Lenovo Y720 15IKB - ESD Damage any idea?

[juergenb]

Hi,

i might get a faulty Legion Y720 Notebook.
The Notebook has an ESD Error.

With external Fan´s the notebook is useable.

The owner tried to swap HDD vs SSD and had an ESD discharge.

These are the errors

• Both fans are not working

• battery doesn´t charge at all, runs from PSU

• HDMI output is not ok

• keyboard light is missing

• no sound from speaker

• webcam is off

Maybe bluetooth is although faulty (not tested)

Has anyone repaired this ESD Damage (can this be repaired)?

Thanks in advance

Jürgen

[Sudoer]

Re: Lenovo Y720 15IKB - ESD Damage any idea?

Fans, battery - it's EC, (for battery also charger and mosfets), keyboard light - another EC (two EC on the board), for HDMI - check U119 IC, sound - audio IC, camera connected to CPU, but the laptop works, so check the camera itself.
So, yes, it can be repaired (most of).

[Brandon Morales]

Hey sorry to revive this post. I'm new to fixing circuit boards and am excited to learn. I just inherited a dead Y720 with what the previous owner stated. Only difference is he said none of that work and one day he opened it up and now it doesn't turn on. I narrowed down where the issue begins and it's here:

One of the MOSFETs (circled in green) input has 20v output shows 0. And then the chip in red gets really hot. So I'm assuming that's where the short is. But I'm not sure what the name of that chip is or if there is anyway to figure out if that is where the issue is.

[mon2]

PQ203 = AON6414A

PU601 = RT6585BGQW

RT6585BGQW Richtek USA Inc. | Integrated Circuits (ICs) | DigiKey

[Brandon Morales]

Perfect! Thank you for that. In your opinion would that be why the laptop isn't turning on?

[mon2]

PQ203 (AON6414AL) is the battery mosfet. This mosfet is acting like a solid-state switch that will enable only if the battery is the sole power source to power the logic board.

Being an N-channel mosfet, the gate pin # 4 will have to be higher (boosted) than the voltage being passed between source and drain pins to enable this component. Once pin # 4 (gate) voltage is boosted, only then will the drain pins (5-6-7-8) offer the battery voltage to power the board.

If the IC @ PU601 is heating up then remove all power. Meter in resistance mode. Measure the resistance to ground of each pin on this IC and compare to the datasheet for this component. Checking for any low resistance to ground which will place a higher-than-normal load onto this regulator. Do review the LDO5 and LDO3 rails which are the 5v0 and 3v3 regulators for low current peripherals onboard. Post your measurements.

This regulator is a very critical one and is creating the 'always on' power rails for the logic board. This regulator is required to get the board to boot.

[Brandon Morales]

I should mention that no battery was in the computer when I got it. So there's no battery in it at all. Everything is straight power. Also I'm looking at the datasheet but can't find where it shows resistance for each pin

[mcplslg123]

Pin3=LDO3
pin13=LDO5

Check resistance to GND on both these pins of PU601.No power attached while measuring resistance to GND.

[Brandon Morales]

This is what I'm getting. Just to confirm and sorry for the dumb question but I need to be in diode mode correct?

LD03 = 1.1
LD05 = 1.3

I also put it in resistance

LD03 = 0.0
LD05 = 1.5

[rogfanther]

Is your multimeter scale in 200 Ohms ? Those two readings for resistance seem do indicate a short on both rails

[Brandon Morales]

I had it set to 2M should I have it on 200

[mcplslg123]

Set multimeter to 20K scale and then measure resistance to GND on both LDO3/LDO5.Note the readings
Next set the multimeter to 200 ohms scale,repeat the measurements.

Share measurement on both scales. However, it seems to me that your LDO3 rail is shorted to GND and not LDO5.

Short to GND on LDO rail could be bad news also as often the PCH part of SOC gets shorted.

First confirm the measurements and if LDO3 is shorted to GND, you need to inject voltage (1V/5A) on LDO3 to find out what is hot.

Very likely KBC and to some extent may be PCH.

[Brandon Morales]

Ok I will measure them later today. But if that is shorted I just need to change that chip? Is that worst case?

[mcplslg123]

Measurements first.

[Brandon Morales]

LD03 for both 20K and 200 show 0.0
LD05 for both 20K and 200 go up and then just show 0L

Am I don't something wrong or is there a short?

[mon2]

LD03 for both 20K and 200 show 0.0

Short your meter probes. Do you see the same measurement as in the above testing? From the posted measurement, you have a dead short on this power rail.

The LDO5 is ok since there is a larger resistance and is confirmed with the 'OL' on the LCD display which means over-limit for the selected scale on the meter.

Would you have an adjustable power supply? Ideally needs to be setup for 1 volt but be able to support 3A-5A for some fireworks. With such a setup, need to apply this 1 volt power supply onto the LDO3 rail (red lead) and black lead to ground. This process will cause the shorted component to heat up or even crack under the pressure.

[Brandon Morales]

How do I short my meter probes? And also sadly I don't have an adjustable power supply. From what I have so far would you say that chip needs to be replaced?

Also side question. How did you know to check LD05 and LD03 and not the other areas? Is it somewhere in the datasheet

[rogfanther]

Just touch the probes together, to "measure" the resistance between them. That is called shorting the probes.

[Brandon Morales]

Hey there, so just to practice my soldering I replaced that chip. However, no power doesn't go past the first mosfet (as shown in picture) one end has 20 v coming in but 0 v coming out I checked the resistance on it using diode mode I get .300 and the mosfet after that I get 1.700. is one of these shorted now?

[mcplslg123]

Why un necessarily keep changing components when its crystal clear that you have dead short on 3V LDO? This will make situation even worse.
You need a adjustable dc power supply to inject 1V/5A on 3V LDO line to find out whats hot.