1 Legion Y540-15IRH, Shorted can't seem to find the source of theProblem
I am still a beginner and I have a lot of gaps in my knowledge, but I will try to explain the situation the best I can.
The laptop is Lenovo Legion Y540-15IRH, and the motherboard model is NM-C221 Rev 2.0, Schematics NM C221 (Pass Y540) (Password: Y540) and BoardView can be easily found. To save time I started with the exact problem in my laptop as the one shown in this video:
https://www.youtube.com/watch?v=tfucZ_WK...
I was checking the voltages I found that the main power rail V20B+ is good, and same for the +3VALW circut, but when I tried the +5VALW, the circuit was shorted and I think the problem came from one of these 2 MOSFETS PQ603 (AON7380_DFN8-5) and PQ604 (AON6380_DFN8-5), and while checking voltage with the multimeter on DC mode I made a mistake of touching two pins of the drain of PQ603 with the red probe, which caused more problems. And now I think there is a short even in the main power rail, since when checking for voltages I could see that there is voltage coming in to PQ201(one of the two DCin mosfets) 20.5V, but no voltage coming out from that MOSFET or anything else afterward. So then I did more measurements:
Voltage of both Source and Gate of PQ201 to ground = 0V
For PQ201 resistance Between:
Source (Red Probe) & Drain (Black Probe)= 2.02
Source (Red Probe) & Gate (Black Probe) = 3.62
Gate (Black Probe) & Drain (Red Probe) = 5.41
For PQ202 resistance Between:
Source (Red Probe) & Drain (Black Probe)= 2.06
Source (Red Probe) & Gate (Black Probe) = 3.63
Gate (Black Probe) & Drain (Red Probe) = 5.33
First CLR (Current Load Resistor) after the 2 DC-IN mosfets is PR201, and it resistance to Ground = 0.01
So maybe the problem is in the CPU, so I measured the Resistance to Ground of the group of inductors close to it, on the lowest scale:
PL3001,PL3002, PL 3003 & PL3004= 1.3
PL3021= 10.5
PL901 = 32.4
My questions are:
-Do I have a shorted CPU?
-Or do I have a different problem? If so, can anyone suggest what would I need to do next to find this short? and revert the motherboard to it initial problem and then fix from there.
I would really appreciate any help, thanks in advance. And if you need clarification or have any questions, I would be happy to do so.
crwdns2934109:0crwdne2934109:0
Hi @hybridfirst,
Any voltage on PR206 or VIN on PR209?
For PQ201 to turn on I think that you would need a voltage coming out from the PU201 IC on the ACDRV lead
crwdns2934271:0crwdnd2934271:0 jayeff crwdne2934271:0
@jayeff Hi, thanks for the help, here is the result:
PR209 = 20.3V on both sides
PR206 = between 0.05-0.12V (keeps changing) on the ACDRV lead
What do you suggest?
crwdns2934271:0crwdnd2934271:0 Hybrid First crwdne2934271:0
@hybridfirst
Looking at the datasheet for PQ201 there isn't enough voltage being supplied to the gate to trigger it on so I'm wondering why not.
The correct voltage is being applied to PU201 but for some reason it's not turning on PQ201 etc.
At this stage all you're looking for is that when the charger is connected that the laptop indicates that the battery is being charged and this doesn't need the CPU.
To me at this stage everything is controlled by PU201 so perhaps check that there's battery voltage at PL201.
Once you get voltage at V20B+ you're going to get the necessary other voltages (barring more problems further on i.e. no +5VALW), being derived from it, but since PQ201 & PQ202 aren't being turned on that's not happening.
Something is preventing PU201 from functioning correctly.
At least this is what I'm thinking but that doesn't mean I'm right ;-)
crwdns2934271:0crwdnd2934271:0 jayeff crwdne2934271:0
@jayeff Actually that makes sense, I checked the voltage to ground for PL201 and it's 0.13V, so what does this mean?
maybe I should replace PU201?
crwdns2934271:0crwdnd2934271:0 Hybrid First crwdne2934271:0
@hybridfirst did you replace PQ603 since that most likely got shorted out as well.
crwdns2934271:0crwdnd2934271:0 oldturkey03 crwdne2934271:0
crwdns2934275:08crwdne2934275:0