Lenovo Z500 LA-9063P VIWZ1_Z2 Rev. 1.0 no power

[Conste]

Hello together,

I have a mainboard from a lenovo Z500 here which doesn't have power.
Seller claims water damge, but I don't see any water damage.

After the first MOSFET 20V are there, but after second I only have 0,9V in AC mode.

When I attach battery to the unit I have 3V and 5V on coils, but not on bios chip. After second Mosfet also voltage.

Coils are not shorted, I checked for obvious things like shorted caps I think.

Schematic is available:

https://www.alisaler.com/lenovo-z500...1-0-schematic/

Could somebody please advice me what to do next?

Thanks in advance.

[Adenitz]

Re: Lenovo Z500 LA-9063P VIWZ1_Z2 Rev. 1.0 no power

The very first thing is to check whether two input MOSFETS are OK. In this case PQ301 and 302. Remove all power and measure resistance G-S, G-D and D-S on both MOSFETS.
No matter if there is 19V after first MOSFET (there is a body diode). You need to check whether it is shorted.
Also, after second MOSFET, on PR302 measure resistance to ground (with all power removed from the board). These are two steps to begin with.

[Conste]

Re: Lenovo Z500 LA-9063P VIWZ1_Z2 Rev. 1.0 no power

Okay thanks, first one (4407A) P-Channel was defective, was not switching.

Second one (4423L) also P Channel was okay.

I desoldered both components to test them according to this site:

https://www.homemade-circuits.com/ho...using-digital/

Resistance is about 5-6 Mohms climbing and falling.

Edit: Unit is charging battery and turning on now, no screen until now, but I am on it.

Edit2: Unit is posting fine! It seems like the old Sorin trick with bridging the mosfet is not working all the time.

[Adenitz]

Re: Lenovo Z500 LA-9063P VIWZ1_Z2 Rev. 1.0 no power

Edit2: Unit is posting fine! It seems like the old Sorin trick with bridging the mosfet is not working all the time.

Old Sorin's trick works most of the time in sense that a dead laptop can turn ON. However almost always there is some other problem to be noticed, such as unable to charge battery for example.

Can you please tell us what exactly did you do in order to make the laptop work again?

[Conste]

Re: Lenovo Z500 LA-9063P VIWZ1_Z2 Rev. 1.0 no power

After measuring the MOSFETs I searched for working 4407A from a scrap board. Then I soldered both MOSFETs on the board again.

When putting power on the board I saw 19v on shunt resistor (PR302) and checked other voltages (3v3 and 5v on coils).
Then I connected the battery and saw that charging lieght came on.

Finally I completed the board with RAM/CPU etc., but had no screen. Then I flashed a EC and BIOS dump from here and got it working.

So it was really the first MOSFET, still cannot believe it

[Adenitz]

Re: Lenovo Z500 LA-9063P VIWZ1_Z2 Rev. 1.0 no power

I repair laptops as a hobby, mostly for family and friends.
Usually, when laptop has no power the following reasons are most likely:
- shorted input MOSFETs
- shorted ceramic cap somewhere on the board (usually one can measure low resistance to ground at current sense resistor)
- charging chip got hit because something got shorted before (MOSFET or cap)

If everything from above is OK, then the probability of repair is very very low.

[Conste]

Re: Lenovo Z500 LA-9063P VIWZ1_Z2 Rev. 1.0 no power

I repair laptops as a hobby, mostly for family and friends.
Usually, when laptop has no power the following reasons are most likely:
- shorted input MOSFETs
- shorted ceramic cap somewhere on the board (usually one can measure low resistance to ground at current sense resistor)
- charging chip got hit because something got shorted before (MOSFET or cap)

If everything from above is OK, then the probability of repair is very very low.

I do it as a hobby also and try to become better and better.

Another reason can be a damaged bios, which is really easy to fix.
I have also changed a KBC from Asus A555L before which worked afterwards perfect, but this was a hard job. Thanksfully we have a good microscope at work

[Adenitz]

Re: Lenovo Z500 LA-9063P VIWZ1_Z2 Rev. 1.0 no power

Conste, in my experience, BIOS faults are also rather frequent, but in all cases there is power and fan usually works, but no picture. If there is NO power at all, then usually caps or Mosfets are to blame.