Lenovo IdeaPad 5 ITL05 | LA-K321P | Liquid Damage & No Charging

[grimacelord]

Hello,

I have an LA-K321P board here that came to me for no power. Upon visual inspection of the board, I found some liquid damage around PQB13 area. Replaced PQB1, PQB2, and PQB13. Laptop will power on if the battery has a charge, but the computer will not charge the battery. USB Type C meter shows 20V being negotiated, but virtually zero amp draw (0.0100 at most that appears for a brief second about once every 5 seconds or so). Looking through thermal camera, UT1 (SN2001024YBGR) is getting hot. I have schematic, but no board view. Was hoping someone could help me get this charging


Link to schematic: https://www.badcaps.net/filedata/fetch?id=2100910

[grimacelord]

Not really sure what to even check after I've replaced those few components that had visible liquid damage...

[mon2]

Can you post a pic of your board for this region? My BV looks different than yours.

[grimacelord]

Can you post a pic of your board for this region? My BV looks different than yours.

Hopefully the quality is sufficient. Thanks, mon2!

[grimacelord]

Any ideas, mon2? I'm stumped.

[Kridan]

I am having the same problem on a Ideapad, altso i notice one pair of cells voltage of about 6.4v at the charging port, so it actually backfeeds voltage from the battery out the charging port, otherwise same problem, charging voltage goes in, with battery in it starts and says its charging but its not, it's drawing a minuscule amount of power.

Did you ever find a solution?

[mon2]

Missed the follow up on this thread.

Remove all power. Meter in resistance mode. Measure the full path resistance of the battery charge circuit. Measure directly on the charger IC @ PUB1, pin # 19 & # 20.

This full path resistance should be ~20 ohms. Confirm it.

[grimacelord]

Missed the follow up on this thread.

Remove all power. Meter in resistance mode. Measure the full path resistance of the battery charge circuit. Measure directly on the charger IC @ PUB1, pin # 19 & # 20.

This full path resistance should be ~20 ohms. Confirm it.

Forgive me, but I am a bit confused on the instructions. I have found charger IC @ PUB1. Are you wanting me to measure the resistance between pin #19 and PRB19 and then pin #20 with PRB18?

[mon2]

Correct. Sometimes / often, the resistance between these 2 pins is not matching the schematic values. Then the charger IC believes there is too much of a load in the charging process so the charging is halted.

[grimacelord]

Correct. Sometimes / often, the resistance between these 2 pins is not matching the schematic values. Then the charger IC believes there is too much of a load in the charging process so the charging is halted.

I'm getting 10.6 ohms on both.

[grimacelord]

Correct. Sometimes / often, the resistance between these 2 pins is not matching the schematic values. Then the charger IC believes there is too much of a load in the charging process so the charging is halted.

I may have measured wrong because I I was misunderstanding what you wanted me to measure. Resistance mode, one probe on pin 19, the other probe on pin 20, I am measuring 21 ohms. One probe on pin 19 and other probe on PRB19 is 10 ohms and same with the other. Hope that clarifies. Sorry for the confusion

[mon2]

Does this model offer a traditional barrel / coax power connector @ JDCIN1? Have you attempted to power the board using this method? Does it allow for charging?

The battery charger path resistance is within specification and is fine.

[grimacelord]

Does this model offer a traditional barrel / coax power connector @ JDCIN1? Have you attempted to power the board using this method? Does it allow for charging?

The battery charger path resistance is within specification and is fine.

Sorry for the late reply. I became busy with other repairs.

No, this model does not have a coax/barrel charger. It uses USB Type C only.

EDIT: My mistake. There is a coax/barrel connector on the board it just didn't come with one installed and the hole in the side of the bottom panel isn't there to allow for a charger of this type to be connected. I would have to connect a DC-Jack and then drill the hole in the bottom panel if it worked....

[grimacelord]

Wow. I just connected power through a USB-C meter to take some measurements and I saw a puff of smoke. Looked and see DT8 is now charred. Part CESD2510UC3V3U. Seems to be ESD protection. Coincidentally, this sounds very similar to another post I was following where you helped someone else with a similar problem, mon2. That post can be found here.