This set has the known reputation of failed led backlights. The set does not turn on, but when plugged in, the power led stays lit for about 5 seconds followed by two short blinks and then it repeats itself. While shinning a flashlight on the screen, you can make out the Sharp logo, then it goes out and repeats the cycle. I measured some voltages across the led backlight connector. What has me puzzled is that when I place the negative lead of my vom on the led backlight pin connector (in which the black wire going to the leds was), I measure as high as -228volts, and then it falls to -95 volts and repeats the cycle. I was expecting the voltage to be the opposite polarity (+228 volts falling down to +95 volts). Perhaps, it is because the color of the wire being black is usually associated with negative or ground. Should I be concerned about the polarity or just assume that the wire color (black) has nothing to do with the negative terminal. And the red colored wire really goes to the cathode of the led string. I also measured the voltages on connector XP805 (8pin connector) going from power supply board to main board. I measure 2.91 volts on the pin (SB) standby and 12 volts on the other 2 pins designated 12 volts on the legend.
I believe that I have a open in Led backlight circuit which is causing the set to shut down. Is there anything that I should do to verify my prognosis before taking apart the screen? BTW, I do not have an Led backlight tester, but once I get access the the leds strips, I can test the strip or leds individually. Thank you.
I believe that I have a open in Led backlight circuit which is causing the set to shut down. Is there anything that I should do to verify my prognosis before taking apart the screen? BTW, I do not have an Led backlight tester, but once I get access the the leds strips, I can test the strip or leds individually. Thank you.
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