Lenovo N500 - No power

[rtstorm]

Hi, i have this lenovo N500 that wont start. It wont spin fan.

I found that rail i marked on picture is shorted with ground (13ohm) but i cannot find where, please help.

[rtstorm]

Re: Lenovo N500 - No power

PQ18 is OK, and PQ12 does not exist

[khaahk]

Re: Lenovo N500 - No power

13 ohm is normal resistance for vga chip.

[rtstorm]

Re: Lenovo N500 - No power

ok, i found that one MOSFET have oscilating voltages.

[khaahk]

Re: Lenovo N500 - No power

With battery connected? Without?

[rtstorm]

Re: Lenovo N500 - No power

Without, i do not have battery

[dellxps15]

Re: Lenovo N500 - No power

hi, if notebook doesnt start, first look for usual 3v and 5v always if present or not. then we can go on PL10 PL11 coil. check 3 and 5 volt here

[rtstorm]

Re: Lenovo N500 - No power

i have 3V and 5V for few seconds, then it go to 0V

[rtstorm]

Re: Lenovo N500 - No power

the ovner of laptop say that it worked on battery, but no charger. Is this the PU10 fail?

[dellxps15]

Re: Lenovo N500 - No power

if with battery charged it works ill focus more on the dcin circuit rather then charger problem

[rtstorm]

Re: Lenovo N500 - No power

ok, i check PU10 and i found that VIN have oscilating voltage 8v to 14v

[rtstorm]

Re: Lenovo N500 - No power

Pq42 ok

[khaahk]

Re: Lenovo N500 - No power

If the owner is correct, then pu10 should be fine, look for the charger ic PU1 fault or circuit around it.

[rtstorm]

Re: Lenovo N500 - No power

ok i found that PQ38 have oscilating voltages on D

[rtstorm]

Re: Lenovo N500 - No power

check PQ38 IT IS ok, I TRY TO REMOVE PL12 and then on PQ38 i have stable 17V. Is this the PU1 fail?

[spleenharvester]

Re: Lenovo N500 - No power

By VIN do you mean the +ve voltage point on the DC jack itself?

If so check for continuity between the ground nearest to the oscillating voltage points and the ground on the barrel of the DC plug. A good adapter wouldn't work when loaded to 8v. You may have an open ground somewhere.

[rtstorm]

Re: Lenovo N500 - No power

i mean VIN marked on PU10

[spleenharvester]

Re: Lenovo N500 - No power

Oh yeah I see. So no oscillation at the DC jack?

[rtstorm]

Re: Lenovo N500 - No power

no, on DC jack i have 19V. In this rail i have oscilate voltages.

[spleenharvester]

Re: Lenovo N500 - No power

Firstly that CHG_B+ rail is confusing me, it doesn't seem to connect to anything else on the schematic. But that aside for now, I would try removing PQ5 and seeing if that has the same effect. I doubt the ceramic caps are shorted or else it would be dead. It looks to me like something closest to the CHG_B+ side of PL12 is causing the oscillation, not PU10 itself.