. I have taken progressively zoomed in pictures to have a clear view of the board. I focused mostly on the hot side of the board.
Now before going into the details, I would like to know if there is a possibility that the cold side was also affected and if (I hope not) the main board of the monitor could also be damaged. I personally think not since I do not read any voltage at the output.
Also how can I find a good replacements for some components (for example the small smd transistors). On the internet I couldn’t find any schematic and specs of this board.
I am looking if there is anybody who could give some pointers as to where exactly to look for more damage and if it is worth trying to fix. Thanks!
And after doing some tests myself I found that:
1. First things first, do we have expected 13V output voltage? Nope
2. Ok then let’s check the components: Fuse is gone
3. Bridge rectifier is gone-> the bridge simply outputs the 220 ac voltage. plus all pins are shorted.
4. There was a 0.10ohm resistor that was clearly burned further down the path from the rectifier
5. I am pretty sure that some of smd transistors on the hot side are also burned. (in red circle what looks like a transistor, all pins are shorted, but the ones next to it seems fine)
6. The main capacitor is not shorted, but I cannot test it properly without taking it out, since it is glued like hell to the pcb.
7. I have checked all diodes and they are ok.
In the pictures I have circled in red what I think it is still broken, and in blue where the resistor, bridge rectifier and the transistor were. I have taken progressively zoomed in pictures to have a clear view of the board. I focused mostly on the hot side of the board.
Now before going into the details, I would like to know if there is a possibility that the cold side was also affected and if (I hope not) the main board of the monitor could also be damaged. I personally think not since I do not read any voltage at the output.
Also how can I find a good replacements for some components (for example the small smd transistors). On the internet I couldn’t find any schematic and specs of this board.
I am looking if there is anybody who could give some pointers as to where exactly to look for more damage and if it is worth trying to fix. Thanks!