HP 15-db0070ns laptop (LA-G078P) : does not power on, had liquid inside

[dicky96]

Hi guys
I have this HP laptop for repair. The owner says that their cat knocked a vase over, and water had been dripping into the laptop for a few days.

They then left on one side for several months. Either the owner or the technician who brought it to me tried to power it up but it does not start

I did not try to power it up, though I did check the charger is OK

There is some corrosion on the HDD around the spindle/motor area

There was also some corrosion on and around the KB9022Q D SIO

I cleaned all this up with ISO. There is a MLCC capacitor very near the SIO that looks like either the input or output capacitor to a buck regulator near the SIO. This was badly corroded and one end cap was missing so I replaced it with a new 10uF MLCC, not knowing the correct value

Once I fixed those problems i tried to power it up, it seems totally dead.

I have 19V getting through the first two MOSFETs after the DC in socket. The third MOSFET has 19V going in and 3V coming out. There is a buck inductor on the other side of the PCB under this MOSFET and that also has 3.0V so it is probably a standby supply. I can't see any CMOS battery on the motherboard so that kinda makes sense

There is no voltage on any other inductor. The battery only appears to have 2.95V on two of the pins and nothing on any of the others.

I can't find a datasheet for the KB9022Q SIO. I did a resistance check and the 3.0V 'standby?' supply does not directly connect to any pins on the SIO.

I then had a look around the SIO for any sort of power supply and I only find 0.5V on one pin, nothing else (other than a few pins reading 0.1V-0.2V)

I'm kinda assuming the SIO needs a 'permanently on' supply of some sort before it can power up anything else on the motherboard.

I tried to check for 3V on the power on switch but it looks like the contacts are not accessible to test that.

Does anyone have any further ideas, info or even better a schematic for this laptop?

Thanks
Rich

[mcplslg123]

Re: HP 15-db0070ns laptop (LA-G078P) : does not power on, had liquid inside

There is a jumper PJ303 near PU301 which is your 3v Regulator. PJ303 is the 3.3V LDO which powers the kbc. So first check whether you have 3.3V on PJ303. If yes,remove kbc and check voltage on vcc pin pad of kbc again . If the voltage appears on kbc vcc pin after removal of kbc-then you need to replace the kbc. However, if you dont have 3.3V on PJ303, then remove the jumper and check whether you have 3.3V on PU301 side of jumper. Do measure resistance on jumper PJ303 before doing anything.

[SMDFlea]

Re: HP 15-db0070ns laptop (LA-G078P) : does not power on, had liquid inside

Can you tell me what marking is on PQB1 please ,to help another member with the same motherboard - https://www.badcaps.net/forum/showthread.php?p=1082614

[sanaa]

thx good