Nitro 5 Motherboard: LA-F991P LCD Backlight Problem

[Ado02]

Hi,

I am currently working on a Nitro 5 laptop that came in with an issue involving the hinge and the LCD cable. The LCD cable has been replaced, and so has the screen. However, I am encountering a problem with getting the backlight to work.

While I am not an expert in this area, I suspect that PCH_BLK_PWM and BKOFF may be related to the backlight circuit. However, both of these components lead to integrated circuits (ICs), which makes it challenging for me to perform any checks.

Does anyone have any suggestions on where I should begin troubleshooting?

Schematics and Boardview are attached.

MOD Edit, Link to schematic https://www.badcaps.net/forum/showthread.php?t=79357

Reminder: rules and organization of this section https://www.badcaps.net/forum/showthread.php?t=117483
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[Ado02]

Re: Nitro 5 Motherboard: LA-F991P LCD Backlight Problem

Can anyone help with this?

[reformatt]

Re: Nitro 5 Motherboard: LA-F991P LCD Backlight Problem

First up, did you disconnect the battery during cable replacement? This can in some cases cause board damage if not.

Need to establish first whether you do indeed have an image on the screen minus the backlight. Backlight won't be enabled unless the display is communicating via the EDP datalines to the CPU. Check for presence of +INVPWR_B+ (19V), +LCDVDD (3V) first. The latter will initially come on during boot, and switch off if no communication from the LCD is received.

BKOFF# should be 3V for backlight enable if the LCD is detected. PCH_BLK_PWM should be a square wave, duty cycle is varied to adjust screen brightness.