Lenovo V14 G2 heating component

[mon2]

Boardview for the NM-D521 appears to be a match to your board. Therefore we have access to the schematics as well.

[Nagyesz]

I haven't downloaded the schematic yet, as I still want to master the bv for now, but I'm increasingly seeing that knowledge of both will unfortunately be necessary very soon

So, should I start by injecting 1V into PJ6003 first, regardless of which rail? (+3VLP, +3VL)

To be honest, I've looked at the schematic, but my eyes aren't quite adjusted to it yet. What will my next will be?

[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.

[Nagyesz]

Found these

[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]

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

How should I remove the blop now?

[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]

Which would be better to remove first?

[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]

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

[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]

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]

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

[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]

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]

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]

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]

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.)

[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]

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