HP ENVY NOTEBOOK - 13-D006NA (MOBO. LA-C482P REV. 1.0) Not Working - No Lights

Hello Everyone,
I am looking for your help to identify the problem:
HP ENVY NOTEBOOK - 13-D006NA
MOBO. LA-C482P REV. 1.0
I was repairing the same model some time ago and this one did look like similar fault but it is not.
Thermal camera did show PU302 overheating. I have replaced PU302 but nothing has changed.
Overheating stops when PJ304 is open. This way I have followed path for +5VL and took me to US3 IC.
I have removed US3 and closed PJ304 but overheating has come back. Thinking US3 is causing this was wrong.
When PJ304 is closed 5V is dragged down to 4.8V and PU302 is overheating.
What could be the cause of it please ?
Thank you.
Best Regards,
Rafal S.

Hello!

Inject 5V from the laboratory power supply to "+5VL" power rail (pin 1 of jumper PJ304) and specify the electrical current that flows from the laboratory power supply during the test.
The jumper PJ304 should be opened during the test.

Hello Matic,
Would voltage injecting make sense when US3 is removed ?.
I did not solder US3 back. Small piece of IC was broken during removal. I am waiting for replacement to be delivered.
It will take some time to be delivered (purchased from China).
Thank you for your support as always.
Regards,
Rafal S.

Try the same injection of 5v on + 5VL (even with US3 removed).

Hello Machine,
Thank you for your reply. I have applied voltage as advised.
5V to pin number 1 when jumper PJ304 was opened and is drawing 0A.
Not even partially shorted. After test was completed I did connect power cable.
I have measured voltages on both sites open PJ304:
Pin 2: 5V
Pin 1: 0V
After closing jumper:
4,8V
What can be causing voltage drop (from 5V to 4,8V) after closing PJ304 ?
Regards,
Rafal S.

Does the chip PU302 still heats up when the jumper PJ304 is closed?

Hi Matic,
Yes. Temperature goes to 70°C very fast. 2 seconds.
In general there is some strange power distribution in this model.
In PU302 from the same pin we have +5VLP and +5VL after jumper.
When jumper PJ304 is closed voltage imbalance is occurring.
Could problem be on site of +5VLP regardless the lack of PU302 overheating when jumper is open ?
Thank you.
Regards,
Rafal S.

Please, post a clear picture of PU302 chip area of the board and highlighted the point, where you injected 5V for the test.

Please see attached photo. It was top site of jumper.
This site was connected to one pin of US3.
I have checked it after US3 was removed and before voltage injection.

Set the meter to the diode test mode and measure the voltage drop to ground on highlighted point in your picture with both polarities of test leads. Make sure the battery and power supply are disconnected from the board during the measurement.

Check if the chip PU302 is soldered correctly - it seems a bit shifted/rotated.

Hi Matic,
I have measures highlighted point in diode mode as advised:
OL V - above scale
0.8 V and slowly raising (reversed polarity)
I have removed PU302 as soldered again - position has improved but no luck.
Closed the jumper and overheats the same.
From your experience would you say PU302 what I have replaced is faulty ?
Thank you.
Regards,
Rafal S.

Measure the resistance between points "A" and "B" highlighted on the following picture.

Hi Matic,
My apologies for late reply. I had a busy day.
I did measure resistance with PJ304 open and shows 0.21 Ohm only.
0,15 Ohm with closed PJ304. What is causing short here ?
Thank you.

Measure the resistances between listed pins of transistor US2:
a) Between pin 1 and pin 4
b) Between pin 1 and pin 8
c) Between pin 4 and pin 8

Hi Matic,
Assuming that pin 4 is a GATE resistance measurements are:
PJ304 was left open.
a) 0,9 MOhm and increasing
b) 6,0 MOhm and increasing
c) 5,5 MOhm and increasing

PJ304 was closed.
a) 1,8 MOhm and increasing
b) 1,7 MOhm and decreasing
c) 3,2 MOhm and decreasing

Remove the transistor US2 from the board and check, if the PU302 is still hot with closed jumper PJ304.

Hi,
US2 is removed and with PJ304 closed PU302 is not overheating anymore.
Is that mean transistor itself was faulty ?
Thank you.

RafiManch ha scritto:Is that mean transistor itself was faulty ?

No, probably not.

Check, if the machine works okay without this transistor and without chip US3.

Hi Matic,
Thank you for your time.
Still no luck. No lights and no power.
I have changed BIOS battery as old one was drained (0,19V only).
Would flat BIOS battery indicate Super I/O or PCH problem ?

Measure the voltage on new RTC battery and note the result.
Remeasure the voltage on RTC battery again after 1-2 days and specify both results.