Troubles with HP pro x2 612 g2

[mon2]

Re: Troubles with HP pro x2 612 g2

If confident on Mohms, ignore it - that is ok. Concerned about the lower resistance readings.

Make a note of the readings and post them here.

Next, with extreme care, remove the battery and attach only the external power adapter to power this logic board.

Then with meter in DC volts scale of 20V or higher, red meter probe on pin # 4 = gate pin of the mosfets you have found for the DCin.

Black meter probe to ground.

What is the voltage you are reading for the GATE pin # 4 ?

Also review the voltage on the SOURCE (1-2-3) and DRAIN (5-6-7-8) of each of these 2 x DCin mosfets.

With the absence of the battery, the external power adapter should allow for the voltage to travel through onto the logic board but to do this, the ACDRV pin should enable the onboard mosfets. Confirm the voltage readings.

[johnjohnjohnjohn]

Re: Troubles with HP pro x2 612 g2

I borrowed my kids slate

[johnjohnjohnjohn]

Re: Troubles with HP pro x2 612 g2

17.8v on the two gates (pin 4)

[johnjohnjohnjohn]

Re: Troubles with HP pro x2 612 g2

11.9 V on both sources and drains

[mon2]

Re: Troubles with HP pro x2 612 g2

Ok. The 420k may be too low and could be indicating this mosfet to be leaking.

What voltage do you read on the source & drain of each of these mosfets ? Red meter probe to SOURCE; black to ground.

You have a TI (BenchMarq) charger IC which use N-channel mosfets. With N-channel mosfets, the gate voltage is required to be higher than the voltage it is passing to enable the mosfet to be full on (like a full on water tap).

Curious to know the voltage being fed into these mosfets.

[johnjohnjohnjohn]

Re: Troubles with HP pro x2 612 g2

so, the values are the same for the two mosfets : the gate receive 17.8V
the source and drains are at 11.89V

[johnjohnjohnjohn]

Re: Troubles with HP pro x2 612 g2

all these measures are done on DC, without battery

[johnjohnjohnjohn]

Re: Troubles with HP pro x2 612 g2

so the strange part was that : if I put the charger, without the battery, the pc power on. If I put the battery alone, without the charger, the pc power on.
If I plug the charger, when the pc is off but with battery plugged in, the port doesn t light up, nothing turns on, even when pressing power.
If I "hot plug" the battery while the pc is on, on charger, then the battery is recognized after a few seconds, and charges.
If I then unplug the charger, the battery doesn t take relay instantly, the pc turn off. And back to step one. You see ?

[mon2]

Re: Troubles with HP pro x2 612 g2

Ok. These 2 x DCin mosfets look to be ok since the drains are ~12 volts (the power delivery contract selected by this logic board and sent out from the external adapter).

The gate has to be ~6 volts higher than the voltage to pass through = ~18 volts which is what you are measuring. This appears to be ok.

Next, locate the other mosfets on this logic board. Specifically, look for the BATTERY MOSFET that is acting like a switch between the logic board main power rail and the battery.

What the adapter is applied, this mosfet should remain OFF. When the adapter is removed, this mosfet is to be ON.

This mosfet is driven by the BATDRV pin of the charger IC. It should also be 8 pins like the others.

With NO power to the board, meter in resistance mode. Locate the battery mosfet and check again the resistance between the GATE pin # 4 and this charger IC BATDRV pin. This is to confirm we have found the proper mosfet. Once that mosfet is found, perform the same resistance checks across the mosfet pins like you did with the DCin mosfets.

Post all readings.

[johnjohnjohnjohn]

Re: Troubles with HP pro x2 612 g2

the mosfet 7414, just beside the two DC ones
It shows measures in the MOhms for all combinations
I just tried quickly to power on with battery only, and the BATDRV pin is 14.3V and this mosfet gets 8.3 V trough it

[johnjohnjohnjohn]

Re: Troubles with HP pro x2 612 g2

the 6V you said that was needed, so.

[mon2]

Re: Troubles with HP pro x2 612 g2

Good readings.

Next, remove all power -> check the resistance across this mosfet like before.

Post all measurements. - You have done this already.

Power down -> remove the battery.

Attach only the power adapter. Measure the voltage on each of the pins of this battery mosfet...source; gate; drain.

[johnjohnjohnjohn]

Re: Troubles with HP pro x2 612 g2

G to D 12MOhms
S to D 25Mohms
G to S infinite

[johnjohnjohnjohn]

Re: Troubles with HP pro x2 612 g2

uh uh....
11.8 at DRAIN
0.18 at SOURCE
0.2 at GATE ....

[johnjohnjohnjohn]

Re: Troubles with HP pro x2 612 g2

do I.... get it... ?

[johnjohnjohnjohn]

Re: Troubles with HP pro x2 612 g2

does it mean bq24780s is failing ?

[mon2]

Re: Troubles with HP pro x2 612 g2

This is ok since this battery mosfet is required to be OFF when the adapter is ON.

Only one power source to power the logic board.

Attach the battery and the adapter. Power up again and measure the same voltage pins.

Post the readings.

The issue may be that the charger IC is not detecting the presence of the external adapter. More after your readings.

Wait..you are in France ? Does @Piernov make house calls??

[johnjohnjohnjohn]

Re: Troubles with HP pro x2 612 g2

i get the battery readings

[johnjohnjohnjohn]

Re: Troubles with HP pro x2 612 g2

S and D 8.3V
G at 14.3V
Nothing on dc mosfets aside the drains at 8.3V

[mon2]

Re: Troubles with HP pro x2 612 g2

Ok. That is not good. The battery mosfet is ON while the adapter is connected ? Can you confirm this understanding ?

Gate voltage is ENABLING this mosfet.

Update:

with extreme caution, measure the voltage on:

pin # 5 - ACOK
pin # 6 - ACDET