Hello,
I'm hoping to get some help figuring out how to troubleshoot this power supply board. The television is a Samsung UN75J6300AFXZA, version no. UH03. The power supply board has two model numbers on it, L75S1 and BN44-00723C. As far as experience level, I'm familiar with recapping boards in terms of safely going through the soldering motions, choosing suitable replacement parts, and so forth, but as far as understanding the various functions of each part of these TV power supply boards, I am a rank beginner.
When I plug the TV in, the screen flashes on and off and I hear a relay clicking repeatedly. This never changes no matter how long the TV is plugged in or what buttons are pressed.
The first test everyone recommends online is disconnecting the main TV board from the power supply board. This does not change the behavior at all. The speed of the click/flash changes a little bit but in general I believe the main TV board is not the issue.
What is interesting, and what I think makes this problem a little bit different than most, is that if I disconnect the two LED connectors from the power supply, the clicking stops -- if I then plug them back in one at a time, they both light up successfully and the TV then works and displays completely normally until I unplug it again. Once I unplug it again, the only way to get the backlight to work is to disconnect the LED connectors again and then reconnect them one at a time.
To me, the fact that the display works perfectly when I do this "gradual" startup suggests that there are no permanently failed components (shorted diodes, etc) and that the issue could be weak capacitors. It makes sense to my very inexperienced way of thinking that if there are one or more bad caps, then the power supply is incapable of making enough current to start up both LED strips at once, but starting them one at a time keeps the load low enough that the power supply is able to function.
Does that make any kind of sense? I know what bulged and leaky capacitors look like, and unless I am just overlooking something obvious, I don't see any on this board that appear to be bad, visually. I don't have a capacitance tester, only a multimeter. I think it does have a capacitance mode, possibly (Extech 430) but I believe the capacitors have to be removed from the circuit to check them, so I've not done that yet.
Can anyone point me to what I should test next, or if the theory that bad capacitors could cause these symptoms even makes sense? If I were going to replace the caps whether they need it or not just to rule them out, any guidance on which ones to do?
I have attached some pictures of the board (one view of the entire board, and then four quadrants in greater detail) and also a YouTube video showing the symptoms.
https://www.youtube.com/watch?v=5_lLSeetxvA
Thanks for any help you might be able to offer!
Mike
I'm hoping to get some help figuring out how to troubleshoot this power supply board. The television is a Samsung UN75J6300AFXZA, version no. UH03. The power supply board has two model numbers on it, L75S1 and BN44-00723C. As far as experience level, I'm familiar with recapping boards in terms of safely going through the soldering motions, choosing suitable replacement parts, and so forth, but as far as understanding the various functions of each part of these TV power supply boards, I am a rank beginner.
When I plug the TV in, the screen flashes on and off and I hear a relay clicking repeatedly. This never changes no matter how long the TV is plugged in or what buttons are pressed.
The first test everyone recommends online is disconnecting the main TV board from the power supply board. This does not change the behavior at all. The speed of the click/flash changes a little bit but in general I believe the main TV board is not the issue.
What is interesting, and what I think makes this problem a little bit different than most, is that if I disconnect the two LED connectors from the power supply, the clicking stops -- if I then plug them back in one at a time, they both light up successfully and the TV then works and displays completely normally until I unplug it again. Once I unplug it again, the only way to get the backlight to work is to disconnect the LED connectors again and then reconnect them one at a time.
To me, the fact that the display works perfectly when I do this "gradual" startup suggests that there are no permanently failed components (shorted diodes, etc) and that the issue could be weak capacitors. It makes sense to my very inexperienced way of thinking that if there are one or more bad caps, then the power supply is incapable of making enough current to start up both LED strips at once, but starting them one at a time keeps the load low enough that the power supply is able to function.
Does that make any kind of sense? I know what bulged and leaky capacitors look like, and unless I am just overlooking something obvious, I don't see any on this board that appear to be bad, visually. I don't have a capacitance tester, only a multimeter. I think it does have a capacitance mode, possibly (Extech 430) but I believe the capacitors have to be removed from the circuit to check them, so I've not done that yet.
Can anyone point me to what I should test next, or if the theory that bad capacitors could cause these symptoms even makes sense? If I were going to replace the caps whether they need it or not just to rule them out, any guidance on which ones to do?
I have attached some pictures of the board (one view of the entire board, and then four quadrants in greater detail) and also a YouTube video showing the symptoms.
https://www.youtube.com/watch?v=5_lLSeetxvA
Thanks for any help you might be able to offer!
Mike
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