Lenovo Flex 14" LF14M not power on, Low voltage

[tsiga]

Hi there..

Lenovo flex 14"
LF14M
13281-1
I've got a problem with this laptop, wich is not power on. When i plug adapter i can hear some buzzing sound(charger) and the PU4501 it will be hot. I replaced it with new one, same problem. But, the main problem is in the 20V(primer VIN)circuit I measured just 9.1V. I tested the marked components with multimeter, it is ok.

I think the charger ic(Bq715) is cause the problem..
Any idea? Thanks in advance.

[mon2]

Re: Lenovo Flex 14" LF14M not power on, Low voltage

Hi.

1) remove the battery and work only with the external adapter. Same results?

2) do you have the schematic and boardview files for this logic board? Please post them here if you do. Will check my database as well.

3) is this a standard barrel style power adapter connector? Can you use a lab power supply to confirm the adapter is not the issue?

4) with the power off, measure the resistance to ground on the rails that are at 9v1. Value in ohms?

Are the coils for this ic that is getting hot on the back side? Please take some pix of the back side of this same area.

5) any liquid damage or logic board one day did not power on?

[tsiga]

Re: Lenovo Flex 14" LF14M not power on, Low voltage

Hi.

1) remove the battery and work only with the external adapter. Same results?

2) do you have the schematic and boardview files for this logic board? Please post them here if you do. Will check my database as well.

3) is this a standard barrel style power adapter connector? Can you use a lab power supply to confirm the adapter is not the issue?

4) with the power off, measure the resistance to ground on the rails that are at 9v1. Value in ohms?

Are the coils for this ic that is getting hot on the back side? Please take some pix of the back side of this same area.

5) any liquid damage or logic board one day did not power on?

Hi!
1)Yes,
2)yes, i have, but not for this version.. I was attached the file.
3)I tried both, same issue..
4)I measued in PU4406 drain side:~5Mohm, Source: 17Kohm
i took some picture.
In freeze test only the pwm ic getting hotter.
5) no liquid damage or viewable damage, my client says: 'not happened anything'

Thank you

[mon2]

Re: Lenovo Flex 14" LF14M not power on, Low voltage

Power down and measure the resistance to ground on each grey coil on the backside. Perhaps one of these rails is with an issue that is leading the local switching regulator to heat up.

It is very possible for the switching regulator to be damaged now but the question is why did this happen?

[tsiga]

Re: Lenovo Flex 14" LF14M not power on, Low voltage

Power down and measure the resistance to ground on each grey coil on the backside. Perhaps one of these rails is with an issue that is leading the local switching regulator to heat up.

It is very possible for the switching regulator to be damaged now but the question is why did this happen?

Measured resistance in coild 3.3V alw: 250ohm 5V alw: 570ohm
I tried inject 5V /3.3V circle. 5V circle picks up 0.03A from lab power supply. the 3.3 circle picks up 0A