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Old 11-13-2019, 06:08 AM   #1
GIFixed
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Default Yoga 700 14-ISK

Yoga 700 14-ISK

Dear all,

Our customer came in with a lonovo yoga 14-ISK, that "suddenly died".

No history.
No water damage.

It seems the RAM socket was changed: flux residue and not 100% perfectly aligned.

On some power jumper there are 9V generated from AC-IN:

PJ201 9V
PJ204 9V
PJ802 9V
PJ803 9V
PJ301 9V
PJ801 9V (AT BACKSIDE)

PJ103: -0.94V (AT BACKSIDE)
PJ302: 0V
PJ101: 19.3V
PJ102: 7.3V -> PF101 (X MARK, OK) -> B+ TERMINAL
PJ304: 0V

PJ202: 0V
PJ205: 0V
PJ402: 0V
PJ401:
Could not find schematic for this board.

ICs on the board:
lenovo IT8396VG (BGA)
PU101: BQ24770
PU701: NCP81208

ICs with smd markings:

PU201: AWV5KC
PU202: AWW5LB
PU203: AWS5NA
PU301: AKUF 926
U35: R23N
U101: 5AF2F
U56: WE 5bG

Power button missing 3V!

Any help, thanks
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Old 11-13-2019, 08:14 AM   #2
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Default Re: Yoga 700 14-ISK

PU201-AWV is your 3V ic and PU202-AWW is your 5V ic. Check whether any of them is shorted. Post clear photo of mb as schematic is unavailable. Btw, what is the mb code??
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Old 11-13-2019, 12:39 PM   #3
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Default Re: Yoga 700 14-ISK

Quote:
Originally Posted by mcplslg123 View Post
PU201-AWV is your 3V ic and PU202-AWW is your 5V ic. Check whether any of them is shorted. Post clear photo of mb as schematic is unavailable. Btw, what is the mb code??
Thank you for your reply.

I would post photos, but I should recharge the camera first.

Sorry, I missed the MB code:
BYG43 NM-A601

After posting my question, I came across a russian forum mentioning the AWV5KC and AWW5LB from a different laptop. One member answered these two should be:
SY8286B (3V) and SY8286С (5V).

I could not find data sheet for SY8286B nor SY8286C, but for SY8286A

Using that data sheet, I found following for SY8286A:
http://www.szyucan.com/upfile/IC-PDF/SY8286A.pdf

Measured for PU202-AWW (5V):
IN: 9V
EN: 9V
VCC: 0V
BYP: 5V! (where does this 5V come from?)
LX (coil): 0V (output)!

Measured for PU201-AWV (3V):
IN: 9V
EN: 9V
VCC: 0V
BYP: 0V
LX (coil): 0V (output)!

All DC-DC converters have 9v as input, but no output.
Only DC-DC converter that seems (maybe) working is the BQ24770 which produces 7.4V from the 19V AC adapter.

The 5V rail is 10 ohm to ground.

I tried to remove PJ202 (5V) jumper and inject 5V. The U101 (5AF2F) gets hot.

What is the purpose of the U101? Maybe switching betwen 5V USB and 19V USB AC adapter?

Attached pictures of the motherboard taken with my iPhone.

Could it be that the EC is always reset?
Attached Images
File Type: jpg fullsizeoutput_686.jpg (339.3 KB, 9 views)
File Type: jpg fullsizeoutput_689.jpg (251.8 KB, 5 views)

Last edited by GIFixed; 11-13-2019 at 12:42 PM..
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Old 11-13-2019, 10:58 PM   #4
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Default Re: Yoga 700 14-ISK

BQ24770 diagram
http://www.ti.com/lit/ds/symlink/bq24773.pdf

Charger IC in your board is bit different from the earlier days as it has Pmon pins. This drives the B+ rail. I doubt something is wrong here as your rail is 9V. So you need to probe this IC first. Since schematic is not available, i may be wrong and hopefully other members will correct me if i'm wrong.

Last edited by mcplslg123; 11-13-2019 at 11:02 PM..
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Old 11-14-2019, 10:47 AM   #5
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Default Re: Yoga 700 14-ISK

So, I worked more on this motherboard today. Here what I found:

The PU201 generates 3.3V internally. This 3.3V is connected to the +3VALW_EC thru the zero ohm resistor shown on attached photo. From the other side of the resistor connected to EC and reset circuit for the EC: diode, resistor and capacitor.

This 3.3V was shorted to ground by the EC. When I removed the 0 ohm resistor, it was back on. But the 3V output of the PU201 was not available.

