Lenovo ThinkPad X1 yoga NM-B861 not have 20v

[misha97123]

Such a problem when connecting type c, the power button flashes three times, after Q281 AON6996 dualmosfet not out 20v on L5, this voltage is low 0.432v and there is only TPS51393PRJER 3.3v on L135 VCC3M there are no other voltages. I changed Q281 charger BQ25700 also flashed ec but it didn’t help.

[mon2]

Re: Lenovo ThinkPad X1 yoga NM-B861 not have 20v

What is the voltage to ground measurements of the following?

1) REGN pin # 28 of the charger IC (U196)

2) source pins 2-3-4 of Q281

3) gate pin #1 of Q281

4) gate pin #8 of Q281 (2nd DCin mosfet)

5) ACN & ACP pins - these pins gauge the current draw from the adapter.

Post each measurement.

Often, the 2nd DCin mosfet will get damaged but you have replaced it already. Was the replacement a confirmed known good part? From a donor board?

Each current sense circuit must be operational otherwise the charger IC will believe there is too much of a load and shut off the driving mosfet(s).

[misha97123]

Re: Lenovo ThinkPad X1 yoga NM-B861 not have 20v

1 U196 REGN pin = 6.092v
2 U196 ACN pin = 20.16v ACP= 20.16v
3 Q281 source 2-3-4 = 20.16v
4 Q281 gate pin 1 = 0.457v
5 Q281 gate pin 8 = 5.923v
I replace new mosfet not from donor board.

[misha97123]

Re: Lenovo ThinkPad X1 yoga NM-B861 not have 20v

Any thoughts? resistance on gates 1 and 8 is above 130 kΩ

[Sephir0th]

Re: Lenovo ThinkPad X1 yoga NM-B861 not have 20v

This is a fancy NVDC design and the voltage at L5 may inconclusive. In fact not the first time, it drives me or someone else in circles. What do you get at VSYS18?

[misha97123]

Re: Lenovo ThinkPad X1 yoga NM-B861 not have 20v

This is a fancy NVDC design and the voltage at L5 may inconclusive. In fact not the first time, it drives me or someone else in circles. What do you get at VSYS18?

Hi Sephir0th, VSYS18=12.27v and noticed that there is a voltage VCCPCHCORE 1.012v on L1612 and the pch is getting a little warm and have VCC1R05_SUS 1.055v on L1609, VCC5M 5.02v on L132 .

[mon2]

Re: Lenovo ThinkPad X1 yoga NM-B861 not have 20v

Check the resistance of each mosfet to confirm it is not leaking. Remove all power then check the resistance across the pins.

Source & drain
Source & gate
Gate & drain

Post each measurement. Interested in the dual mosfets in one package readings.

[Sephir0th]

Re: Lenovo ThinkPad X1 yoga NM-B861 not have 20v

Hi Sephir0th, VSYS18=12.27v and noticed that there is a voltage VCCPCHCORE 1.012v on L1612 and the pch is getting a little warm and have VCC1R05_SUS 1.055v on L1609, VCC5M 5.02v on L132 .

Which is actually fine for NVDC. So there are many rails up and running which is absolutely contrary to what you shared in your intitial posting. Well, we need a overview about wat is running, what is not and whether you have healty resistance all other the board (at the coils)

[misha97123]

Re: Lenovo ThinkPad X1 yoga NM-B861 not have 20v

Which is actually fine for NVDC. So there are many rails up and running which is absolutely contrary to what you shared in your intitial posting. Well, we need a overview about wat is running, what is not and whether you have healty resistance all other the board (at the coils)

coil resistance measurements:
L5 - 7kohm
L132 vcc5m - 55kohm
L133 vcc5m_pd - 50kohm
L135 vcc3m - 4.4kohm
L1603 vcccpucore - 3.6ohm
L1604 vcccpucore - 3.6ohm
L1606 vccgfxcore - 5ohm
L1607 vccsa - 15ohm
L1608 vcccpuio - 56ohm
L1609 vcc1r05_sus - 92ohm
L1610 vcc1r2a - 230ohm
L1611 vcc1r8_sus - 3.9kohm
L1612 vccpchcore - 90ohm

[misha97123]

Re: Lenovo ThinkPad X1 yoga NM-B861 not have 20v

if you connect only the battery and press the button, all the power voltages appear that I wrote about earlier but for a few seconds and not have voltage on L5, but if you connect the battery and the power supply, then there are 16 volts on the L5 coil and the charger area and q281 warm but there is no reaction pwr button, I don’t like why it’s warm charger but mostly warm mosfets q281 q282 q196, i will try to change q196... is so redicilious if the battery is connected and the power supply has 16 volts on the l5 coil, but when only the power supply does not have this voltage ... I think the problem is somewhere in the circuit after the l5 coil.

[misha97123]

Re: Lenovo ThinkPad X1 yoga NM-B861 not have 20v

i change q196 but it didn’t help, I forgot to write that when the battery and the lab power supply are connected, the current is 2.10 amps and the charging circuit is heated

[misha97123]

Re: Lenovo ThinkPad X1 yoga NM-B861 not have 20v

what thoughts?

[Sephir0th]

Re: Lenovo ThinkPad X1 yoga NM-B861 not have 20v

Besides you neded over 3 weeks to tell the full story?

Well it is a disaster. Not only for the device but also for the people who tried to assist, so far.


But to stay on topic. Actually I don't think you're on something. Behaviour might be normal (battery starts charging when it is present). CHRG_OK pin might give us a basic idea about that and/or presence of VREG3/basic function of the embedded controller.