HP Probook 4510S BACKLIGHT PROBLEM

[ramzi2019]

Hello everyone,
I'm a beginner so don't blame me.
I'm getting data in the screen with no backlight. The screen is OK and I've tested with a second data cable.
So i'm getting this voltages in the motherboard connector. I need your help!

[piernov]

Re: HP Probook 4510S BACKLIGHT PROBLEM

Measure voltage on all pins of U1.

[ramzi2019]

Re: HP Probook 4510S BACKLIGHT PROBLEM

Thanks for the help

[piernov]

Re: HP Probook 4510S BACKLIGHT PROBLEM

Correct schematics for your board attached.
Measure voltage on all pins of U5001.

[MOD EDIT] Link to Schematic -> https://www.badcaps.net/forum/troubl...411s-schematic

[ramzi2019]

Re: HP Probook 4510S BACKLIGHT PROBLEM

Sorry for the mistake

[piernov]

Re: HP Probook 4510S BACKLIGHT PROBLEM

Recheck voltage on LCD connector CN4021 because if you have 3V on pin 4 of U5001, you should have 3V on pin 32 of LCD connector CN4021.

[ramzi2019]

Re: HP Probook 4510S BACKLIGHT PROBLEM

Sorry for being late.
But i have found that pin 4 of U5001 is going to pin 36 of CN4021.

[piernov]

Re: HP Probook 4510S BACKLIGHT PROBLEM

Hum… on the schematics, pin 36 is connected to +VBATR (also connected to pin 38 and 40). It's the main power rail for backlight.
Anyway for backlight you need the enable signal (output on pin 4 of U5001), PWM signal (called INV_PWM_3 on pin 40) and backlight power rail (+VBATR on pin 36/38/40).

[ramzi2019]

Re: HP Probook 4510S BACKLIGHT PROBLEM

For more clarification, The exact name in the motherboard is foxconn ml1-h94v-0 E253117.
And I want to correct you: The backlight power rail (+VBATR) is on pin (34/36/38) and
according to this fact, i must have continuity between them and same volt reading. But this is not the case (Photo on post 1 with taken measure).
The LCD connector CN4021 seems to be strongly soldered to the motherboard.

[piernov]

Re: HP Probook 4510S BACKLIGHT PROBLEM

"foxconn ml1-h94v-0 E253117" is just generic marking of PCB, not the motherboard model number.

CN4021 is numbered like this:
2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39

Pin 1 bottom left with the small notch.

[ramzi2019]

Re: HP Probook 4510S BACKLIGHT PROBLEM

Sorry for the mistake and thanks for your great help.
I've to recheck all.

[ramzi2019]

Re: HP Probook 4510S BACKLIGHT PROBLEM

This is the new result.
I'm suspecting that the 1.42v of pin 40 may be the problem?

[piernov]

Re: HP Probook 4510S BACKLIGHT PROBLEM

Pin 40 is a PWM signal, voltage doesn't really tell what it looks like but it means the signal is present. For testing you can short it to 3.3V, it will force full brightness.
Other voltages are ok. If you don't get backlight even when shorting PWM to 3.3V, it's an issue with the cable or the panel.

[ramzi2019]

Re: HP Probook 4510S BACKLIGHT PROBLEM

I have found that pin 40 is shorted to ground (i used continuity test). Is it normal?

[ktmmotocross]

Re: HP Probook 4510S BACKLIGHT PROBLEM

I have found that pin 40 is shorted to ground (i used continuity test). Is it normal?

how u could have 1,4V on pin shorted to ground?

u have boardview and schematic and u cannot do one good measurement?

how u could think u can do a repair?

[ramzi2019]

Re: HP Probook 4510S BACKLIGHT PROBLEM

Thank you for your advice.
I give up.

[SMDFlea]

Re: HP Probook 4510S BACKLIGHT PROBLEM

Can you find C1276 on the board

[ramzi2019]

Re: HP Probook 4510S BACKLIGHT PROBLEM

Thanks for all the good people in this board.
finally, i made it.
In order to avoid any trouble, i isolated the pin 40 from the board (Is no longer soldered) and bridged 3v to it.
So the backlight is working again.
This is old and strange but the result is good.
I attached a compressed file with some photos as a proof.