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hello I repair an ASUS F554L Laptop with broken display. I bought a new display panel but this shows no backlight. The LCD part works, putting a light source behind shows the LCD works correct. I have for first a simple question: Does anybody know if the backlight inverter is on the panel or on the motherboard. If the inverter is on the motherboard, where does it sit ? If not, could this be a display panel cable problem ? Other information: After startup of windows 10, the external display ports (VGA / HDMI) work fine. Many thanks for an answer. /medard
The LED boost converter should be integrated to the LCD panel. The voltage for the backlight is available on pin 1/2/3 of the LCD connector. You can check that you get 19V there (with the AC adapter and the display plugged in) to make sure the motherboard is working. There’s also an enable signal on pin 5 which should be 3.3V, and a PWM brightness control signal on pin 6 which should be close to 3.3V at full brightness. Also make sure the LCD panel you got indeed has an integrated LED controller. Then you can suspect the LCD cable or the panel itself. Clean the cable at both ends with some contact cleaner and make sure it’s seated properly. To eliminate the LCD cable being the issue, you can check at the panel side if you also get the required voltages.
