Lenovo Y530 shuts off after few seconds

[unimatrix93]

Hello and happy new year everyone!

I have a Lenovo Y530 (NM-B701 rev1) notebook with a frustrating problem.

It's shuts iftself off after pressing the power button. I have no POST screen, only power led and keyboard light. Same symphtomes on AC and on Battery.

Things I tried:
- General cleaning and repasting, reseating RAM modules
- Reset CMOS
- Reprogram BIOS with a programmer.
- Checking main rails with Multimeter.

Only suspicious thing I found was that the dual MOSFET on the 20V rail had 25.5V, so I replaced this two mosfets with new ones, but the 26.5V is still there.

Could it be the culprit?

[mcplslg123]

Re: Lenovo Y530 shuts off after few seconds

If the MOSFET is n channel, gate voltage should be higher. So 26v seems correct there.i think they are connected to charging circuit.

[unimatrix93]

Re: Lenovo Y530 shuts off after few seconds

If the MOSFET is n channel, gate voltage should be higher. So 26v seems correct there.i think they are connected to charging circuit.

Thanks for clrafying!

That's makes sense.

I guess I check on the other MOSFETs too, there must be a short somewhere.

[unimatrix93]

Re: Lenovo Y530 shuts off after few seconds

UPDATE

So I tested the MOSFETs and I found something fishy on the +5VALW circuit.

There are 3 MOSFET on this line named QV11, QV29 and QV12:

QV11 - LBSS139WT1G - N-Channel
QV29 - AO3402_SOT-23-3 - N-Channel
QV12 - AO3402_SOT-23-3 - N-Channel

I tested these MOSFETs by setting my MM in diode mode and I measured S (red probe) to D (black probe) then reversing the probes.

First valuer is Red on S Black on D second is reversed.
QV29: 0.010V / 0.010V
QV12: 0.273V / 0.510V
QV11: 0.518V / OL

QV29 and 12 looks faulty since shouldn't it read openloop on reversed polarity like on QV11?

I attached a photo of the parts and the circuit.


I really hope I'm on the right track finally.

[mon2]

Re: Lenovo Y530 shuts off after few seconds

Place your meter in resistance mode (2k scale is ok).

Measure and post the resistance for the following:

Source & drain
Source & gate
gate & drain

for each mosfet.

[unimatrix93]

Re: Lenovo Y530 shuts off after few seconds

Here is the values:

QV11:
S-D:0
S-G:0
G-D:0
QV12:
S-D:0.276
S-G:0
G-D:0
QV29:
S-D:0.005
S-G:0
G-D:0

[mon2]

Re: Lenovo Y530 shuts off after few seconds

Desolder QV11 off the logic board and perform the same resistance checks on the removed part while it is on the lab bench. Do not power on the logic board with the part removed.

Do you still have the 0 ohm resistance readings ?

From the posted values, I would consider to replace each of these mosfets.

Reference - see the resistance table for mosfets here:

http://electronicsbeliever.com/how-t...-is-defective/

[unimatrix93]

Re: Lenovo Y530 shuts off after few seconds

Thank you for your reply!

I will desolder QV11 tomorrow and test it off circuit and I will also order a new MOSFETS... hope they are in stock.

Will report back tomorrow with the results!

[piernov]

Re: Lenovo Y530 shuts off after few seconds

Resistance measurements don't make sense. Diode mode measurements are as expected. Components are unrelated to +5VALW circuit.

[unimatrix93]

Re: Lenovo Y530 shuts off after few seconds

UPDATE

So I desoldered QV11 and also QV29 because I measured short between source and drain with the continuity test.

Here are the values off circuit:

Resistance QV11:
S-D:0
S-G:0
G-D:0

So essentially the same as onboard.

QV29 also has the same readings, the short is still present on S - D.


Shall I proceed to order the new parts?
If yes, I wonder If I can swap AO3402 with AO3400?
I asking because only the latter is avaible at the local distributor.

I also cannot find QV11 (LBSS139WT1G) in stock...

[mon2]

Re: Lenovo Y530 shuts off after few seconds

What are the settings for your multimeter for these tests ?

Can you post a pic of the multimeter ?

[unimatrix93]

Re: Lenovo Y530 shuts off after few seconds

Sure take a look

Resistance set to 2kOhm as you recommended:


Diode mode:


Continuity mode:

[mon2]

Re: Lenovo Y530 shuts off after few seconds

Ok - that makes much more sense. The OL means 'over limit' - not 0 ohms.

OL means that it is now ok to select a higher scale till you have a proper reading. Please do this and post the values.

This also means, as noted by @Piernov, that the mosfets are most likely OK

Please post again with a higher scale on your multimeter.

[unimatrix93]

Re: Lenovo Y530 shuts off after few seconds



Sure, so I tested QV11 and I managed to get a values of these:

S-D:3.5Mohm
S-G:0
G-D:0

[mon2]

Re: Lenovo Y530 shuts off after few seconds

For the same removed QV11 mosfet,

lower the resistance scale on your meter till you can read a value.

If you indeed have 0 (zero) ohms in the lowest scale (2k ?) - then the mosfet is shorted. If you see 'OL' (over limit), then the next higher scale on the meter should be used for the measurement.

Confirm once again.

[unimatrix93]

Re: Lenovo Y530 shuts off after few seconds

Sure, I just tested it with QV11 mosfet:

From lowest (200ohm) to 2Mohms I get OL. Only on the highest setting which is 200Mohms can I get a reading which is 3.5Mohm S-D.

[mon2]

Re: Lenovo Y530 shuts off after few seconds

This mosfet is ok.

Repeat the testing with the other mosfets. You do not need to remove them off the board unless the reading is very low using the 200 ohm scale on the meter.

[unimatrix93]

Re: Lenovo Y530 shuts off after few seconds

Okay!

I will report back tomorrow with the results.

Is the short on QV29 means something?

[unimatrix93]

Re: Lenovo Y530 shuts off after few seconds

Hello, here is the results

QV29:
S-D: 1.997 (2kohm)
S-G:0L (All scale)
G-D:0L (All scale)

Diode mode:
Positive to S Negative to D: 0.042V
Negative to S Positive to D:0.036V

Continuity:
Beeeeeeep on Source to Drain.

QV12:
S-D: 1.997 (2kohm)
S-G:60 and increasing (on 200k)
G-D:60 and increasing (on 200k)

Diode mode:
Positive to S Negative to D: 0.272V
Negative to S Positive to D: 0.505V

[unimatrix93]

Re: Lenovo Y530 shuts off after few seconds

Another Update

I was checking the mosfets around the CPU and GPU and I found shorts on these devices:


All of them has:
S to D
D to Ground
S to Ground

Resistance is very low between S - D and between S to Gound and S to Drain too.

Only the mosfets that are placed horizontally have these values.