HP 14XL352, 14XL250, 14XL355, 14XL246 Backlight brightness cannot be adjusted with Fn+F7 or Fn+F8

Presario 1400 Series

Models: XL240, XL241, XL242, XL244, XL245, XL246, XL247, XL250, XL340, XL341, XL342, XL343, XL344, XL345, XL346, XL350, XL352, XL355, and XL356

Solving Display Problems

Problem

The light tubes on the edge of the display panel do not light up, and the Power-On Self-Test (POST) completes when the unit is powered up.**

The light tubes on the edge of the display panel do not light up, and the Power-On Self- Test (POST) does not complete when the unit is powered up.**

Backlight (brightness) cannot be adjusted with Fn+F7 or Fn+F8.

Probable Cause

Improper backlight or display cable connections

Defective inverter board

Defective display cable

Defective display panel

Defective system board

Defective system board

Improper display cable connections

Defective inverter board

Defective display cable

Defective system board

Solution

Replace the display assembly.

Replace the display assembly.

Replace the display assembly.

Replace the display assembly.

Replace the system board.

Replace the system board.

1.Reseat the display cable to the system board.

2.Replace the display assembly.

Replace the display assembly.

Replace the display assembly.

Replace the system board.

**This problem indicates that the backlight or its power circuitry has failed. Since you cannot observe the POST results on the display panel when the backlight is not functioning, connect the unit to an external monitor before powering it up. If an external monitor is not available, confirm that POST completes by opening and closing the display, listening for the single or double beep and watching for the icons to turn on at the front of the Notebook.

Continued

PRESARIO NOTEBOOK MAINTENANCE AND SERVICE GUIDE 1400 SERIES TROUBLESHOOTING 25