HP 15-ac126nv no power at all

[Andreasbest]

Re: HP 15-ac126nv no power at all

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[mon2]

Re: HP 15-ac126nv no power at all

1) What is the resistance to ground of pin # 15 of PU2 ?

The new resistance to ground on this LDO rail may be ok since the rail can supply upto 175mA.

I = V/R
= 3/68
= 0.044A = ~44mA

2) What is the resistance to ground of pin # 14 on PU2 pads ?

3) What is the resistance to ground of pin # 16 ? This is the pin with the PQ8 mosfet.

4) You can try to use the removed PU2 back onto the logic board and check if PU2 heats up or not.

Before you solder the parts back, confirm again that there are no very low resistance readings for the PU2 PCB pads.

[Andreasbest]

Re: HP 15-ac126nv no power at all

1) pin # 15 is the one i measured all this time, confused to be 16. Resistance is 70Ω
2) Infinite
3) Infinite
4) PQ8 is still desoldered, want to resolder PU2 even if resistance @ pin 15 is still low @70Ω?

[mon2]

Re: HP 15-ac126nv no power at all

According to the above earlier calculation, the current consumption is ~44mA if the resistance is ~70 ohms. That is ok for this rail since it can support upto 175mA.

Perhaps PU2 is damaged and therefore will heat up like before or perhaps it will be ok now that the excessive loads are removed. If you have a fresh part for PU2, consider to solder it onto the PCB. If not, proceed with the older PU2.

Again, before soldering back PU2 - no other pins are with a low resistance to ground on this part ?

[Andreasbest]

Re: HP 15-ac126nv no power at all

Confirmed, no other pins with low resistance.
Now i have a new PU2 but PQ8 is still desoldered, do you want to solder PU2 and power it on without PQ8?

[mon2]

Re: HP 15-ac126nv no power at all

Suggest to solder in the new PU2 and also the PQ8 dual mosfet.

Then, without power, measure the resistance to ground of each pin on PU2 to check for any low resistance readings.

[piernov]

Re: HP 15-ac126nv no power at all

Low resistance to ground on LDO3 is never fine.

[Andreasbest]

Re: HP 15-ac126nv no power at all

I solder back everything (new PU2, old PQ8) still no power and again PU2 hot.
Resistance on pin 15 = 4Ω again, with or without PU2 soldered
What do you think?

[mcplslg123]

Re: HP 15-ac126nv no power at all

Wrong approach. When resistance on LDO3 is low, it indicates problem downstream and if you replace mosfet/pwm without solving low resistance, they will burnt again and again and may further reduce the chances of repair.

Take a fresh approach, Desolder both PU2/PQ7. I'm still wondering why you removed PQ8 as its connected to +5VALW line and not +3VALW. Measure resistance(while PU2 & PQ7 are removed) on Pin14(LDO5) and pin 15(LDO3).

If the resistance is still low on any of these LDO, you may need to inject 1V/5A on that line to find out what is wrong.(Voltage shouldnt exceed 1V).

Very likely KBC and/or PCH part of SOC will heat up. Update us about ur findings.

[Andreasbest]

Re: HP 15-ac126nv no power at all

Thank you very much for the reply, i believe the problem is on KBC as there was the liquid damage i mention before, good thing is that it can be replaced easy as the pins are exposed on the sides and not underneath.

I will do exactly what you told me on Monday, i'm away from the lab for some days and i'll inform you.

[mcplslg123]

Re: HP 15-ac126nv no power at all

Just a reminder, KBC has to be programmed after replacement but first findout whether its bad kbc or not.

[Andreasbest]

Re: HP 15-ac126nv no power at all

Wrong approach. When resistance on LDO3 is low, it indicates problem downstream and if you replace mosfet/pwm without solving low resistance, they will burnt again and again and may further reduce the chances of repair.

Take a fresh approach, Desolder both PU2/PQ7. I'm still wondering why you removed PQ8 as its connected to +5VALW line and not +3VALW. Measure resistance(while PU2 & PQ7 are removed) on Pin14(LDO5) and pin 15(LDO3).

If the resistance is still low on any of these LDO, you may need to inject 1V/5A on that line to find out what is wrong.(Voltage shouldnt exceed 1V).

Very likely KBC and/or PCH part of SOC will heat up. Update us about ur findings.

Hello
Pin 14 infinite resistance
Pin 15 same as before 6Ω

Inject time?

[harshana]

Re: HP 15-ac126nv no power at all

Hello
Pin 14 infinite resistance
Pin 15 same as before 6Ω

Inject time?

Yes Its time to inject as mcplslg123 said. waiting to see the progress. afraid about pch.

[Andreasbest]

Re: HP 15-ac126nv no power at all

Pin 15 Red
GND black
(Just to confirm) Correct?

[harshana]

Re: HP 15-ac126nv no power at all

Pin 15 Red
GND black
(Just to confirm) Correct?

Yes. also keep that on your mind, you should not increase voltage no more than 1v. I suggest you to start from 2A and increase. Try to find out the guy who is heating.

Edit: Make sure PU2 and PQ7 remove from the board before inject

[Andreasbest]

Re: HP 15-ac126nv no power at all

I'll use the thermal cam, it will be easier this way

[harshana]

Re: HP 15-ac126nv no power at all

I'll use the thermal cam, it will be easier this way

Sounds great. lets see

[Andreasbest]

Re: HP 15-ac126nv no power at all

Weird situation here and i'll explain
Applied only 1v 2a as you suggested, mb draw only 0.22A for some seconds then only 0.0011A, i checked resistance again and now it's 1.7KΩ.
Now what?

[harshana]

Re: HP 15-ac126nv no power at all

Weird situation here and i'll explain
Applied only 1v 2a as you suggested, mb draw only 0.22A for some seconds then only 0.0011A, i checked resistance again and now it's 1.7KΩ.
Now what?

as mcplslg123 said, you can increase upto 5A. try to increase little bit like 3A or 4A. Anything changed???

[Andreasbest]

Re: HP 15-ac126nv no power at all

I tried it no change, still getting onlily 0.0011A and resistance 1.7kΩ