Lenovo L15 Gen 3 type 21C7 AMD no charge, no power

[ATS-Byron]

Hi All,

I tried two different power adapters.

On the lines that are marked as 20V on the boardview, I only have 5V. But there is no light that comes on at all when this think is plugged in.

Customer stated that it just stopped charging and then when the battery died that was it.

I have a suspicion that it could be U7303 which I believe controls the voltage setting for the adapter? Markings are RD LYBK CVEB

Any help would be appreciated!

[ATS-Byron]

Hi,

Has anyone had any experience with this series of laptop and can give me a couple ideas on where to find the parts or the steps for diagnosis?

[mon2]

Link the schematics if they are available but only inside the dedicated schematic forum, not here.

How is this laptop powered? USB Type C power adapter? If yes, then there will be a usb power delivery controller in the power path to power this logic board. This PD controller must work with the power adapter to dial up the 20v power delivery contract to power the board and charge the battery.

If you are stuck at 5 volts then the CCx (CC1 and CC2) lines used for this communication must be reviewed.

Do test by flipping the power adapter connector by 180 degrees and test again. Any difference?

Do you have a USB type c meter? What is the current draw? Is it a static value on the current draw?

Remove all power, meter in diode mode. Red meter probe (yes, red) to ground. Black meter probe to CCx pin. What is the measurement?

Next check the other CCx pin on the same connector. Post each measurement.

[ATS-Byron]

Link the schematics if they are available but only inside the dedicated schematic forum, not here.

How is this laptop powered? USB Type C power adapter? If yes, then there will be a usb power delivery controller in the power path to power this logic board. This PD controller must work with the power adapter to dial up the 20v power delivery contract to power the board and charge the battery.

If you are stuck at 5 volts then the CCx (CC1 and CC2) lines used for this communication must be reviewed.

Do test by flipping the power adapter connector by 180 degrees and test again. Any difference? There is no difference when I flip the usb-c end. I have tried with two Lenovo OEM chargers. The ones that come with the laptop.

Do you have a USB type c meter? What is the current draw? Is it a static value on the current draw? I don't have a usb-c version but did order one to check this.

Remove all power, meter in diode mode. Red meter probe (yes, red) to ground. Black meter probe to CCx pin. What is the measurement? USB-C #1 CC1 is - 0.685, CC2 is 0.683. USB-C #2 CC1 is 0.637, CC2 is 0.636

Next check the other CCx pin on the same connector. Post each measurement.

Sorry for the delay, been very swamped with work lately. Thank you for your help on this.

[ATS-Byron]

Hi, bump. Any idea on the numbers I posted?

[mon2]

The diode readings are ok and not showing any shorts.

I don't have a usb-c version but did order one to check this.

What is the voltage and current draw when connecting to the logic board? Also test by flipping the power head by 180 degrees. Same measurements?

[ATS-Byron]

The diode readings are ok and not showing any shorts.



What is the voltage and current draw when connecting to the logic board? Also test by flipping the power head by 180 degrees. Same measurements?

Hi, I just picked up the tester today. It shows 5.049V and 0 amps on both USB-C ports, and both ways on the power coming in. And that is with or without the battery plugged into the motherboard.

Thanks.

[mon2]

You are drawing no current (0 amps). Voltage is the power on default on the external power adapter. For power delivery adapters such as yours, there must be a proper communication (handshake) between the logic board and the external power adapter over the single wire CC1 or CC2 line. One such contact exists on each side of the Type C connector so that you can rotate the head by 180 degrees and the adapter can still spit out the requested voltage / current paired power delivery contract to power the logic board.

Given that the current draw is @ 0 A, start by checking the fuse @ F4202.

Remove all power. Meter in DIODE mode. Short the meter probes and you should hear a tone beep. Then apply the same meter probes across F4202. If the fuse is not blown, you should hear a tone beep. Then check the other fuse @ F4201 and F4301.

[ATS-Byron]

You are drawing no current (0 amps). Voltage is the power on default on the external power adapter. For power delivery adapters such as yours, there must be a proper communication (handshake) between the logic board and the external power adapter over the single wire CC1 or CC2 line. One such contact exists on each side of the Type C connector so that you can rotate the head by 180 degrees and the adapter can still spit out the requested voltage / current paired power delivery contract to power the logic board.

Given that the current draw is @ 0 A, start by checking the fuse @ F4202.

Remove all power. Meter in DIODE mode. Short the meter probes and you should hear a tone beep. Then apply the same meter probes across F4202. If the fuse is not blown, you should hear a tone beep. Then check the other fuse @ F4201 and F4301.

Ok, so all three fuses are good.

What would be the next step sir?

Thanks.

[ATS-Byron]

Ok, so all three fuses are good.

What would be the next step sir?

Thanks.

Bump.. 😊

[mon2]

I am suspecting that the you are @ 5 volts due to the lack of power delivery negotiations between the logic board and the external USB Type C PD supporting power adapter.

The PD controller on the logic board resides @ U7201 and is usually a stand-alone component. That is, U7201 needs to be reviewed if you do not see 20V being negotiated. Review for possible damage. Review the onboard LDO rails to confirm they match the values shown in the schematics. The power delivery communication is over the CC1 and CC2 lines (depending on which side of the active blade on the USB connector is used).

A valuable tool to have will be a PD analyzer and / or PD meter. Some of the new models offer the details of the PD contracts and which contract is negotiated after the handshake. This information will allow us to conclude that the PD controller @ PU7201 is working as expected.

Summary - we need 20V to be negotiated so that PU4401 is pacified and allows for the logic board to be powered up.

Carefully review the voltage to ground of the following points of interest:

PU4401 (Charger IC)

VBUS ; pin # 1
ACP ; pin # 3
ACN ; pin # 2
CHRG_OK ; pin # 4
REGN ; pin # 28

[ATS-Byron]

Afternoon, I am waiting on the PD analyzer to show up as I have not had one before.
I don't know that I have the right schematics to check the onboard LDO rails?

But here are the voltages to ground for these:

VBUS: 4.987
ACP: 4.987
ACN: 4.987
CHRG_OK: 0.000
REGN: 4.984

Thanks

[ATS-Byron]

Afternoon!

I finally took the time to hook up the PD analyzer to my computer and the offending board, but I have no idea of what I am looking for. The one port shows nothing when I start recording, and the second port shows information that means nothing to me. This is my first foray into PD data.

I have the CY4500 EZ-PD analyzer if anyone can help with that.

Byron

[ATS-Byron]

I guess a bit more information would be nice.

When the analyzer is running both ports read this: CC1: 8mV CC2: 1,567mV V:4.850mV A:25mA or less

But port one doesn't show any data readings, and port two does. Not sure what format works, but the PD analyzer exported the .csv file attached.

Thanks.

[ATS-Byron]

Bump 😁

[mcplslg123]

The port which is not offering any data may be dead/bad. Usb-c ports itself go bad very often. Try cleaning the port with sharp needle/tweezer and IPA. No power attached while cleaning.

[ATS-Byron]

Good morning. I cleaned the ports. And still nothing. Both ports are showing nothing, so they are both dead/bad.

I will replace both ports and see what happens.