Lenovo Ideapad 700-15ISK shuts down shortly after it starts. Works on battery

[ZixuTech]

Hi Guys, a weird case here.
This laptop came with damaged hinges, but no liquid signs.

It will loop between battery charging/not charging/charging/... Now the original battery is completely drained it won't turn on with it. The orange light keeps blinking nonstop.

I have replaced the battery with a newly charged battery and it turns on but doesn't charge. The orange charging light blinks three times indicating charging issues.



I have replaced bq24780S battery charging chip, no difference.
With a connected new battery, it doesn't pull any current. When turning it on it pulls 0.89A and stays on. Although sometimes it will turn on and off within a sec if the battery was connected for the first time.

If I hold the power button and switch it off, falls down to 0A current pull.

Strangely without a battery, it turns on for a sec and shuts down. I can see pulls up to 1A from before it shuts.
I cannot detect any shorts on the coils. I wonder if this model requires a battery as a backup to fire up.

Without heatsink and battery, I can see under IRCam the CPU and GPU heat up for a sec, which means all voltages are OK.

PLT_RST# jumps to 3.4V within that sec until it switches off.

Made a video here https://drive.google.com/file/d/12Ri...ew?usp=sharing

Went through voltages from the power sequence with a power button pressed and no battery. They come alive for a sec until S0 lines.

Is it normal for this model not to turn on without a battery? If the battery is not charging, why does it pull close to 1A and drain the battery at the same time? Windows show the battery not charging.

[reformatt]

Re: Lenovo Ideapad 700-15ISK shuts down shortly after it starts. Works on battery

ACFET/RBFET condition? Any issues in this area the BQ chip disables charging (read the datasheet).

[mon2]

Re: Lenovo Ideapad 700-15ISK shuts down shortly after it starts. Works on battery

Voltage on pin #28 = Vcc is too low.

Connected to this pin is a low resistance series resistor (~10 ohms). Confirm the resistor value with all power removed.

Next are 2 diodes that you can see in your posted pic.

Check that each diode is ok with no power, meter in diode mode.

Then with battery connected, measure the voltage input to the diode, voltage output at the common cathode of the 2 diodes but before the series resistor.

Vcc is too low after this group of parts.

Start with this review. The TI data sheet for this charger IC is very useful as it offers a reference design example and details under which the charger IC will charge, etc.

[ZixuTech]

Re: Lenovo Ideapad 700-15ISK shuts down shortly after it starts. Works on battery

Thanks @reformatt these FETS were providing good voltage.

@mon2 that seems to be it, somehow resistor value went from 10Ohm to 100K, hence the voltage was not enough.

Also turns on without a battery now.

The Orange light seems to stay stable now, with the battery and pulls up to 2A.
However, I lost the picture on the internal and external screens. No response from the capslock. The keyboard backlight briefly comes on when starts up.

Voltages on coils seem to be present apart from 1V_VCCGT which is 0V with connected LCD. I assume this should be 1V. All voltages here seem to be OK apart from PWR_VCCGT_PWMA, which seems to be coming from ISL



3D3V_VGA_S0 - 3.3V
LCDVDD - 3.27V
1D05V_VGA_S0 - 1.05V
PWR_VGA_CORE - 0.9V
1V_CPU_CORE - 0.98V
1V_VCCGT - 0V
1V_VCCSA - 0.98V

[mon2]

Re: Lenovo Ideapad 700-15ISK shuts down shortly after it starts. Works on battery

Good to hear of some progress.

1V_VCCGT - 0V

This is concerning. This is a voltage rail used by the CPU.

Remove all power. Meter in the lowest resistance scale.

Measure the resistance to ground of 1V_VCCGT @ PL4802, pin # 2.

If the resistance to ground is very low - the CPU may be defective.

[ZixuTech]

Re: Lenovo Ideapad 700-15ISK shuts down shortly after it starts. Works on battery

Thanks for your efforts @mon2
In Ohm scale on my Fluke, it shows:

1V_VCCGT - 4.91 Ohms
1V_CPU_CORE - 2.87 Ohms
1V_VCCSA - 13.58 Ohms

CPU seems to heat up, but Chipset emits more heat than CPU and GPU at 37*C

Also, PU4702 (1V_CPU_CORE) seems to almost hit 48* while PU4801/2 are dead cold at 0.8A draw.

[piernov]

Re: Lenovo Ideapad 700-15ISK shuts down shortly after it starts. Works on battery

https://logi.wiki/index.php/User:Pie..._I_solve_it.3F

[ZixuTech]

Re: Lenovo Ideapad 700-15ISK shuts down shortly after it starts. Works on battery

Thanks, @piernov that makes sense. Although this is 1V_VCCGT on the CPU coils.

Any other suggestions on where else to look. Currently, it turns on, the keyboard lights up for a second, orange light shows battery charging. Fans are spinning, pulls almost 1A. Cpu, GPU, and chipset is warming up.

However, No beeps or post signs and no internal or external display.