Thinkpad E490 - dead, +1.8VALW shorted

[juergenb]

Hi,

i have a E490 with NM-B911 (ThinkPad E490 14" Intel i5-8265u).

Notebook doesn´t start, Shift LED and Power LED is lit.
SSD, HDD, Memory is fine (tested these external).

PU801 gets extrem hot.

Other compents getting warm (CPU i5, SSD, Memory Module)

So i removed PJ802 Bridge.

These Voltages of PU801 (RT9059GQW)

+1.8VALW
+3.0VALW
+5.0VALW

are fine and it stays cold.

If i inject +1V/5A at PJ802 nothing get´s hot on the board.
PSU Drops to 0.4V and current is limited about 2.4 Amps.

Customer told me that the kids used the notebook in bed before failure.

I assume that the CPU/PCH is dead?

I have the Schematics and a Boardview (JPG).

Can someone confirm?

Thanks in advanced.

[natic]

Re: Thinkpad E490 - dead, +1.8VALW shorted

If i inject +1V/5A at PJ802 nothing get´s hot on the board.
PSU Drops to 0.4V and current is limited about 2.4 Amps.

Hello!
Repeat the test and rise up the current limit on your power supply.

I assume that the CPU/PCH is dead?

Yes, unfortunately the PCH part (small core) of the APU hybrid is unfortunately very likely damaged. However repeat the test as suggested first fir confirmation that.

[Sephir0th]

Re: Thinkpad E490 - dead, +1.8VALW shorted

Something is wrong with the PSU setup, though. If you inject 1V/5A, the load either draws the full 5Amps with voltage drop present or it reaches 1Volts without drawing the full 5 Amps. Both at the same time is impossible.

[juergenb]

Re: Thinkpad E490 - dead, +1.8VALW shorted

Hi,
i have a Siglent 1305X with 30V @ 5Amps max, i had the Voltage Limit at 1V and Current Limit is at 5A.
At the time i purchased this i wasn´t clear if i would need 30V/5A (so i would have 19V available) or i need the 16V/8A Modell...
Maybe i need a short killer

I soldered a cable to PJ802 and connected at several GND locations.

PSU showed Output @ 0.4V and at 2.4A (I controlled this with a Fluke too).

The Voltage was no more than 0.4V - 0.5V on the output so i raised the voltage up to 1.8V (+1.8VALW) but the current was still at 2.4A - 2.5A.

Maybe the PSU is not good for such diagnose and can´t deliver 5 Amps.

I checked the Schematics and +1.8VALW has some connections to Resistors, but most of them > 1kOhm, so they can´t be bad.

+1.8VALW connects to

+VDD18 <50> Audio
+1.8VS_VGA <30,32,34,38> GPU
+1.8VALW_PCH <19> PCH
+VCCPRIM_1P8_1P <19>

Only with the Lenovo USB-C Powersupply i get enough current through PU801.

But i got a burnmark from PU801 at my fingertip.
And PCH, SSD and RAM Module is warm.

I checked

R1909
C1918
R5002
C1907
C1908
R1912
C1918

but they seem to be cold.

[juergenb]

Re: Thinkpad E490 - dead, +1.8VALW shorted

"Something is wrong with the PSU setup, though. If you inject 1V/5A, the load either draws the full 5Amps with voltage drop present or it reaches 1Volts without drawing the full 5 Amps. Both at the same time is impossible."

The DUT draws 2.4A, it looks like the current is limit somehow.
For a Voltage of .4V the resistance must be arround 0.17 Ohms.

Maybe my cable to the DUT is to weak.

[natic]

Re: Thinkpad E490 - dead, +1.8VALW shorted

The DUT draws 2.4A, it looks like the current is limit somehow.
For a Voltage of .4V the resistance must be arround 0.17 Ohms.

True.

Set your laboratory power supply to 1V and current limit for example to 3.5A. Then bridge (short) the end of test wires together and read the voltage and current from the display on your power supply.