Lenovo V14 G2 heating component

[Nagyesz]

Hi all!
I have a laptop that the previous owner tried to repair. It didn't have backlight, but during the repair, accidentally short-circuited two components.

Details:
Inductors:
PL5400 OL CHG_PHASE_S CHG_CHG ▶ 0.22V
PL6001 OL 3V line
PL5701 OL 5V line
PL1004 9.5Ohm P_VDDCR_SOC_PH1_30
PL1001 5.2Ohm +VDDCR_CPU
PL1002 5.2Ohm +VDDCR_CPU
PL1003 5.2Ohm +VDDCR_CPU
PL7201 52.5Ohm +0.75VALW_P ▶ 3.9V
PL7203 85.2Ohm +1.2V_P
PL7202 OL (10KOHM) +1.8VALW_P ▶ 1.16V

I measured the voltage of each inductor when the charger was plugged in (▶) rest of them has no volts, doesn't power on.

Two component which was short ciruited is FV1 CV5 B+ +LEDVDD B+ GND

Heating component is:PU6001 ! ( SY8386BRHC_QFN16_2P5X2P5 )
1 pin 1.27
2 pin 20.7V should be about 3v
3 pin 20.7v should be about 3v
4 pin 0v
13,9,5 pin 0v

Issue is most likely on the 3V line, but I simply can't find the source anywhere. How should I start?


Also
PJ6001 1V and GND
PC6015 1V and GND


Thank you in advance for the suggestions!

Also I attach boardview

[SMDFlea]

Please post a link to the boardview https://www.badcaps.net/forum/troubl...f-this-section

[Nagyesz]

Link to boardview https://www.badcaps.net/forum/troubl...-2-0-boardview

[mcplslg123]

PU6001, pin 2-3-4 are ties together and should be 19V as its VIN. Read diagram /datasheet carefully before proceeding.. What's the resistance to GND on FV1,pin1/pin2?

[Nagyesz]

Both pins are approximately 5 MΩ to GND, 20.3V travelling through


(I fixed the short circuit a while ago, replaced the capacitor, and cleaned everything with alcohol.)

[mon2]

2 pin 20.7V should be about 3v
3 pin 20.7v should be about 3v

?? Normal rail voltage is ~3v but you have 20V?

[Nagyesz]

Yes, when I measured it, that's the value I got, and this ic gets very hot. The boardview shows 3V for the ic, but due to the previously mentioned VIN, I thought it was normal, right?

[mon2]

No, no. This is Vin. This is a high voltage Vin regulator that is capable of accepting such a high voltage and lower it down to whatever. A buck regulator.

If the part is heating up, remove all power -> measure the resistance to ground of the output rails. If there is a low resistance to ground, then something is shorted on the rail and causing an excessive load and heating up this part.

See attached.

Measure the resistance to ground of pins 15 / 16 (they are tied together so either is ok). What is the measurement?

[Nagyesz]

Pin 15-16 is the lowest measured in 200kohm, both of them 6.7kohm,
14, 6 pin 0.03ohm rest of them OL and pin 10 is about 100kohm

[mon2]

Not shorted. If this part is heating up, replace it.

[Nagyesz]

Alright, I'll order it. By the way, I'm almost certain the short circuit was on the +B line, so it probably took out this IC. Thank you!

[mon2]

Forgot to ask about pin 13 = 3v LDO rail. The pins 15/16 are switching rails. What is the resistance to ground of pin # 13?

[Nagyesz]

I missed it... 13 pins is 4.6 Ohms.

[mon2]

Ouch. Remove the cap that should be on this line and then measure the resistance to ground again. Everytime, without power of course to the board. Perhaps this local cap is shorted.

[Nagyesz]

Which would be better to remove first?

[mon2]

PC6006. The other appears to be PCB trace / solder blob short / jumper. Concern if this rail is powering the EC controller which will be the device that controls your keyboard and other low level functions. Confirm if the PJ6003 is a solder blob. If yes, after removing PC6006, then can review the balance of the loads on this power rail. This LDO is a low current rail so only a few components can be powered by this internal regulator. Someone is shorted here and most likely causing the heat up of the regulator.

Excellent - first remove the capacitor. Then test again if the resistance is higher. Only if required, remove the solder blob @ PJ6003. Then we will know which area of this rail is shorting.

[Nagyesz]

Removed PC6006, solder blob is 4.6 ohms to gnd again :/

How should I remove the blop now?

[mon2]

Yes. Then check the resistance again on each side of the empty solder pads. Suspecting the short is further on the downstream / consumer side of this rail.

Use the BV file to assist. When you select this solder blob pad, who lights up on the BV file. Each is a suspect. Will do the same in a few.

[Nagyesz]

Found these

[mon2]

Ok - may have found a gold mine. Maybe. Downloaded the above linked BV file and unable to load it with my viewers. Checked my (paid) database service and they do not offer the same BV file but found the BV & schematics for the NM-D521 board. This board appear to be very similar.

Do you have access to the NM-D521 schematics? This rail does travel all over the board but there are jumper solder blobs again to disconnect the EC power rail which is from this LDO. An alternate approach is to inject 1 volt onto this rail and check who heats up.

** DISCONNECT any IO cables; WIFI Card; Ethernet card and test again the resistance to ground. Each is powered from this low current rail.