Ask HP ProBook 450-G2 No Backlight LA-B181P

[sikocan]

BOARD: LA-B181P
LAPTOP: HP probook 450 g2
ISSUE: NO BACK LIGHT.
HISTORY: Unknown
CONDITION: Works normal without backlight, has picture. Works external screen.
Repair Steps: 3 different LCDs tried so far. No damage/burnt or liquid spills.
Attached is the LVDS connector readings with LCD, without LCD and their Voltages.
Also attached is the PDF schematics.

[mon2]

Re: Ask HP ProBook 450-G2 No Backlight LA-B181P

Another case the same on this forum.

Measure and post the voltage readings of each pin of UT6 AND gate.

[sikocan]

Re: Ask HP ProBook 450-G2 No Backlight LA-B181P

The readings are:

1. 0
2. 3.39
3. Ground 0
4. 3.39
5. 3.39

I could be wrong on numbering, there is no IC in this location, just pads. I've attached the image.

[sikocan]

Re: Ask HP ProBook 450-G2 No Backlight LA-B181P

I have tried a new BIOS file same result. The cable in continuity looks good to all pins with a cable.

[mon2]

Re: Ask HP ProBook 450-G2 No Backlight LA-B181P

Ok. Appears to be not stuffed so is bypassed.

Confirm the voltages to ground on pins 8 & 9 on the LVDS connector.

[sikocan]

Re: Ask HP ProBook 450-G2 No Backlight LA-B181P

Pin 8 3.11
Pin 9 3.39

[sikocan]

Re: Ask HP ProBook 450-G2 No Backlight LA-B181P

On ERS Discord, a friend mentioned INVTPWM is for brightness. Before BIOS reset it was 3.39V and after reset it was 3.11. Hence the difference in my original readings and current readings. Is this correct?

[piernov]

Re: Ask HP ProBook 450-G2 No Backlight LA-B181P

Cable is suspect if it's not been replaced. Voltages should be checked on LCD side to confirm.

[sikocan]

Re: Ask HP ProBook 450-G2 No Backlight LA-B181P

Just an update to LCD issues on HP ProBook - No solution yet. I have attached PDF file which shows LCD side Pin voltages when it's turned on. Let me know what you think. Green background of a cell means there is a match on LCD. Red means V on screen but no corresponding match on LVDS.

[sikocan]

Re: Ask HP ProBook 450-G2 No Backlight LA-B181P

Pin No 9 is fault. resoldered fixed.