Technical Support HP Elitebook 840 G3

[irepairs]

No power, I noticed Q60011 N-Channel Mosfet was burnt out , I replaced it. Now I have 5V, 3.3V, 1.8V voltage rails. The laptop still doesn't turn on. The battery inductor is giving 0V when I do the diode test for Hi and Low Mosfets. I also replaced the dual N-Channel Mosftet (Hi and Low) beside the battery (Q66010). Also one voltage rail (I think 1.05V, no schematics available) is giving 180mV. The laptop is still not turning on, any ideas? Please see attached images.

 

[Ahmad Safari]

HI..
1.05V voltage enters the chipset, and if you have a problem in the consumer, the chip is damaged, and if the manufacturer has a problem, the PWM circuit should be checked.

 

[irepairs]

Thank you , I will check. What about the battery inductor is it normal to have 0V Diode test and 20 Ohms.

 

[irepairs]

I changed the Charging IC because I saw that Pin 26 related to HIDRV is not stable. Now the laptop turns on but the battery is not charging. It says charging when I logon to Windows but it doesn't charge and the inductor closed to battery measures 0V.

 

[Ahmad Safari]

The ohm of the battery inductor must be high, usually above 30 kilo ohms.
If you have an oscilloscope, check the signal on the gate pin of the MOSFETs. If the signal is not correct, check the pwm circuit of the battery charge, including the MOSFETs and ICs.
Also Test with a reliable battery.

 

[irepairs]

Hello, I checked PWM and MOSFETs all good however I noticed BATPRES is shorted to GND. Also when I connect the battery without AC Adapter the voltage is 0V. Battery disconnected is 11V. Pin 15 of the charger IC BATPRES is shorted. Where does this signal come from?

 

[irepairs]

Attached is the charger IC datasheet

 

[Ahmad Safari]

Hello, I checked PWM and MOSFETs all good however I noticed BATPRES is shorted to GND. Also when I connect the battery without AC Adapter the voltage is 0V. Battery disconnected is 11V. Pin 15 of the charger IC BATPRES is shorted. Where does this signal come from?

When the battery is placed on the device, pin 15 is connected to the ground from inside the battery so that the battery is recognized by IC and this pin is normal.

 

[Ahmad Safari]

HP laptop is very sensitive to the adapter.
The path of detect adapter that enters EC IC is very important.
The absence of this signal and its non-recognition will cause the battery not to charge.

 

[irepairs]

But according to schematics Pin 15 should be active high when no battery exists and active low when battery is plugged. In both cases pin 15 is measuring 0V.

 

[Ahmad Safari]

Replace the charging IC again and re-solder the pins under the loop.

 

[irepairs]

I have done that and I made sure all pins are resoldered properly. Please see attached the values I am getting on all pins of the charger IC. The values below is taken when the AC Adapter is plugged to the board with no battery.

 

[irepairs]

Hello, I want to let you know that this fixed the issue and the battery is charging , I also replaced a 10 ohm resistor on pin 28 that was open.

 

[Ahmad Safari]

Pin 11 should be 3.2 volts, which transfers information between the battery and the charging IC and EC.
If the battery and IC are replaced, the EC may be damaged.


If your motherboard does not have a schematic, you can get help from other boards that have similar ICs and their schematics are available.

 

[irepairs]

I see, I didn't test the pull up resistors but it's working now and the battery is charging normal.