Troubles with HP pro x2 612 g2

[johnjohnjohnjohn]

Hello everybody
I've got big troubles here with an HP pro x2 612 g2

When I plug the charger, nothing light up, and the tablet/laptop doesn't detect it at all, or at least no orange, white, blue or any color led beside the port. Windows doesn't detect it too.
BUT
If when off, I unplug the battery inside (back shell is removable with only finger nail like some smartphones) then the charger is recognized, charging port led lights up, and the pc works like this, everything is "fine".
I tried carefully to plug the battery when pc already on on AC. It then recognise it and start charging it !
If I then unplug the charger, the pc turns off and stops instantly to recognise or react to the charger. The pc then use the battery instead, doing as if not charger was plugged in.
When I'm able with this "hack" to charge the battery, and i then use the PC on it, I checked battery health and it say only 10% wear. The battery is not swollen at all, I made a visual inspection.

As the charging port works when it's plugged without battery installed, I supposed it could not be a port issue ?

Any help is greatly appreciated. Thanks

[mcplslg123]

Re: Troubles with HP pro x2 612 g2

There should be dc-in mosfets located near to charging port. measure resistance betwwen Source-Drain
Source-Gate
Gate-Drain
on both of them. Resistance should be measured without any power(Adapter+Battery) connected. Meter should be set to 200K or higher.

[johnjohnjohnjohn]

Re: Troubles with HP pro x2 612 g2

Thank you for your time. I think i get the idea, if i have troubles identifying the mosfets, I ll post pictures. It s a tiny board !

[johnjohnjohnjohn]

Re: Troubles with HP pro x2 612 g2

Hi
I m unsure of what to mesure. Here is photos of the two side of the usb c charging port

I also removed the giant heatsink that covers almost all the motherboard. I can't figure out which chip could be the one managing power between battery, dc port and the computer itself

A big thank for your time

[mcplslg123]

Re: Troubles with HP pro x2 612 g2

So the system is powered by USB-C and not dc jack. Perhaps @mon2 is better equipped to help you out.

[johnjohnjohnjohn]

Re: Troubles with HP pro x2 612 g2

I guess i'm stuck here. There are no schematics or boardview avalaible. I have no clue which chip controls the power priority between usb c dc in and battery. I ve never had such issue before. All the computers I've worked on so far had standard dc jack. Well...

[mon2]

Re: Troubles with HP pro x2 612 g2

Yes, it may be a challenge to work without schematics but let us review what we can.

Locate the usb type c connector.

This connector is an industry standard and will match the pinout of the specification.

Take and post a clear picture of the solder side where we can count the # of contacts for this part.

Then once we know the connector we are up against, we can take some measurements. The usb type c port on this logic board will a power delivery model.

When you dock the adapter, the adapter will broadcast upon demand of the usb c controller, a list of power delivery contracts. Each contract will consist of a voltage and current pair.

The usb c controller will then select the most suitable contract to power this logic board.

This communication is over the CCx pins. There is CC1 pin one side of the type connector and there is CC2 on the other side. This way, it does not matter which side is inserted on the adapter, the logic board can read the power delivery contract list.

You may just have a physically defective type c connector but you mention the adapter works if you use the combination of the adapter and battery and a pinch of black pepper over the shoulder. I think the connector is ok at this time.

Locate near the connector, the usual black in color 8 pin mosfets. They act like solid state relays or switches.

Read off the markings from their top side. We need to learn if they are N-channel mosfets or P-channel mosfets.

Remove all power. Meter in resistance mode. Pick any resistance scale.

Using the meter, place one probe on pin #1 and the other probe to pin#2. The resistance should be ~0 ohms.

Now move the probe to pin #3 (from pin #2). Should still be ~0 ohms. Then finally to pin #4. Shoud NOT be ~0 ohms. Confirm it. We are trying to.learn, which pins are the source, the gate and drain pins.

Pins 1-2-3 will be shorted. Pin 4 will be isolated.

Pin 5-6-7-8 will be shorted.

Review the above so we know where is pin #1 and then we can take other resistance checks to debug this board.

Often, one of these mosfets gets killed from transients or other events and need to be replaced as it is leaking... conducting when it should be OFF.

