HP 14-DV0021NH not turning on

[unimatrix93]

I'm trying to fix up this HP laptop with no power problem.

Power led does show white led as I plug in the charger but it doesnt react to the power key.

I connected it to my PSU and as I turn on the PSU, the board takes 30mA for a few seconds then it goes down to 5mA. Connecting the battery doesn't change the current only turn the white led to orange.

I checked all the coil on the motherboard and I found 1.3V and 5V but no other power rail were present.

Also, I checked on the bios IC (XMC QH128ahig) and it missing VCC.

[mon2]

Suggest to test with the original OEM power adapter for this unit. HP, like other brands, has an adapter detection circuit. HP uses an analog voltage on a dedicated pin on the DCin power jack. This voltage is sampled by an analog to digital converter to identify the power rating of the power adapter. A lab power supply will not offer this support.

Best to test with the original power adapter and then monitor the power path as per the articles above by piernov on charger circuits. Often the DCin mosfets are the fault.

[unimatrix93]

Suggest to test with the original OEM power adapter for this unit. HP, like other brands, has an adapter detection circuit. HP uses an analog voltage on a dedicated pin on the DCin power jack. This voltage is sampled by an analog to digital converter to identify the power rating of the power adapter. A lab power supply will not offer this support.

Best to test with the original power adapter and then monitor the power path as per the articles above by piernov on charger circuits. Often the DCin mosfets are the fault.

The funny thing, it worked perfectly fine with a Hama universal charger + HP DC jack adaptor.

Anyway I check on the DCin Mosfets anyway and report back.

[unimatrix93]

I checked the DC in mosfet and AONS36316 has a resistance between S-D is around 160 ohm. D-S is 170 ohm.
Isn't it a bit low?

Sorry, I identified it wrong: it's not the first mosfet from DC in. The DC in mosfets are probably okay.

[mon2]

Yes, the mosfet resistance is far too low for a normal component. Each should be hundreds of k ohms or higher. It is possible that the 2nd mosfet in the power path is defective. Test to confirm using the same method.

[unimatrix93]

Yes, the mosfet resistance is far too low for a normal component. Each should be hundreds of k ohms or higher. It is possible that the 2nd mosfet in the power path is defective. Test to confirm using the same method.

So I removed the MOSFET and also checked the mosfet next to it., that looks okay.

Now I removed the mosfet and I discharged it.
Now it has 4.2M ohm resistance S to D and OL D to S.

[mon2]

Need to also check

source to gate
drain to gate

[unimatrix93]

Need to also check

source to gate
drain to gate

gate to drain OL. MM is set to 200M.
gate to source also OL.

[mon2]

Mosfets look ok. Share a pic of the power cable that mates with the connector where you have soldered for your Dc power supply.

If available, link the schematic. Which charger IC is onboard this logic board?

What are the silk screen markings onboard? Post a pic.

[unimatrix93]

Mosfets look ok. Share a pic of the power cable that mates with the connector where you have soldered for your Dc power supply.

If available, link the schematic. Which charger IC is onboard this logic board?

What are the silk screen markings onboard? Post a pic.

Sorry for being late, lots of work lately.
There is no schematic for this board, at least I couldn't find a free one on the web.
The charger IC is an Intersil ISL9238.

There is no silk screen markings other than the model number and such.

[unimatrix93]

Still no progress on the laptop. I thinking about trying to charge it with an USB C charger.
The charger IC's DC IN pin has only 17.9V. Bit low isn't it?

[unimatrix93]

Turns out the first two mosfets has wrong gate voltage:
First mosfet has 6V and the second mosfet has 17V.
What could be the cause?

[mon2]

Share the topside markings of these mosfets or post clear pics of the same.

[unimatrix93]

Share the topside markings of these mosfets or post clear pics of the same.

I just realized that these mosfets are P-channel mosfets. So the lower Gate voltage is correct, no?

[unimatrix93]

Some progress:
I connected a HP adapter to my lab PSU and I plugged it in my notebook.
With battery, it does charge nicely: taking 220mA and slowly decreasing.

So the charging circuit and EC chip is probably fine.

Without the battery is does this and pressing the pwr button does nothing: