Hello,
I got this TV (Westinghouse DWM40F1G1) that did not came on one day, blinked for a split second and turned off. I looked at it closer with flashlight and figured that the TV actually works, its just the backlight that does not.
There is one PCB board - all of the components are on it: TP.MS3393.P85
I took my oscilloscope and looked what is coming to the MOSFET that is switching current to LEDs - I could see that the PWM signal comes in but it cuts off almost instantly. I thought its the driver chip OB3350CP and so I replaced it.
After that the TV starter working again. For one week. And then exsctly the same problem came back.
I thought OK now I know what needs to be replaced and I replaced the driver chip AND the MOSFET thinking that maybe it gets some kind of "backlash" that kills the driver chip or whatever so I replaced both because I had ordered several of these parts for Aliexpress already. This time it did not help, the TV still blinks the backlight for a split second and thats it.
So I suspected the LEDs themselves, I got a LED strip tester (XY284-GHB) connected it straight to the wire going to LEDs and the backling came on. It takes about 50V and 40mA and stays on no problems. I can turn on the TV and operate it with the LED tester driving the backlight. I tried to lower the brightness setting to the minimum, then plugged in the backlight into the board but that still does not help.
At this point I dont know how to continue. I am guessing the LED driver chip (OB3350CP) mistakenly detects LED short or something and turns off. How do I troubleshoot from this point on?
Could not find a decent service manual for this board, all I could find is this link:
But the silkscreen designations do not match with schematics.
Any help welcome.
Thanks
I got this TV (Westinghouse DWM40F1G1) that did not came on one day, blinked for a split second and turned off. I looked at it closer with flashlight and figured that the TV actually works, its just the backlight that does not.
There is one PCB board - all of the components are on it: TP.MS3393.P85
I took my oscilloscope and looked what is coming to the MOSFET that is switching current to LEDs - I could see that the PWM signal comes in but it cuts off almost instantly. I thought its the driver chip OB3350CP and so I replaced it.
After that the TV starter working again. For one week. And then exsctly the same problem came back.
I thought OK now I know what needs to be replaced and I replaced the driver chip AND the MOSFET thinking that maybe it gets some kind of "backlash" that kills the driver chip or whatever so I replaced both because I had ordered several of these parts for Aliexpress already. This time it did not help, the TV still blinks the backlight for a split second and thats it.
So I suspected the LEDs themselves, I got a LED strip tester (XY284-GHB) connected it straight to the wire going to LEDs and the backling came on. It takes about 50V and 40mA and stays on no problems. I can turn on the TV and operate it with the LED tester driving the backlight. I tried to lower the brightness setting to the minimum, then plugged in the backlight into the board but that still does not help.
At this point I dont know how to continue. I am guessing the LED driver chip (OB3350CP) mistakenly detects LED short or something and turns off. How do I troubleshoot from this point on?
Could not find a decent service manual for this board, all I could find is this link:
But the silkscreen designations do not match with schematics.
Any help welcome.
Thanks
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