If I inject 3V after the resistor, the EC gets hot where I marked with red circle on the EC (IT8396GV).

Do you agree with me, that the EC is shorted? maybe dead?
The problem is this EC is BGA, så we have to get it out to check the short.

Anybody have the pinout and maybe schematic for this EC?

Any suggestions? Thanks.
Attached Images
File Type: jpg yoga700_NM-A061_3VALW_EC.jpg (241.5 KB, 12 views)
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Old 11-18-2019, 09:40 AM   #6
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Default Re: Yoga 700 14-ISK

Reflowed the EC (IT8396VG). Still shorted, mabye 5 ohm to ground.

Any other boards using this EC?
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Old 11-18-2019, 03:33 PM   #7
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Default Re: Yoga 700 14-ISK

Quote:
Originally Posted by GIFixed View Post
Reflowed the EC (IT8396VG). Still shorted, mabye 5 ohm to ground.

Any other boards using this EC?
Have you tried resoldering it? Kinda odd that it heats up in the corner. Dont know how large the die is but i belive it won't extend to the edges of that package.
Maybe someone messed up reballing it? Shorted balls maybe?
Can't find anything about IT8396VG on google. You sure it is correct?
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Old 11-18-2019, 10:54 PM   #8
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Default Re: Yoga 700 14-ISK

Quote:
Originally Posted by KvnTM View Post
Have you tried resoldering it? Kinda odd that it heats up in the corner. Dont know how large the die is but i belive it won't extend to the edges of that package.
Maybe someone messed up reballing it? Shorted balls maybe?
Can't find anything about IT8396VG on google. You sure it is correct?
Google shows this ic. just type IT8396VG-192
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Old 11-19-2019, 03:42 AM   #9
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Default Re: Yoga 700 14-ISK

I will try removing the EC IC and check underneath.

Attached photo of the EC getting worm in a specific area about the "v" in Lonovo word on it.

The other photo showing type number.


Could not find datasheet for it. And buying over eBay/Aliexpress takes too long time to arrive.

Anybody knows if I can buy this chip in Germany or in Europe?
Attached Images
File Type: jpg IMG-3596.jpg (949.2 KB, 4 views)
File Type: jpg 3F436725-FA1F-467E-9B51-12E836C0EEF1-4044-00000367A7E51118.jpg (537.0 KB, 5 views)

Last edited by GIFixed; 11-19-2019 at 03:44 AM..
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Old 11-19-2019, 05:32 AM   #10
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Default Re: Yoga 700 14-ISK

Removed the EC and the 4 ohm short is gone.

The EC in photo is flipped on its back vertically (up-down). Left-right is correct.
Attached Images
File Type: jpg IMG-3600.jpg (698.8 KB, 8 views)
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Old 11-19-2019, 06:30 AM   #11
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Default Re: Yoga 700 14-ISK

Going by your pic of lifted ec, it doesnt seems reballed. So the ec is actually shorted. As you are aware, needs to be replaced.
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Old 11-19-2019, 06:47 AM   #12
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Default Re: Yoga 700 14-ISK

Yup. It's dead.
You can either buy the chip from china or get a donor board. There are two from Germany on eBay for 25€ and 30€. Not sure if they have the same fault though.

You are better off buying that chip from aliexpress I guess.
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Old 11-19-2019, 06:52 AM   #13
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Default Re: Yoga 700 14-ISK

On pic, red arrow indicates pin shorted to ground.

Green line indicates these three pins are on board connected together to the +3VLP (100 mA) LDO output line from PU201.

When one of these pins is shorted on the EC itself, the +3VLP is shorted to ground.

Click on picture to see it clearly.
Attached Images
File Type: jpg IMG-3600_2.jpg (1.28 MB, 9 views)

Last edited by GIFixed; 11-19-2019 at 06:54 AM..
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Old 11-19-2019, 06:57 AM   #14
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Default Re: Yoga 700 14-ISK

You could inject 3.3v directly into the chip and see if it heats up. Just solder really small wires to it. Finding a gnd pad won't be hard.
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Old 11-21-2019, 01:41 PM   #15
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Default Re: Yoga 700 14-ISK

Quote:
Originally Posted by KvnTM View Post
You could inject 3.3v directly into the chip and see if it heats up. Just solder really small wires to it. Finding a gnd pad won't be hard.
I didn't have the time to try your suggestion.

By the way, we have bought a new IT8396VG from AliExpress. Will arrive in 3 weeks.

I will post a result when the new one is tested.
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