Lenovo Y540 17ihr-81q4

[salamiman67]

I have a short but not sure how to find the origin point without the board view, It's causing the pc not to power on or charge.
Any help would be really appreciated, as I am a noob at this, and I'm not really sure what's wrong with it.

[salamiman67]

Anyone, that helps me will be my hero, please save me.

[mon2]

Can you post a pic of your board? Have a mix of boardview files and one may match yours.

Are you sure the fault is a shorted part? Usually, the fault is in the DCin mosfets. Do you have a multimeter? Hot air soldering tools? Flux? Any silk screen markings on the board will help.

The method is to use an external adjustable power supply dialed up to 1 volt and inject onto the shorted rail. Then the part that is shorted will consume the current and heat up but do not do this yet till we take some measurements on the board.

Here is a great video on this process:

https://www.youtube.com/watch?v=wp1dPG9_N1w

[salamiman67]

I will be opening it up and taking some pictures, I will also be buying a thermal camera to try to see if anything is getting hot to hopefully give me an idea. I do have a multimeter, and a cheapo soldering iron. Thank you so much for replying to me!

[salamiman67]

I hope this is enough, please let me know if I need to take pictures of something else.

Thank you for taking the time to help me.

[SMDFlea]

Those are the sub boards.Find a similar number on the motherboard,it might be on the other side so you will have to take the board out.It could be NM-C531 ?

[salamiman67]

Yes you are correct SMDFlea it is NM-C531.

[mon2]

Ok. Review the schematic for the NM-C531. Start with the DC in power connector where you insert the power adapter barrel plug. This is the entry point to power this logic board.

Locate a white color (usually) surface mount fuse (post pics if in doubt). Need to check if this fuse is defective or not. Remove all power. It is safer to do this for now. Meter in lowest resistance scale.

Short the meter probes and this is the expected range of the fuse if it is not defective / blown. Apply the same meter probes across this surface mount (SMD) fuse. What is the resistance measurement?

Next, carefully, do apply the power adapter. Meter in DC volts (30v or higher scale). Red meter probe on this fuse (either side if the fuse is ok); black to ground (metal shield is ok). What is the voltage reading on the meter? You should have ~19 volts on the meter measurement.

Confirm these measurements.

[salamiman67]

Is it the red arrow or the black arrow or neither sorry i just couldnt find anything on the board that said pf101?

[Sephir0th]

You probably need to remove the board from the chassis. There are components soldered on the other side of the board too.

[salamiman67]

ill try and do that in an hour or 2

[salamiman67]

So I checked for continuity, and it is present, I checked resistance, and it measured the same as if my probes were touching. Lastly, for voltage on the fuse there was 20.6 volts. FairRepair you were correct it was on the back of the motherboard.

[salamiman67]

im not really sure where to go from here