Lenovo THINKPAD T470S NM B081 REV1 DEAD

[Yosua]

hi friends, here I want to ask for your help, because currently I am working on a Lenovo Thinkpad T470s with the nm code b081 rev 1, the case is the first time it is turned on when the charging cable is inserted it can turn on but can turn off for a few minutes and when the power button is pressed it can no longer turn on as before, but when the charging cable is removed and inserted again, it can turn on again but turns off again

on the dcin path I have measured PQ1 and PQ2

when in normal conditions they appear 19v on the source and drain then the gate appears 9v

but when the condition suddenly turns off, PQ1 has 19v on the source and so does the gate appears 19v.

I hope some friends can help me, thank you

[questore]

Hi, welcome,
Measure Gate tó source resistance ön PQ1

[Yosua]

Thank you for taking the time, the result of the diode mode measurement is 1.446

[questore]

Thank you for taking the time, the result of the diode mode measurement is 1.446

Measure it in resistance mode. and post the result

[Yosua]

The result is 199k ohms when the black probe is on the gate and the red on the source and 91k ohms when the probes are swapped.

[questore]

At first when you can turn on the laptop is it showing and display?

[questore]

The result is 199k ohms when the black probe is on the gate and the red on the source and 91k ohms when the probes are swapped.

when you got 19v on gate and then remove power what resistance you got here?

[Yosua]

At first when you can turn on the laptop is it showing and display?

When the laptop is on, everything runs well and the screen can display images.

[Yosua]

when you got 19v on gate and then remove power what resistance you got here?

This is the measurement result when the laptop is off and my charger is removed, sir.

[questore]

When the laptop is on, everything runs well and the screen can display images.

Do the laptop turn off by itself after XX minutes?

[Yosua]

Do the laptop turn off by itself after XX minutes?

True, but it can't be determined how long it can turn on, sometimes it can enter windows, but when the machine feels warm, it can only reach the windows logo and then turns itself off.

then when the condition is off but the charger is still attached to the PQ1 SOURCE & GATE, 19v appears, after that I tried to unplug and reinstall the charger then all fets (PQ1 & PQ2) have normal voltage, SOURCE & DRAIN: 19V, GATE: 9V

[questore]

Could be an overheating protection. I would check the heatsink if it is contacting the cpu and GPU properly.

[mcplslg123]

All symptoms so far indicates problem in charging circuit as +19V rail suddenly cuts off. Right?

I'll bet for two things only
01.A burnt resistor on BTST pin of charging IC.
02.Missing connectivity on ACN/ACP to CLR or CSN/CSP to CLR

[Yosua]

All symptoms so far indicates problem in charging circuit as +19V rail suddenly cuts off. Right?

I'll bet for two things only
01.A burnt resistor on BTST pin of charging IC.
02.Missing connectivity on ACN/ACP to CLR or CSN/CSP to CLR

for now the development is, when my 3v&5v coils are broken, the 19v line is safe, does this mean the TPS5128 IC is damaged or weak?

[Yosua]

Could be an overheating protection. I would check the heatsink if it is contacting the cpu and GPU properly.

Thank you friend, but the processor heatsink and cooling paste are still safe

[mcplslg123]

Answer post#13 first.
We cant advise without proper feedback.