hp elitebook 840 g3 power problem

[jacospama]

Am working on hp elitebook 840 g3 . the problem is , it can only turn on when i put in charge battery but not on charger. if i plug in the charger all the necessary voltages come , but still cant switch on from charger. is there way through which i can solve this problem?

[mon2]

Re: hp elitebook 840 g3 power problem

Sounds like a common DCin mosfet fault - see the above sticky by @Piernov on how charging functions on laptops.

Post the logic board markings so we can hunt down the logic board schematic (if they are available).

Using a multimeter; hot air tools and some patience, you should be able to repair this unit.

First need to review which charger IC is onboard this design. Respectively, you should have 2 x DCin mosfets (likely will be N-channel style).

Often the 2nd DCin mosfet gets damaged and needs to be replaced.

[Stevedb]

Re: hp elitebook 840 g3 power problem

Do you use original adapter of correct wattage.

[jacospama]

Re: hp elitebook 840 g3 power problem

Do you use original adapter of correct wattage.

am using original charger

[jacospama]

Re: hp elitebook 840 g3 power problem

Sounds like a common DCin mosfet fault - see the above sticky by @Piernov on how charging functions on laptops.

Post the logic board markings so we can hunt down the logic board schematic (if they are available).

Using a multimeter; hot air tools and some patience, you should be able to repair this unit.

First need to review which charger IC is onboard this design. Respectively, you should have 2 x DCin mosfets (likely will be N-channel style).

Often the 2nd DCin mosfet gets damaged and needs to be replaced.

this is the board

[mon2]

Re: hp elitebook 840 g3 power problem

See attached. Near the battery connector should be the charger IC. We need to locate this charger IC to debug this case.

Is the IC with a 'BQ' marking ? If not, continue to locate similar looking square ICs till you find the 'BQ' charger IC.

[jacospama]

Re: hp elitebook 840 g3 power problem

See attached. Near the battery connector should be the charger IC. We need to locate this charger IC to debug this case.

Is the IC with a 'BQ' marking ? If not, continue to locate similar looking square ICs till you find the 'BQ' charger IC.

ok thank you. but please how can i locate BQ charger ic?

[mon2]

Re: hp elitebook 840 g3 power problem

Review each square (black in color) shaped IC and review the topside markings.

Guessing that you will have one with 'BQ' in the markings = Texas Instruments / BenchmarQ brand. We need to know the full part number on this IC.

Start the hunt from the DCin adapter connector and review to the battery connector. Has to be present somewhere.

[jacospama]

Re: hp elitebook 840 g3 power problem

Review each square (black in color) shaped IC and review the topside markings.

Guessing that you will have one with 'BQ' in the markings = Texas Instruments / BenchmarQ brand. We need to know the full part number on this IC.

Start the hunt from the DCin adapter connector and review to the battery connector. Has to be present somewhere.

i have seen the ic

[jacospama]

Re: hp elitebook 840 g3 power problem

Review each square (black in color) shaped IC and review the topside markings.

Guessing that you will have one with 'BQ' in the markings = Texas Instruments / BenchmarQ brand. We need to know the full part number on this IC.

Start the hunt from the DCin adapter connector and review to the battery connector. Has to be present somewhere.

please should i replace ic ?

[mon2]

Re: hp elitebook 840 g3 power problem

What are the full markings of this charger IC ? So far, unable to locate the schematic for this logic board ->> Use 840 G1 (similar) schematics.

However, with the charger IC details, we can get a very close idea of how this charger circuit works to debug the fault.

Update: HP 840 G1 also has a U6000 for the charger IC so use it for reference.

Download the schematic from here:

https://www.badcaps.net/forum/showth...ghlight=840+g1

Then search for 'U6000'.

Measure the voltage to ground for the following pins on U6000:

a) REGN

b) ACDRV

[jacospama]

Re: hp elitebook 840 g3 power problem

What are the full markings of this charger IC ? So far, unable to locate the schematic for this logic board ->> Use 840 G1 (similar) schematics.

However, with the charger IC details, we can get a very close idea of how this charger circuit works to debug the fault.

Update: HP 840 G1 also has a U6000 for the charger IC so use it for reference.

Download the schematic from here:

https://www.badcaps.net/forum/showth...ghlight=840+g1

Then search for 'U6000'.

Measure the voltage to ground for the following pins on U6000:

a) REGN

b) ACDRV

Ok am gonna do that thank you

[mon2]

Re: hp elitebook 840 g3 power problem

I think you may find that the 2nd mosfet = Q6011 will be defective.

You can remove it and confirm that ACDRV should be ~25 volts to ENABLE the 2 x DCin mosfets. If it is not, then we need to review the conditions needed for this charger IC to spit out this boosted voltage.

That is, the ACDRV voltage should be (if working properly) = DCin adapter + REGN voltage (~6 volts) = ~25 volts to enable the mosfets.

Often, as per article above by @Piernov, the 2nd mosfet gets damaged. DO NOT bypass the mosfet but if available, replace it with a suitable N-channel device. The device can be replaced by many others.

Test and post your updates for future readers.

[classicandy]

Re: hp elitebook 840 g3 power problem

What are the full markings of this charger IC ? So far, unable to locate the schematic for this logic board ->> Use 840 G1 (similar) schematics.

However, with the charger IC details, we can get a very close idea of how this charger circuit works to debug the fault.

Update: HP 840 G1 also has a U6000 for the charger IC so use it for reference.

Download the schematic from here:

https://www.badcaps.net/forum/showth...ghlight=840+g1

Then search for 'U6000'.

Measure the voltage to ground for the following pins on U6000:

a) REGN

b) ACDRV

This board uses BQ24780S...... Same as HP Elitebook 1040 g3, 1030 g2 and most 6th and 7th Generation HP Elitebooks and Probooks Series

[spyro99]

Re: hp elitebook 840 g3 power problem

I think you may find that the 2nd mosfet = Q6011 will be defective.

You can remove it and confirm that ACDRV should be ~25 volts to ENABLE the 2 x DCin mosfets. If it is not, then we need to review the conditions needed for this charger IC to spit out this boosted voltage.

That is, the ACDRV voltage should be (if working properly) = DCin adapter + REGN voltage (~6 volts) = ~25 volts to enable the mosfets.

Often, as per article above by @Piernov, the 2nd mosfet gets damaged. DO NOT bypass the mosfet but if available, replace it with a suitable N-channel device. The device can be replaced by many others.

Test and post your updates for future readers.

you saved my sanity

Replaced bq 3 times tested mosfets they looked ok no shorts tested all the caps, checked for voltages in bq and had no voltage in ACDRV only 6v in REGN , in "desperation" replaced q6011 and everything is working now