Dell N5010 won't turn on - +1.05V_VTT output impedance suspect

[ngth82]

Hi Guys -

I'm looking at a Dell N5010 (Intel version). I did some research and this laptop appears to fail rather often.

I found the schematics for the laptop and i'm checking the impedances on the output capacitors for each rail. Everything appears to be okay in impedance between the rail and ground (200+ kOhm) with the exception of +1.05V_VTT. This rail reads ~1.5 to 2.0 ohm on the large 330uF output caps (PTC4901 and PTC4902).

I removed the output inductor (PL4901) to isolate if the issue is on the switching regulator side, or on the output side. With the inductor removed, the switching regulator side has an impedance around 1Mohm. The output side appears to be suspect. I continued by removing the PTC4901 and PTC4902. I was able to verify these two caps are not shorted. But the output plane still reads 1.5 to 2.0 ohm. For reference, my ohm meter registers 0.5ohm when there is a dead short between the two probes.


What's the expected/nominal impedance on the +1.05V_VTT rail to gnd on a good board?

Trying to figure out if i should continue checking the 0805 and smaller ceramic caps.


Thanks!
Thomas

[ngth82]

Re: Dell N5010 won't turn on - +1.05V_VTT output impedance suspect

Does anyone have a N5010 motherboard laying around that can help? Thank you.

[atsio]

Re: Dell N5010 won't turn on - +1.05V_VTT output impedance suspect

Remove processor and check resistance again. If same resistance on +1.05V_VTT (probably you have the UMA version), replace the PCH.

[ngth82]

Re: Dell N5010 won't turn on - +1.05V_VTT output impedance suspect

Thanks. I already removed the processor a while ago. The resistance of the rail appears to be the same.

I guess it's worth a shot at removing the PCH. I can reball if necessary.

[atsio]

Re: Dell N5010 won't turn on - +1.05V_VTT output impedance suspect

Reball will not do anything when pch is shorted.

[iqtoon]

Re: Dell N5010 won't turn on - +1.05V_VTT output impedance suspect

did u fix that problem ? i have the same issue

[Dan254]

Re: Dell N5010 won't turn on - +1.05V_VTT output impedance suspect

same issue here, please help