Lenovo X240 NM-A091 MEC1633L - dead no power

[magneh]

Hi there

I have 2 Lenovo X240 NM-A091 , and I'm trying to fix at least one of these.

BOard is dead, no boot, but I dont have the full machine assembly.

Connected 20V on main power rail, no short.
Shorted PW_SW near EC controller, and board started to consume 74 mA
The MEC1633L is getting hot.
Found 2 caps shorted connected to this IC. (in red)

Should I blame the microcontroller and try to replace and program it?

Also noticed a quite low resistance value in L4, 45 ohm , not sure if its a reasonable value or not...
Maybe someone with some experience in Lenovo motherboards here that could help?

Thanks!

[piernov]

Re: Lenovo X240 NM-A091 MEC1633L - dead no power

Sounds like the MEC1633L is partially shorted indeed… You either need to take it off the same model donor board or buy a blank chip and program it with an EC programmer.

Btw for it to work properly you need to use a Lenovo AC adapter of sufficient power rating, it has a center pin for identification by the EC. Or you can at least solder a resistor (for exemple 550 ohms for 90W AC adapter) between what connects to the center pin on the board and ground.

[magneh]

Re: Lenovo X240 NM-A091 MEC1633L - dead no power

Hi Piernov!

Thanks for your inputs.

I think I can get an exact same motherboard to try to get the MEC1633L and replace it.

Ive seen that this IC comes with a lot of underfill under it.

What do you guys recommend to remove this without breaking the IC?
200°C and scrape the underfill from the chip and then reball it?

Thank you once again!

[mcplslg123]

Re: Lenovo X240 NM-A091 MEC1633L - dead no power

Its a BGA IC-so should be removed with a bga rework station.With a hotgun 200 celsius may not be sufficient.

[magneh]

Re: Lenovo X240 NM-A091 MEC1633L - dead no power

Yes, but Im talking about the temperature of the hot hair to remove that nasty underfill from the chip

Ill test with 200 and see if it works.

And If I dont rip any pads

[piszpunta]

Re: Lenovo X240 NM-A091 MEC1633L - dead no power

broken elements:
r1115
r1116
r1117
r1118
what parameters to use resistors?

[evrensel]

Re: Lenovo X240 NM-A091 MEC1633L - dead no power

Hi Meganeh,
Did you manage to solve the problem? I am having exactly the same problem with my Lenovo X240. I will appreciate any help .
Thanks!