[johnjohnjohnjohn]

Re: Troubles with HP pro x2 612 g2

thank you for your time ! I do that right away ! You re giving me hope

[johnjohnjohnjohn]

Re: Troubles with HP pro x2 612 g2

So, I mesured the mosfet located beside the usb c port (7400A) as I understand, the gate is the pin isolated on it s own trace (4 then ?), while the source is the three pin beside (1-3 ?) and the drain is the four pins on the other side, grounded. Right ? So, the gate has infinite resistance against the seven other pins, 1 to 3 are shorted, 5 to 8 shorted too. 1 to 3 have infinite resistance against 5 to 8. I guess then that this mosfet is good ? Sorry for my English, always easier to understand than explaining with it. I also checked the two mosfets near the BIOS chip Winbond : TPCA 8120 the two are seemingly good, exept that the gate has 50KOhms resistance with 1 to 3 instead of infinite. I don't know if it means anything.

[mon2]

Re: Troubles with HP pro x2 612 g2

Hi. In the received cloud posting of additional pics, found the charger IC.

It is the TI 24780S - locate it as it is near the edge of the PCB.

Focus on this area - this is the battery charger IC that decides when the adapter or battery are to power this logic board.

We will assume that the USB Type C controller is working and is able to select a suitable power delivery contract. In the end of this negotiation, the voltage is enabled from the external adapter to power this board.

Then this charger IC steps into the equation to enable / disable the local mosfets.

Likely one of the N-channel mosfets near this battery charger IC is defective.

First locate this part and inspect the 8 pin mosfets. The appear to be from Alpha-Omega.

See attached.

Next, we need to review the pinout of the 24780S and very high probability that this design will be close to the reference design from TI.

Then need to confirm which mosfet is which (see the yellow arrows) and how they connect to this charger IC.

Pin # 4 will be driven by the ACDRV pin of this charger IC. Often there are 2 mosfets for this purpose - they are the suspected parts that may be damaged. Likely at least one is defective / leaking.

update:

1) attached the datasheet for this charger IC

2) attached a reference design schematic for this charger IC - your logic board will be very similar to this one

3) remove all power -> locate the ACDRV pin on this charger IC -> meter in resistance mode (20k or higher) probe on this pin -> locate the mosfet(s) with the yellow arrows -> other probe on pin # 4.

What is the resistance ? We are trying to locate the GATE pin of the 2 x DCin mosfets that are driven by this ACDRV pin.

The resistance should be ~4k between the ACDRV and the 2 x DCin mosfets (gate pin # 4).

Once they are found -> need to check the resistance of these mosfets with the meter (NO POWER when checking resistance).

[johnjohnjohnjohn]

Re: Troubles with HP pro x2 612 g2

The two E6 GUD 6T1H07 (the two top on the photo) PIN 4 are connected to the acdrv
Indeed the resistance is 4KOhms on both
I'm learning a lot here !

[mon2]

Re: Troubles with HP pro x2 612 g2

Ok. So now you have located the 2 x DCin mosfets.

Still with no power to the logic board, continue to check the resistance across the pins of these mosfets as follows.

Meter in any scale (to start).

Check the resistance between:

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

If the meter reports '1' or 'OL' (over limit) -> switch to a higher resistance scale to get your measurement.

We are checking for a low resistance across the mosfet pins which often means the mosfet is leaking / defective.

Post your measurements for each of these 2 mosfets you have found.

[johnjohnjohnjohn]

Re: Troubles with HP pro x2 612 g2

i do it right away. In the meantime, among old mainboards I keep "just in case" I found one with a bq24780s. So if needed, maybe...

[johnjohnjohnjohn]

Re: Troubles with HP pro x2 612 g2

ok, so
infinite resistance for all mesurements
Of course, pins 4 of the two mosfet are continious together, same for the 1-3 of the two

[mon2]

Re: Troubles with HP pro x2 612 g2

Can you post a pic of your meter during these tests ? You should have some value but not all should be so high.

What resistance scale is being used for the measurement ?

[johnjohnjohnjohn]

Re: Troubles with HP pro x2 612 g2

200K ...
Ok, i do it again with a better multimeter. Bear with me, because this better multimeter has huge probes. I do it now.

[johnjohnjohnjohn]

Re: Troubles with HP pro x2 612 g2

the bottom one has 412KOmh between source and drain
the top one (alway according to the photo orientation) has above 1MOhms

[johnjohnjohnjohn]

Re: Troubles with HP pro x2 612 g2

I really need to sharpen this probes.

[mon2]

Re: Troubles with HP pro x2 612 g2

Post the readings of each in a table for:

source (1-2-3) & drain (5-6-7-8) - what is the reading ?
source (1-2-3) & gate (4) - what is the reading ?
gate (4) & drain (5-6-7-8) - what is the reading ?

then repeat for the next mosfet.

[johnjohnjohnjohn]

Re: Troubles with HP pro x2 612 g2

ok, even if the reading is in the MOmhs range ?