Lenovo ideapad 5 - identify shorted chip

[s_henya]

Hi guys,

Got this nice laptop in yesterday.
MB: GS557GS558

Previous owner dropped a screw that shorted the MB.
Removed faulty cap that got burned due to short.
Found burning hot ic
QqBUA- no information about it in google.
Any advice what is this IC?

Would be a shame to scrap this board…

[mon2]

Re: Lenovo ideapad 5 - identify shorted chip

Silergy

Qq*** SY8386BRHC - N/D (EL432 EL532 LA-H131P)

[s_henya]

Re: Lenovo ideapad 5 - identify shorted chip

Silergy

Thanks!

All of these ics are compatible replacements?

[mon2]

Re: Lenovo ideapad 5 - identify shorted chip

The tail end of the above are the logic boards that use this part so you can study the schematic.

As long as the part starts with Qq, you will be ok. The rest are usually datecode markings.

Here is one vendor:

US $7.71 18%OFF | (5piece)100% New SY8386BRHC SY8386B QqAZB QqBTB Q9A.. QFN-16 Chipset
https://a.aliexpress.com/_mqsEFbS

[s_henya]

Re: Lenovo ideapad 5 - identify shorted chip

The tail end of the above are the logic boards that use this part so you can study the schematic.

As long as the part starts with Qq, you will be ok. The rest are usually datecode markings.

Here is one vendor:

US $7.71 18%OFF | (5piece)100% New SY8386BRHC SY8386B QqAZB QqBTB Q9A.. QFN-16 Chipset
https://a.aliexpress.com/_mqsEFbS

Thank you so much!
Will update after replacing it.

[s_henya]

Re: Lenovo ideapad 5 - identify shorted chip

Update:
So i finally got the replacement IC from china.

Unfortunately i have the same symptom- overheating ic

i collected measurements
Pin1: 0.43v
Pin 2,3,4: 12.25v
Pin5: 0.015v
Pin6: 0v
Pin7: 0v
Pin8: 12.23v
Pin9: 0.296v
Pin10: 0.04v
Pin11: 0.14v
Pin12: 0.017v
Pin13: 0.373v
Pin14: 0v
Pin15,16: 0.014v

any suggestions?

MOD EDIT: Link to schematic and boardview -> https://www.badcaps.net/forum/showthread.php?p=1240393
.

[mon2]

Re: Lenovo ideapad 5 - identify shorted chip

Remove all power. Meter in resistance mode.

Measure the resistance to ground of:

Pin # 16 (LX2)
Pin # 13 (LDO)

[s_henya]

Re: Lenovo ideapad 5 - identify shorted chip

Remove all power. Meter in resistance mode.

Measure the resistance to ground of:

Pin # 16 (LX2)
Pin # 13 (LDO)

Pin13: 1.7ohm
Pin15,16: 2ohm

that's probably bad :-(

[mon2]

Re: Lenovo ideapad 5 - identify shorted chip

See attached.

1) Flux and remove PC414. Measure the resistance to ground again after removing this capacitor. No power during the resistance checks.

2) Flux and lift one leg (carefully) of the inductor @ PL402. Measure the resistance to ground again after removing this capacitor. No power during the resistance checks.

Which side of the circuit is with the low resistance after lifting the one leg of PL402?

3) Do you have an adjustable power supply that can support 1 volt?

4) Be sure that the replaced component is properly soldered. As a suggestion, flux and reflow the part well enough with low air pressure but spin the hot air tool in circles from the topside. Eventually, the solder will be in liquid form and allow for this component to swim onto the PCB pads and 'align like soldiers'. Louis, Alex and others have some great YT videos that demonstrate this process.

[mcplslg123]

Re: Lenovo ideapad 5 - identify shorted chip

Before ordering/soldering a new IC, basic things has to be checked. Else new ic may also get damaged. Since you have shorting on 3v LDO line very very likely SIO is shorted.However, one can be sure with voltage injection as advised by@mon2.

[s_henya]

Re: Lenovo ideapad 5 - identify shorted chip

@mon2:
1. Removed cap from LDO line-> resistance is 1.3ohm to GND
2. Removed coil from LX line-> resistance is 1.5ohm on the pad to other side of the IC
3. I have. which point do you recommend me to inject the 1v?
4. Confirmed, it is my 1st time to replace QFN chip, but plenty of experience with soldering and reflow. so this one went smoother than expected. Alex is indeed very professional at his work :-)

@mcplslg123 i agree i should have tested, but i was hoping for an easy repair- i really hope the SIO is good, i don't believe i will find a pre-programmed IC.
Replacement MB is kinda pricy since this is i5 10th gen...

[mon2]

Re: Lenovo ideapad 5 - identify shorted chip

So it appears that you have 2 shorts linked to this regulator.

LDO rail is shorted.

Downstream switching regulator leg is shorted.

Be sure the QFN device is properly soldered, do check the resistance between the pins on this IC to confirm the LDO pin is not shorted with another.

After the above, consider to dial up 1 volt on your power supply.

Red probe of the power supply onto the LDO rail; black to ground. No other power sources should be applied.

Then monitor for which part heats up with this injection. Ok to increase the current but keep the voltage at 1 volt for now.

Same method can be used for the switching regulator leg where you have lifted the coil.

Hoping that a local capacitor heats up and is the root cause of the fault.

[s_henya]

Re: Lenovo ideapad 5 - identify shorted chip

Seems like indeed 2 different shorts..
Will attempt voltage injection and hope it's only a cap.
Hope it's not the SIO or a mosfet going to the cpu or gpu.
Will update tomorrow!

[mcplslg123]

Re: Lenovo ideapad 5 - identify shorted chip

Seems like indeed 2 different shorts..
Will attempt voltage injection and hope it's only a cap.
Hope it's not the SIO or a mosfet going to the cpu or gpu.
Will update tomorrow!

Unfortunately, its the SIO that's very likely going to heat up.

[s_henya]

Re: Lenovo ideapad 5 - identify shorted chip

I injected 1v on the LDO line. Current consumption was only 0.3amps.
I couldn’t feel anything warm on the board.
(Unfortunately i dont own a thermal camera) but i touched the SIO and didn’t feel anything abnormal.
Due to the risks of burning the CPU/GPU I can’t raise more than 1v right?
So i guess this is game over?

[mon2]

Re: Lenovo ideapad 5 - identify shorted chip

No. Locate the CPU power rail. Remove all power.

Meter in resistance mode. One meter probe here on this shorted rail. Other meter probe on the CPU power rail.

What is the resistance between the 2 points?

[s_henya]

Re: Lenovo ideapad 5 - identify shorted chip

Should i check on the coils or at the input of the mosfets?

[mon2]

Re: Lenovo ideapad 5 - identify shorted chip

Coils will be fine. This check will confirm if there is a leaky high side mosfet.

[mcplslg123]

Re: Lenovo ideapad 5 - identify shorted chip

AFAIK, @mon2, a leaky high side mosfet will affect 19V rail and not 3V LDO rail.

[Sephir0th]

Re: Lenovo ideapad 5 - identify shorted chip

I don't want to be the one who is stopping the fun here but I don't see the point to dig in elsewhere, if there is a high chance the PCH is shorted from +3.3VALW rail.