lenovo yoga 13 2191 no turning on

[questore]

Hi guys.
Laptop is not reacting to power button at all, no lights, no blinks no beeps or anything. Removed every component and the battery too.
DCIN 20v is present until the first mosfet, but not at its gate.

(SUSPECTING the BQ735 charger chip bacuse it worked from battery while it had some power.)
So made some voltage readings on BQ735 below:
1 ACN - 0.906 v
2 ACP - 0.906 v
3 CMSRC - 0v
4 ACDRV - 0v
5 ACOK- 0v
6 ACDET - 2,75 v
7 IOUT - 0v
8 SDA- 0v
9 SCL - 0v
10 ILIM - 0v
11 BATDRV - 2,12 v
12 SRN - 1,07 v
13 SRP - 1,07 v
14 - GND
15 LODRV - 0
16 REGN - 6,08 v
17 BSTR - 5,9 v
18 HIDRV - 1,07 v
19 PHASE - 1,07 v
20 VCC - 20 v

[mcplslg123]

Re: lenovo yoga 13 2191 no turning on

Yes, Replace the charger IC.

[Sametbey]

Re: lenovo yoga 13 2191 no turning on

Since it works with a battery, there is no short circuit in the + B19V line. Are your entrance mosfets intact? There are voltage values in the diagram, check it. your charging chip may be defective.

[questore]

Re: lenovo yoga 13 2191 no turning on

Replaced BQ735 but no change. Every value is the same.

[mon2]

Re: lenovo yoga 13 2191 no turning on

Is the +3v3 rail working on this logic board?

It is required for the pull-ups on the i2c lines; ilim and other pins.

Ilim is built from.a resistor based voltage divider and cannot be 0 volts (unless the pull up resistor or +3v3 are missing).

Please confirm.

[questore]

Re: lenovo yoga 13 2191 no turning on

Reworked the new bq chip since one of the soldering was loose and not connected:

Had a fanspin for 5 sec when connected the charger but now its nothing.
Laptop still does not turn on when pressing the power button.
New values of BQ735:

1 ACN - 20v
2 ACP - 20v
3 CMSRC - 19,5v
4 ACDRV - 25,1v
5 ACOK- 0v
6 ACDET - 2,75 v
7 IOUT - 0v
8 SDA - 0v
9 SCL - 0v
10 ILIM - 0v
11 BATDRV - 2,75v
12 SRN - 2,73v
13 SRP - 2,73v
14 - GND
15 LODRV - 0v
16 REGN - 6,08 v
17 BSTR - 5,9 v
18 HIDRV - 2,73v
19 PHASE - 2,74v
20 VCC - 18,3v ans sometimes goes down to 16v

[SMDFlea]

Re: lenovo yoga 13 2191 no turning on

whats the motherboard part number, is there a schematic

[questore]

Re: lenovo yoga 13 2191 no turning on

whats the motherboard part number, is there a schematic

I have no schematic

MB numbers:
38200164
9002035
Yoga 13 MB panasonic

[questore]

Re: lenovo yoga 13 2191 no turning on

Is the +3v3 rail working on this logic board?

It is required for the pull-ups on the i2c lines; ilim and other pins.

Ilim is built from.a resistor based voltage divider and cannot be 0 volts (unless the pull up resistor or +3v3 are missing).

Please confirm.

Pull up resistors are present and not blown.
I have not found 3.3v or 5v anywhere but i have no schematic

Also 20 VCC - 18,3v and sometimes goes down to 16v and it is abnormal

[mon2]

Re: lenovo yoga 13 2191 no turning on

https://www.elvikom.pl/lenovo-yoga-1...ad-t53251.html

Monitor my post from a few minutes ago:

https://e2e.ti.com/support/power-man...is-the-bq24735

So this is interesting:

(from)
https://e2e.ti.com/support/power-man.../956290/bq735f

see markings information - attached.

Respectively, full datasheets for the BQ24735 are posted on the TI website.

[mon2]

Re: lenovo yoga 13 2191 no turning on

If the 20V DCIN is dropping down then some excessive load is causing the event.

Remove the front side mosfets, starting with the one closest to the DCIN connector and continue to check if the DCIN voltage drops down or remains stable.

Power down and check for any shorted caps - check the resistance to ground on this main rail and also at every coil to ground. Any super low resistance values (ohms) ?

[questore]

Re: lenovo yoga 13 2191 no turning on

If the 20V DCIN is dropping down then some excessive load is causing the event.

Remove the front side mosfets, starting with the one closest to the DCIN connector and continue to check if the DCIN voltage drops down or remains stable.

Power down and check for any shorted caps - check the resistance to ground on this main rail and also at every coil to ground. Any super low resistance values (ohms) ?

DCIN mostfets are both 20v on source and drain too so they are fine.

[questore]

Re: lenovo yoga 13 2191 no turning on

DCIN mostfets are both 20v on source and drain too so they are fine.

Of course only when i plug in the battery then I got voltages on drain.

BQ735 pin #20 VCC resistance is sometimes 0 Ohm sometimes not . I can try to remove the resistor and the capacitor right on that line to see if 0 ohm remains

[mon2]

Re: lenovo yoga 13 2191 no turning on

BQ735 are the markings of the BQ24735 charger IC.

Please see attached.

[questore]

Re: lenovo yoga 13 2191 no turning on

A Voltage Regulator IC numbered 8150L (QFN 16) got shorted.
Found with an infrared camera.
I ordered a replacement (30 days shipping at best) Be back with result after replaced the IC.

[questore]

Re: lenovo yoga 13 2191 no turning on

Realized there is more problem with the board.

After removed the 8150L IC, the short to ground around it has gone BUT...
The BQ735 charger chip still has low VCC.

I have a 2Ohm short on 3.3v I think,because:
SDA, SLC, ACOK, and ILIM pin goes to 3.3v with a resistor and all further end of those resistors are 2 Ohm to ground.
I'm i correct?
Whats next?

[DanielDacko]

Re: lenovo yoga 13 2191 no turning on

Realized there is more problem with the board.

After removed the 8150L IC, the short to ground around it has gone BUT...
The BQ735 charger chip still has low VCC.

I have a 2Ohm short on 3.3v I think,because:
SDA, SLC, ACOK, and ILIM pin goes to 3.3v with a resistor and all further end of those resistors are 2 Ohm to ground.
I'm i correct?
Whats next?

Inject 1V unlimited A and see what heats up.

[questore]

Re: lenovo yoga 13 2191 no turning on

Inject 1V unlimited A and see what heats up.

I have ordered parts for lab power supply and see whats happens after injecting 1v

[questore]

Re: lenovo yoga 13 2191 no turning on

In the meantime i have measured the resistor value in VCC line right next to bq735 and it is 37kOhm so I think it needs to be replaced. Since I don't know what was the original value I will replace it with the most common 10 Ohm resistor.

[mon2]

Re: lenovo yoga 13 2191 no turning on

37k on Vcc is too high. Yes 10 ohm sounds correct. Also inspect the dual diode on your logic board if present that feeds this rail.