HP probook 4525s MB repair

[Honziq]

Hello,
my friend try change cracked LCD, bud he destroyed mainboard.
Mainboard is 09286-1 PATEK DIS MB.
All fuses on MB is OK, but when battery is connected coil L41 or L61 making beeping noise. When AC power is connected no noise is produced and R1251 became very hot. I try to remove U64 but still have this problem. Can enyone help me?
In attachment is images and schematics of this board. On page 39 is R1251 circuit. Thanks.

[khaahk]

Re: HP probook 4525s MB repair

measure resistance to gnd after R1251.
measure R1251 resistance, is it 100 ohm?

[Honziq]

Re: HP probook 4525s MB repair

measure resistance to gnd after R1251.
measure R1251 resistance, is it 100 ohm?

Yes R1251 is 100 ohm. Resistance to GND is about 850 ohm, reverse polarity resistance -> infinity.

[Honziq]

Re: HP probook 4525s MB repair

measure resistance to gnd after R1251.
measure R1251 resistance, is it 100 ohm?

When is on power, on resistor is 13,75V and voltage resistor to ground is 18,9V.

[rtstorm]

Re: HP probook 4525s MB repair

did you check the D60, D51, D53, D54 and C1195

[Honziq]

Re: HP probook 4525s MB repair

YES, diodes and capacitor is OK.
Diode D60 is connected directly to +19V Is it right?
But on schematic is D60 connected to VIN not to 19V.

[rtstorm]

Re: HP probook 4525s MB repair

DC jack is connected to VIN

[sorinac]

Re: HP probook 4525s MB repair

remove the R587 to cut the power to tps
and if the r1251 still heats then the zener diode d54 is defective.

[Honziq]

Re: HP probook 4525s MB repair

remove the R587 to cut the power to tps
and if the r1251 still heats then the zener diode d54 is defective.

By removing R587 heating stops.

[Honziq]

Re: HP probook 4525s MB repair

remove the R587 to cut the power to tps
and if the r1251 still heats then the zener diode d54 is defective.

What to do now? Please.

[Honziq]

Re: HP probook 4525s MB repair

DC jack is connected to VIN

Thanks for help.

[khaahk]

Re: HP probook 4525s MB repair

If your friend tried to change a lcd with battery connected, then the most common thing to happen, is that kbc gets killed. If you remove the lcd panel does the R1251 still heat up?
Voltages on coil L47 and L48? Does U64 heat up?
How much current does the circuit draw when connected to AC?

[Honziq]

Re: HP probook 4525s MB repair

If your friend tried to change a lcd with battery connected, then the most common thing to happen, is that kbc gets killed. If you remove the lcd panel does the R1251 still heat up?
Voltages on coil L47 and L48? Does U64 heat up?
How much current does the circuit draw when connected to AC?

Yes I measuring it without LCD and R1251 is Heating.
When I remove U64 its still heating.
On L47 and L48 is 0V.
On PIN 1 and 3 of U64 Is 1,68V
On pin 8 is 1,89V
On pin 16 IS 4,59V
On pin 17 is 2,12V.
U64 Heats up just a little.
My friend replaced LCD with LCD from HP 4510s, but he changed it with LVDS cable. Cable from HP 4510s is not the same I hink this is the problem.
In attachment you can see the difference between cables. LVDS from HP Probook 4510s have all pins connected, but LVDS from 4525s NOT, some pins is empty. Circuit draws 130mA when I measuring on R587.
Maybe its normal resistor heating so much.

[khaahk]

Re: HP probook 4525s MB repair

Removing U64 without removing its connected power FETs is dangerous. The gates are in the air and might get charged and start driving - and you get adapter voltage on 3V rail and goodbye mainboard.
I think you've got overloaded LDO output at 3V (pin 8 should be 3V). If you own a lab PSU, then try to find short in that rail. The schematics (if correct) show that the pinout is identical to 4515, the cable might be different depending on the panel size (two lvds channels for 17 inch panel).
Still hard to explain why R1251 heats up when U64 is missing...

[Honziq]

Re: HP probook 4525s MB repair

Removing U64 without removing its connected power FETs is dangerous. The gates are in the air and might get charged and start driving - and you get adapter voltage on 3V rail and goodbye mainboard.
I think you've got overloaded LDO output at 3V (pin 8 should be 3V). If you own a lab PSU, then try to find short in that rail. The schematics (if correct) show that the pinout is identical to 4515, the cable might be different depending on the panel size (two lvds channels for 17 inch panel).
Still hard to explain why R1251 heats up when U64 is missing...

I soldered back the U64 and all voltages are the same as before removing it.
But I still have no Idea how he can kill board by LCD. He says: I just changed LCD, then power on Laptop. Led blinks and then shutoff. After this i cant power on the laptop with or without battery, with old or new LCD.
I havent lab PSU. Its time to say Bye Bye Board.

[Honziq]

Re: HP probook 4525s MB repair

Now I find shorted mosfet U35.

[khaahk]

Re: HP probook 4525s MB repair

Short is how many ohms?
Is it shorted off-board also?

[Honziq]

Re: HP probook 4525s MB repair

Short is how many ohms?
Is it shorted off-board also?

Shorted is 0Ohm, off board it is still 0Ohm, but U58 is now shorted too.