HP LAptop : CTL51/53 LA-E831P Issue: Laptop turn on OK but No Display ... External Display HDMI works fine... i changed the whole LCD assembly with the ribbon cable and still same issue, its not a Backlight issue cause i raise led backlight to full 3.3v with the PWM and still nothing displayed on screen ... LCDVDD is High, 19Volt PResent and another 3.3v is present also ... LID_SW# is high ... its a discrete Motherboard ... and Schematic Unavailable ... Could it be a BIOS issue ??

There is an image on an external monitor. does it enter BIOS?
Was the native display from this laptop checked on another laptop?
And by the way, write a revision of the LA-E831P board, as there are several revisions!
Народ человек просит схему на эту плату, скиньте кому не жалко!!!

Ya and ican enter Bios ... and can enter Windows also


ya and it worked fine


revision is 2.0

Send a photo of the board. The BIOS is normal. Loop matrix ring on a cliff. Do you have matrix power?
I have not schematic for this motherboard

Hello battery13v!

1. Disconnect battery and power adapter.
2. Find pinout of display edp connector.
3. Using beep mode of yours digital multimeter find backlight on signal (BLON/DISPOFF#/etc), PWM brightness control (BLPWM), 3.3V, 19Vat JEDP connector on motherboard. Take a photo of JEDP and sign on the photo this signals.
4. Then try to find path of BLON from JEDP to KB9022Q.
5. After that connect power adapter, power on and try to carefully measure BLON voltage near JEDP or KB9022Q.

JEDP pinout LA-E831P:
4,5 MLO (Main-Lane)
7,8 AUX (Auxiliary Channel)
9,10 VCCS (Power Supply +3.3V)
11 HPD (Hot Plug Detect)
15 LED_EN (BL_ENABLE Signal of LED Converter)
16 LED_PWM (PWM Dimming Control Signal)
19,20 LCD_VCCS (BL Power)