HP EliteBook 840 G2 power problem

[Techtiger]

Re: HP EliteBook 840 G2 power problem

There was an official update, so I tested it. The charger was recognized by the bios update program, it would not work otherwise. Now nothing happens. I will measure resistance as soon as I get home from work.

The charger is recognized by the bios but not windows ?

[bollin]

Re: HP EliteBook 840 G2 power problem

The charger is recognized by the bios but not windows ?

It was, yes. PVBATis 11.4 volts with battery only, 19.4 volts on ac but dropping to 17 volts at the same rate the ticking is heard. PVPACK is 11.4 volts battery only and 1.5 volts on ac only and rising to 2 volts at the same rate the ticking is heard. Q6000 and q6001 are confirmed good, and tgat makes me believe it is a faulty u6000

[bollin]

Re: HP EliteBook 840 G2 power problem

HIDRV is 11.4 volts with both battery only and battery + ac. On ac only it is at 1.5 volt rising to 2 volts at the same rate as the ticking.

[bollin]

Re: HP EliteBook 840 G2 power problem

Here are the voltages on u6000

U6000 with only AC Adapter:

Pin1: 19.4- 17v
2: 19.4- 17v
3: 19.4-17v
4: 25.3-22.4v
5: 0v - 1.35v
6: 2.5v
7: 0v
8: 3.2-3.3v
9: 3.2v
10: 3.2v
11: 0v
12: 2v-1.3v
13: 2v-1.35v
14: 0v
15: 0v
16: 5.92v-5.85v
17: 5.76v-5.7v
18: 2v-1.35v
19: 2v-1.35v
20: 19.4v-17v

Battery connector:

1: 1.6v-1.1v
2: -"-
3: 3.3v
4: 3.3v
5: 0v
6: 3.27v-3.25v
7: 0v
8: 0v

U6000 with AC Adapter and battery connected:

1: 11.69v
2: 11.69v
3: 0.11v
4: 0.03v
5: 3.28v
6: 2.63v
7: 0v
8: 3.29v
9: 3.29v
10: 3.27v
11: 0.01v
12: 11.69v
13: 11.69v
14: 0v
15: 0v
16: 5.92v
17: 11.42v
18: 11.68v
19: 11.68v
20: 11.68v

Battery connector:

1: 11.68v
2: 11.68v
3: 3.3v
4: 3.3v
5: 0v
6: 0v
7: 0v
8: 0v

I would like to add that in the first measures the voltages were most of the time like the first reading but once every se ond jumped to The second reading, hence the varying readings. There were also a a faint ticking sound about once every second, and that went away with the battery present.

Shouldn't acdrv be cmsrc + 6 volts for q6011 to open? But cmsrc is only 0.11 volts with battery and charger connected, but 19.5 volts without battery. I will recheck values tonigjt.

[bollin]

Re: HP EliteBook 840 G2 power problem

New turn: after a reinstall of windows due to a unrelated problem, some HP software is now telling me that the smart adapter is not working and that I should replace it. It does however work on my wifes 840 g2, and I get the same message when using her charger on my computer. Back to square 1...

[bollin]

Re: HP EliteBook 840 G2 power problem

New info: Limit_signal is at 0.16v, should be at 2.7 volts... that's why it doesn't recognize any chargers...

[bollin]

Re: HP EliteBook 840 G2 power problem

SOLVED! The problem was the DC Jack, or rather a poor connection to the center pin. After I read about someone who had the same problem and solved it by crimping the DC jack I measured and found that it did not connect that well. I took a pair of pliers and crimped the base of the DC jack, after that it worked like new!

[Techtiger]

Re: HP EliteBook 840 G2 power problem

SOLVED! The problem was the DC Jack, or rather a poor connection to the center pin. After I read about someone who had the same problem and solved it by crimping the DC jack I measured and found that it did not connect that well. I took a pair of pliers and crimped the base of the DC jack, after that it worked like new!

Good job

[Stevedb]

Re: HP EliteBook 840 G2 power problem

@bollin

What do you mean with crimping base of the dc jack?

Regards

Steve

[bollin]

Re: HP EliteBook 840 G2 power problem

I mean that I used a pair of pliers to make the dc jack connector on the motherboard tighter, and that way improve the connection.

[bollin]

Re: HP EliteBook 840 G2 power problem

Like this, and in this end:

[Stevedb]

Re: HP EliteBook 840 G2 power problem

Ok thank you very much

[ch3sco]

Re: HP EliteBook 840 G2 power problem

Good job

Do you remember the voltages on pin 1, 2 and 3 of the power jack?

I'm having some issues, and i think is also the powerjack.

but I read around 19V on pins 1 and 3.

and have a reading of 1.2V on pin 2, but this one seems to have bad contact.

I hope you can answer,

thanks

[muhammed201]

Re: HP EliteBook 840 G2 power problem

SOLVED! The problem was the DC Jack, or rather a poor connection to the center pin. After I read about someone who had the same problem and solved it by crimping the DC jack I measured and found that it did not connect that well. I took a pair of pliers and crimped the base of the DC jack, after that it worked like new!

Thanks Thanks Thanks. l have got also same problem and solved thanks to you. All voltage was okay every thing was okay but it wasnt work. When l changed socket its okay now.

[Tofandel]

Re: HP EliteBook 840 G2 power problem

Sorry for hijacking but I have a problem in the same circuitry, for me the laptop turns on with the adapter and shows battery charging etc but when disconnected it shuts off and doesn't turn on just on battery. The battery is good with 12v voltage but probing PBPACK is at 4v everywhere after Q6051 which I'm guessing is the issue

For some context there was a shorted cap (C6010) which I removed (didn't replace yet as I don't have 10uf 25v on hand) but which shouldn't be a problem if it's not present

This short likely created another failure somewhere since now the battery is not supplying power which is what I'm trying to track down and I could use some pointers

I'm really not familiar with switching supply

[mon2]

Re: HP EliteBook 840 G2 power problem

Remove all power. Meter in resistance mode.

Measure the resistance across the mosfet:

Source & drain
Source & gate
Gate & drain

Post each measurement and the meter scale used for the measurements.

Check q6051 and q6050 for starters. If the readings are low, the mosfet is shorted and must be replaced.

[Tofandel]

Re: HP EliteBook 840 G2 power problem

Thanks

It's indeed a shorted mosfet (Q6051) after testing the resistance between gate & drain there was only a few ohms (not dead short, but shorted enough that the source was only 4v instead of 12v)

It was very hard to unsolder, it's entirely soldered underneath and there is a very small 10k resistor just next to it

[mon2]

Re: HP EliteBook 840 G2 power problem

My suggestion is that either you source the proper tools to remove this mosfet or consider to take to a local cellphone or computer shop that can do the same. You need a good hot air tool with flux. Underside pre-heater will also help for heating up multilayer pcbs. Ask around if someone local to you services at the component level.

Cellphone repair shops will have the tools and experience to do this without losing the surrounding parts. You will need to find the replacement mosfet. This can be the same one or an equivalent. Same one can be found on AliExpress. If required, can search for a replacement.