HP 15-ac126nv no power at all

[Andreasbest]

Hi!
Received a HP laptop today with small liquid damage and cleaned it up with isopropylene alcohol.

I noticed that PU2 ( RT8243AZQW ) gets extremely hot indicating a shortcircuit, should i replace it right away OR should i check something else first that perhaps causes the short and PU2 is good?
Schematics attached.

Thank you!

[mon2]

Re: HP 15-ac126nv no power at all

If the part is heating up more than normal then there is a fault.

Remove all power. Meter in resistance mode.

Check the resistance to ground of each output voltage rails on this component.

Post all measurements. If a reading is very low, then need to locate the reason. Perhaps this part is now defective from this event.

[Andreasbest]

Re: HP 15-ac126nv no power at all

I remove the PU2 and measure resistance to all pins, all look fine with high resistances to GND 10's ok kΩ except pin 16 that is only 6Ω.
Is that normal?

[mon2]

Re: HP 15-ac126nv no power at all

No - that is a very low resistance.

Remove the capacitor @ PC213 and measure again.

[Andreasbest]

Re: HP 15-ac126nv no power at all

There is no boardview available so i removed the capacitor that is connected next to pin 16.
Short remains on both sides.
Uploading picture before and after.

[mon2]

Re: HP 15-ac126nv no power at all

Then remove diode PD202 - make a note of the polarity on the diode for replacement.

Check again.

[Andreasbest]

Re: HP 15-ac126nv no power at all

Could please tag it? I can't find it.

[mon2]

Re: HP 15-ac126nv no power at all

Post a clear pic of the area - should be black in color and with a band (white stripe) on it.

[Andreasbest]

Re: HP 15-ac126nv no power at all

Found it and desolder it, 7Ω remain on pin 16

[Andreasbest]

Re: HP 15-ac126nv no power at all

Uploadding pictures of the liquid damaged area, perhaps theey can give us a clue before voltage injecting : )

[Andreasbest]

Re: HP 15-ac126nv no power at all

I resolder both the cap and the diode and now the resistance is 30Ω
How is that possible?

[Andreasbest]

Re: HP 15-ac126nv no power at all

Plus multimeter doesn't indicate any connection between PD202 and PC213

[mon2]

Re: HP 15-ac126nv no power at all

Wait! My bad - have too many open Windows.

Let us back track. Keep note of each part that is being removed so you can replace it back. The ECE is not the area of interest.

Pin #16 of PU2 is linked to a mosfet device @ PQ8. It should be 8 pins.

Remove this dual mosfet @ PQ8 and test the resistance again on pin # 16.

Update:

In my earlier review - searched for 'PU2' and stopped @ 'PU201' and referenced the pin #16 = REGN pin on it. My apologies.

[Andreasbest]

Re: HP 15-ac126nv no power at all

"In my earlier review - searched for 'PU2' and stopped @ 'PU201' and referenced the pin #16 = REGN pin on it. My apologies."

Sorry but i don't got it, should i procced as you told me with PQ8 or not?

[mon2]

Re: HP 15-ac126nv no power at all

Yes - remove PQ8 (8 pin device). Take a picture of the topside for the replacement / pin # 1 orientation.

[Andreasbest]

Re: HP 15-ac126nv no power at all

With PQ8 removed i get 68Ω

[mon2]

Re: HP 15-ac126nv no power at all

Let me understand where we are at...

you have PQ8 removed ?
you have PU2 removed ?

but you are measuring 68 ohms to ground on pin #16 of the PU2 pcb pad ?

This is not a good reading. The reading should be OL since there is nothing on pin # 16 of PU2 if it is removed.

Can you confirm the details ?

[Andreasbest]

Re: HP 15-ac126nv no power at all

Exactly.
PQ8 and PU2 removed now, resistance between pin 16 and GND = 64Ω

[mon2]

Re: HP 15-ac126nv no power at all

That does not sound right - is the posted schematic 100% for your laptop ?

[Andreasbest]

Re: HP 15-ac126nv no power at all

Just found the mistake
I count the pins clockwise while they are counter clockwise like usual.
I'm terribly sorry for this.

The correct pin is 15, not 16 : (