Troubles with HP pro x2 612 g2

[johnjohnjohnjohn]

Re: Troubles with HP pro x2 612 g2

ok, first here is the adapter photo :

[johnjohnjohnjohn]

Re: Troubles with HP pro x2 612 g2

the nintendo switch adapter can only do 5 and 15V, I tried to plug it, nothing happens and i read 5.3V at the two usb c V pins
I tried with my Mii 11 phone adapter, it can go up to 20v (but with a weak 1.35A) but it doesn't even negociate.

[mon2]

Re: Troubles with HP pro x2 612 g2

Only if you feel comfortable, consider to use your external lab power supply to mimic the power adapter.

To do this, disconnect the external Type C power adapter.

Now the TPC8120 mosfets will remain off.

Dial up your DC power supply to 12v @ 3A (current limit it to this value).

Ground to ground.

Red power lead to the DCin mosfet (first mosfet where you measured the 0 ohms to the TPC8120 mosfet).

While the TPC8120 remains OFF; you will inject this external power supply feed.

With this condition, the ACDET should go HIGH -> charger IC should turn ON the 2 x DCin mosfets and power the logic board.

Test with and without the battery if you proceed. In theory, the battery should also charge under this setup.

Have to wolf down a late breakfast and then fix some blinds (they are not the LG brand) - BBL.

[johnjohnjohnjohn]

Re: Troubles with HP pro x2 612 g2

I injected 11.83V on the first dc mosfet drain, the same 11.83V that can be read when the board is power with the usb c charger.

When current is applied, the port led blinks as it does when plugged on dc, but then turns off, and the logic board too.

[mon2]

Re: Troubles with HP pro x2 612 g2

That bytes.

See attached on the ref design of the charger IC.

Locate the other mosfets on your board that are the high and low side for the battery charging.

These are mosfets Q4 (high side) and Q5 (low side) in the attachment.

Respectively, they will be connected to pin 26 and 23 on the charger IC.

Once you locate the mosfets, post a pic of the parts. Remove all power and measure their resistance across the pins, as you have done before.

We are checking if perhaps the high side mosfet is leaking. Check even the low side mosfet.

Post your measurements.

[johnjohnjohnjohn]

Re: Troubles with HP pro x2 612 g2

hi, ok
So first of all, in the photo 2 you ll see that the pin 26 goes, it seems, to the intersil IC (photo 3) :

I read resistance values coming from pin 26 of bq24780s on many, many pins of this IC
I can't find any datasheet for this IC.

I can't find where pin 23 goes. It directly sink into the board... I didn't find any track of it

Pin 26 gives reading on these components around BQ24780S (see first photo) : K727, A7W,
L43 (x2), SBI, NM742 (below SB)

[mon2]

Re: Troubles with HP pro x2 612 g2

Search for mosfets with 8 pins like before.

[johnjohnjohnjohn]

Re: Troubles with HP pro x2 612 g2

Ok,
The task is pretty hard... I have readings from pin 26 on almost every 8 pins mosfets I found... ! How can I proceed ?

[mon2]

Re: Troubles with HP pro x2 612 g2

See the ref schematic. The mosfets will be close to a coil (grey?). The mosfets will share common pins like schematic and probably near the battery connector since this rail charges the battery.

Post pics of mosfets that you find and their topside markings.

Assuming that they will be single package single mosfets like before.

[johnjohnjohnjohn]

Re: Troubles with HP pro x2 612 g2

These two mosfets might be the ones...

I marked them with a white Posca

What s your take on this ?

[mon2]

Re: Troubles with HP pro x2 612 g2

Perhaps. Remove all power.

Meter in resistance mode.

Check the resistance from the grey coil to the battery connector where you saw the red wires. Do not connect the battery. Measure only at the battery connector on the logic board.

The resistance should be ~0 ohms if the coil is the correct one. The mosfets we wish to measure will be connected to the same coil.

[johnjohnjohnjohn]

Re: Troubles with HP pro x2 612 g2

the resistance is 0 on the red wires corresponding pins. In fact it is the only one with 0 resistance.

[mon2]

Re: Troubles with HP pro x2 612 g2

With meter in resistance mode. No power / no battery.

Place one meter probe on the connector where the battery red wires end up on the logic board.

Place other meter probe on the nearby coil you can find.

If you read ~0 ohms on this test, then the coil is linked to the battery charging.

Confirm the part and location if you find this measurement to be ~0 ohms.

[johnjohnjohnjohn]

Re: Troubles with HP pro x2 612 g2

Indeed, the grey coil, just beside the G8 VUD mosfet, is the only one showing 0 Resistance to the three red battery pin

[mon2]

Re: Troubles with HP pro x2 612 g2

Perfect. Now review which side is the source (pins 1-2-3) will be shorted; pin 4 by itself; drain (pins 5-6-7-8) will be shorted - for each of these mosfets.

Then proceed to continue to test the resistance across the mosfet pins:

source (1-2-3) & drain (5-6-7-8)
source (1-2-3) & gate (4)
gate (4) & drain (5-6-7-8)


Post the readings of each measurement.

Then repeat for the next mosfet that is also connected to this coil.

One mosfet = high side.
Other mosfet = low side.

These 2 mosfets & the coil you have found are responsible for the battery charge voltage. Each mosfet pulses ON / OFF till the ideal charge voltage is in range for your target battery pack. This is a BUCK regulator and accepts the high input voltage (12V in your case) and lowers it to a safe value for the battery pack.

The LOW side mosfet will have ~0 ohms resistance to ground on likely the source (pins 1-2-3).

[johnjohnjohnjohn]

Re: Troubles with HP pro x2 612 g2

left mosfet on the photo (7506 GA 712H)
Source to Drain 1050KOhms
S to G 230K
G to D 1500K

Right mosfet (G8 VUD 71Z04) It has 0 resistance to ground on its source
S to D 12.8K
S to G 195K
G to D 216K

[mon2]

Re: Troubles with HP pro x2 612 g2

Right mosfet (G8 VUD 71Z04) It has 0 resistance to ground on its source
S to D 12.8K

This measurement looks very low.

Do you have hot air tools (flux / tweezers / hot air station) to remove this mosfet so that it can be tested out of circuit ?

When the mosfet is out of the circuit, the same S-D resistance should be checked once it is cool to do so.

[johnjohnjohnjohn]

Re: Troubles with HP pro x2 612 g2

yes, i remove it right away, let's see

[johnjohnjohnjohn]

Re: Troubles with HP pro x2 612 g2

ok, so
probing the empty traces :

S to D keeps climbing over 500KOms
G to S about 200KOms
G to D keeps climbing over 500KOms

I took the tiny mosfet and probed it for resistance. It s almost 0Ohms Source to Drain

[mon2]

Re: Troubles with HP pro x2 612 g2

Ok - back from the never ending shopping for groceries...

1) Measure the resistance on the pins of the actual mosfet you have removed (not the PCB pads). We want to check if the removed mosfet is leaking / defective without influence of the other parts on the logic board.

Post each measurement.

2) Which tiny mosfet ? Can you post a pic ? What are the top side markings ?