Dead LA-H323P (no light) - HP 15-DW

[Patan]

Need help here...
I'm new on the forum and I'm not professional in electronics so i ask sorry in advance for eventual errors...
As title says, i have a LA-H323P dead.

Now, little background.
The computer was working fine, just seems that the cable of screen was dying because it had the classic color problem, sometimes green, sometimes violet, sometimes perfect, but anyway working.
When i opened it the battery was so fat that was seriously near to explode.
So i removed the battery... and turned on the notebook... that was, again, working perfectly fine.
In the same time i started to measure the voltage in the LVDS pins just to check that everything was ok before buying new cable, just to be sure that the cable was the problem and not to waste money and time.
Suddenly the pc died.
No light anymore, nothing.
If someone has any idea what the hell happened please let me know...

No light when plugged, no battery recharging light when plugged, not any light when pressing start button.
I checked the main power 19v and is present, everywhere.
Every sub power supply in the coil output has 0v, cpu, gpu, ram, all 0v, but their mosfets has 19v input from main power, just they are blocked.
Strange that the only coil that has value is on and is (SEEMS) the battery charging coil, that without battery has around 3v and if battery is plugged has battery voltage (11.5v).
I went to check for the chips that gives 1v, 3v, 5v.
In all of these, the input 19v is present.
In 3v chip and 5v chip, enable pins (pin 12 and pin 6 respectively), receives high signal (3 volt like), but output (pin 6,19,20 and pin 2,12 respectively) is 0v...
In 1v chip, enable pin (pin 11) is 0v, and the output (pin 6,19,29) is obviously 0v.

NOTHING gets hot, even warm...

[rogfanther]

Most possibly, you shorted something when measuring voltages at the lvds connector.

[Patan]

Can you give me some starting points?
What can i check?
If necessary i have schematics and boardview (that I found here most likely...)

[reformatt]

I had something similar last week with a HP 15-DA (LA-J951P) after customer did a LCD and cable swap. Pretty sure he did this with battery connected given the damage to the board.

At a glance, the design is identical in respect of EDP connector and +3V power so I'm guessing you'll have a similar result.

This machine had +19V after the first two mosfets but no light on the charger (this comes from the EC). The +3VL LDO voltage was missing but not shorted. However the +3VALWP was dead short to ground, and this was traced to the PCH. Game over.

Most designs have +19V power on the very end of the connector to prevent this kind of SNAFU. But this one has it in the middle of the connector, with +5VS_TOUCH and TS_GPIO on either side. It's likely in your case and mine, that +19V was shorted into the TS_GPIO data line (which goes to the EC). This in turn killed the +3V converter and blew the PCH.

TLDR; Check PU301 pin 17 for +3V, and also PL302 resistance to ground.

[Patan]

PU301: 0V
PL302 11ohm
What next?...

[mon2]

See attached. Need to review the DCin mosfets & PUB1 charger IC that drives these power path mosfets.

Carefully, measure the voltage to ground of the DCin mosfets:

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

Measure the above for PQB11 and then PQB12 and post all measurements.


PUB1:

REGN ; pin 16
ACDET ; pin 6
VCC ; pin 20

[Patan]

PQB11
PIN 1-2-3: 19,6V
PIN 4: 25,5V (?)
PIN 5-6-7-8: 19,6V

PQB12
PIN 1-2-3: 19,6V
PIN 4: 25,5V (?)
PIN 5-6-7-8: 19,6V

PUB1
PIN 6: 2,65V
PIN16: 6,05V
PIN 20: 19,4V

[mon2]

These are good measurements and so far, the charger IC is working as it should.

Confirm the voltage to ground of:

ACOK ; pin # 5
SDA ; pin # 8
SCL ; pin # 9

PU301: 0V

Anytime a voltage rail is @ 0 volts or is lower than expected, remove all power -> meter in resistance mode -> measure the resistance to ground to confirm there is no heavy or shorting load on that power rail.

Confirm the resistance to ground of PU301 (pin 17) = LDO output for the +3VLP rail that is required for operation.

[Patan]

ACOK ; pin # 5 0V
SDA ; pin # 8 not simple to measure to ne honest, between 20mv-50mv
SCL ; pin # 9 kind of similar to pin 8, 20mv, near to 0v

[reformatt]

PU301 pin 11 should be about 4.4V (ENLDO_3V5V) , and pin 17 (or PC310) should 3V. This LDO output drives the EC.

11 ohms on +3VALWP lines up with my first post. The PCH was shorted but rose to 4 ohms or so after voltage injection.

[Patan]

Just to be sure, which is the PCH?
What do you recommend me to do?

[reformatt]

Take the heatsink off the CPU, the smaller of the die's is the PCH (Platform Controller Hub). Pro's use 1V voltage injection and thermal camera to locate the source of the (partial) short. If you don't have a thermal camera, you dab isopropyl alcohol (IPA) on the PCH and do the voltage injection. When voltage is applied you'll see the IPA evaporate quickly. Since you have 11 ohms, 1V may not be enough (only about 100ma), so you may need to go to 3V.

Confirm the other readings first with the LDO and the EC.

[mcplslg123]

Seems like a shorted PCH+EC scenario.

[Patan]

So, just to recap your theory:

LVDS 19V bridge to TS_GPIO
↓
TS_GPIO brings 19V and kill the EC
↓
EC killed PU301 3v chip
↓
PU301 3v chip killed the PCH

At this point, my only hope is that it's not the pch that's resisting and that there's something else shorted, right?
Where exactly can I inject the 1V/3V?

[reformatt]

Yes that's my logic. Inject at the coil PL302.

[Patan]

I injected 1v-3v but nothing, so the desperation to know what is going on here made me put a little bit more... 4V around...
Just on highest voltages around 3.5V-4V i BARELY SEE a little bit of alcohol moving... not at all fastly...

[reformatt]

11 ohms will only amount to around 270ma with 3V. It's not a huge amount as far as heat generation goes so can be hard to spot. The idea is to put a liberal amount of IPA on the part, and momentarily apply voltage injection. You will see some change in the way the IPA is evaporating if that is the part that is faulty.

I use a TS-30A 'short killer' (which is really a dumb name TBH) in conjunction with a thermal camera. What this device does over a conventional power supply is pulse the output on and off. This protects the PCB, since driving amps into a shorted component will produce heat. Makes it easier to spot on a thermal camera because the shorted component is now flashing like a beacon.

Not a great idea to push 4V into a 3.3V rail. Usually voltage injection does not exceed 1V, because a shorted component can possibly be feeding something that is running a much lower voltage.

[mon2]

TS-30A 'short killer' (which is really a dumb name TBH)

G'day mate. Next shift has started. Time for some Netflix.

[Patan]

I know it wasn't a good idea but I had no alternative, I overdid the voltage because I couldn't see the alcohol evaporate from the PCH and this board becomes more and more like garbage as I don't understand what the problem is.
In any case I was under 4v, around 3.8. but even so I'm not sure if the PCH is heating up.
The drying alcohol should be visible... I had never tried it on a PCH but it seems very little to me. could it be something else?

[reformatt]

G'day mate. Next shift has started. Time for some Netflix.

I cancelled that ages ago. I won't even bother till Hollywood stops making this PC/woke garbage they seem pre-occupied with.