Lenovo T480S No signs of life

[rippsnort]

Hello,

I'm trying to bring a T480S back to life. I actually have a working sister laptop (GOOD) so that should help the troubleshooting.

T480S (BAD):
No lights when USB-C charge plugged in. No booting
Replaced battery with battery with charge, no boot

I checked the forum at tested the PU201 suggested in another thread on both laptops. The Vo VCC5MP rail is 0V on BAD.

Hopefully someone can tell me what to check next based on these mixed results.

[mon2]

Re: Lenovo T480S No signs of life

Check the voltage of VIN at PR401 (pin #2; VSYS15).

[rippsnort]

Re: Lenovo T480S No signs of life

VSYS15 measures 9.2V

I tested the JUSBC pin A4 (USBC_VBUS20_CONN) and I get 15V

[mon2]

Re: Lenovo T480S No signs of life

What is the voltage of USBC_VBUS20_CONN on the good unit ?

Same ?

[rippsnort]

Re: Lenovo T480S No signs of life

Yes, same 15V.

[mon2]

Re: Lenovo T480S No signs of life

Remove all power -> meter in resistance mode -> measure the resistance to ground of VSYS15.

Review the resistance of both, the bad and non-working logic boards to compare. Post the measurements.

[rippsnort]

Re: Lenovo T480S No signs of life

Seems to vary a lot after disconnecting power sources, but
BAD - 6Meg
GOOD - 3Meg

I did notice that on the BAD, the CMOS battery seems to be dead, i don't think this could affect power? I have disconnected it.

[rippsnort]

Re: Lenovo T480S No signs of life

Note with the battery disconnected and power supply on both I get same voltage at VSYS15 of 9.2V. It is only when the battery installed on the GOOD that I get higher voltages.