HP 13-ad017nc - doesn't start

[YellowJacket]

Hi all,

I got this laptop to fix, this is known history - firstly, laptop had some troubles with turning ON ( turned on at third attempt, or so ). Then, during windows installation, USBs were not working at all ( it was unable to detect any USB flash stick ). Even after installation and looking for some drivers. Then a guy told me, he tried to install some software ( from last conversation, it should be "any desk" software ), and during installation the laptop shuts down. From that moment, it doesn't turn on. After connecting the charger, there is no light on charging port ( as it should be I suppose ), but an LED on the power button is turned on permanently. Still no reaction when I press it. Battery connector is ripped off of the board, so I am working without battery ( will fix it in case, I repair the board ).

What I discovered already:
- 5V power rail had too small resistance; I found damaged IC --> TPS2546 along with a ferrite bead connecting the IC and the USB port. After removing them from the board, resistance of 5V power rail raised up to kohm range
- I tried 3 different BIOS firmware, one found somewhere here on badcaps, and two repaired ones ( from discord, thank you guys, if you read this ). Laptop acts the same, with all firmware, even with removed EEPROM IC

Since I have no schematic ( requested here, but no luck so far ), or board view, I have no idea, how does power sequence look like here. So I don't know, what to check. From my view, it looks like EC is not responding. Or I got hint, that one of the coil has too low resistance to ground, even if it has voltage ( the one with 1.4 ohm ), but again, I have no idea, what power rail it is. So maybe dead PCH too.

I would be thankful, if anyone of you can help me, how to confirm dead EC/PCH, or just where to start. For now, I am not going to fix USB, because well, it has no sense in this state. Thank you in advance, and if you need any other info, let me know.

[YellowJacket]

Thank you, piernov. Actually, you hit the jackpot. Amazing deduction!

I tried to hook a PSU on the LDO 3.3V output ( even, if there is kohm range ), and current consumption was around 300 mA. And no, it was no EC. There was two schottky diodes in its way, and behind second diode was like zero point something resistance to ground. Injection of 0.9V at that point heated up PCH in up-right corner of its crystal. So yeah, nice to meet you, donor board.

I only wonder, if this was just random failure, or the customer did something ( he previously wanted me only to fix the USBs - messing with USBs can fry PCH ) and he caused it all. Anyway, thank you all guys for your support and patience, I wouldn't made a single step without your clues. Take care, see you next time.

[mon2]

Hi.

1) apply the best bios available to you for this board.

2) attach the power adapter. Locate the dcin connector and nearby will be the dcin mosfets. Post their top side markings or better if clear pics can be taken. The charger ic will also be nearby and will be a square black ic. Which charger ic is onboard?

Do you see any LEDs turn on the board? Led blink sequence?

What is the voltage to ground starting the dc adapter input connector? Meter in DC volts scale of 30v or more. Red probe on point to measure. Black probe to ground (metal shield is ok).

[YellowJacket]

Hi mon2

1.) I flashed there original bios dump, after cleaning its ME region. As I mentioned, the laptop behaves always the same though. If you think, it is bios related, let me know, I will ask here on badcaps for another dump

2.) First DCIN mosfet is AON6428, second mosfet is AON7414. Charger IC is BQ738


- about LEDs : the one on the charging port, it is all time turned off. Then, there are three LEDs under power button. These LEDs are meant to shine together I believe, and this power button lights all the time, from the moment I connect the charger. No other LEDs on the board

- there is 19.9V on drain of both mosfets, same voltage for source of both mosfets. 25.66V on gate of both mosfets

[mcplslg123]

Dc-in fet biasing is correct. Absence of light on dc jack is almost a sure indication of missing 3V LDO rail. Locate your 3V regulator,check datasheet if available and check 3V LDO is present or not. If not present,check resistance to GND on 3V LDO.

[YellowJacket]

Thank you mcplslg123 , you gave me really difficult task though.

I tried to analyze the circuitry as much as I could, and I looked around both 5V coils and the 3.3V one. But all three had nearby an IC, which was hard to find datasheet of. First picture is an IC connected to 5V coil on the left ( from picture in first post, 3k5 resistance ). Second picture is an IC connected to 5V coil on the right ( 22R5 resistance ). Third picture is an IC connected to 3.3V coil ( 3k3 resistance ).

Anyway, I was able to measure 3.3V on one capacitor nearby EC. On the another two nearby I was able to measure 2.9V. Sadly, EC has SMD package, so no way to figure out, where is 3.3V LDO going into it. So now, I am trying to find out some datasheet of these three ICs and get some info, if any of these have LDO regulator integrated. Feel free to lead me, if you have any other idea, what to check. I am really helpful for any of your hints, guys. Absence of schematic for this particular board makes it so tough to fix for me.

[SMDFlea]

The 1st chip is a Silergy,the other 2 are Monolithic Power .You`ll find all 3 marking codes in the IC Marking Codes sticky thread -> https://www.badcaps.net/forum/troubl...and-datasheets

[YellowJacket]

SMDFlea thank you so much, that information was very important to me! I am sorry, that I didn't check that topic before, I somehow missed it.

So update:
- first picture is SY8284CRAC, but datasheet is probably still not available, there is only some schematic of its connection on google. Anyway, I was able to measure 5V at one of its pins ( capacitor directly connected on it ), which is not connected to 5V switching supply. So, considered it as working fine
- second picture is NB679A, and it works correctly - both switching and LDO 5V voltage is up and running
- third picture is NB680, and it works - switching voltage is 3.3V and LDO voltage is 3.0V. Moreover, output from LDO regulator 3.0V is directly connected to those two capacitors nearby EC, I mentioned before. So from this point, I suppose, LDO for 3.3V is up and running and EC has its power.

[YellowJacket]

Looks like I am not alone, who is lost in this case without schematic. So to finish it somehow - do you guys at least have any idea, how to confirm dead EC ( corrupted EC firmware included ), eventually dead PCH, without schematic?
Also, is 1.4 ohm resistance to ground on that 1V power rail too low?

[mcplslg123]

Resistance to GND on 1V rail at 1.4 Ohms is considered too low indicating perhaps towards a shorted PCH. Without schematic & boardview, its impossible to troubeshoot a BGA EC.

Since, 3V LDO is present and still dc jack light is not glowing, it could be either bad main bios or corrupt ec firmware. Try flashing them both first preferably from HP official biosupdate file .

[piernov]

LDO output should be 3.3V, if it is 3.0V it is maybe pulled low by a shorted component.

[YellowJacket]

Thank you, piernov. Actually, you hit the jackpot. Amazing deduction!

I tried to hook a PSU on the LDO 3.3V output ( even, if there is kohm range ), and current consumption was around 300 mA. And no, it was no EC. There was two schottky diodes in its way, and behind second diode was like zero point something resistance to ground. Injection of 0.9V at that point heated up PCH in up-right corner of its crystal. So yeah, nice to meet you, donor board.

I only wonder, if this was just random failure, or the customer did something ( he previously wanted me only to fix the USBs - messing with USBs can fry PCH ) and he caused it all. Anyway, thank you all guys for your support and patience, I wouldn't made a single step without your clues. Take care, see you next time.

[piernov]

Yes, typical short on the RTC power rail sadly. Can happen randomly but yes something on USB can also damage the PCH.