Lenovo thinkpad Edge 13 0217 - Spontaneously low NBSWON to 1.5V

[ktmmotocross]

Hello.
Have this Lenovo Thinkpad Edge 13 0217 that normally works but after two/three days it coul not start or when start it shows just logoand shuts down. i found that problem is NBSWON voltage wich goes to 1.5V. i do many things, even cut signal to switchboard and wire it to switch. things little improved but after few days it is back to 1.5V. cannot figure what can be source of this problem. maybe the KBC is bad.

Schematic
https://www.badcaps.net/forum/showthread.php?t=83451

[kodox]

Re: Lenovo thinkpad Edge 13 0217 - Spontaneously low NBSWON to 1.5V

i've just found same problem but it's on Acer board, i thought it was the KBC too but after searching the anomali i found that the 3v (used to pull up) track is somewhere broken in the middle layer of the board, so i tried to inject the voltage (from the 3v_LDO line in my case) and it works like a charm!!!!

maybe ur problem is the same as mine, hope this help...

[ktmmotocross]

Re: Lenovo thinkpad Edge 13 0217 - Spontaneously low NBSWON to 1.5V

maybe, but why some time is ok 3.3V and after time get to 1.5V, but i try to hard wire from kbc to switch

[kodox]

Re: Lenovo thinkpad Edge 13 0217 - Spontaneously low NBSWON to 1.5V

i think the signal line from KBC to power switch is ok, the problem is on 3v voltage on R198 to pull-up that pin high

[ktmmotocross]

Re: Lenovo thinkpad Edge 13 0217 - Spontaneously low NBSWON to 1.5V

i measure resistance across R198 and without battery it have correct 9.9kohm but when i connect battery resistance goes down to 3.1kohm.

[ktmmotocross]

Re: Lenovo thinkpad Edge 13 0217 - Spontaneously low NBSWON to 1.5V

replaced KBC and now i have stable full 3,36V on NBSWON. I give it few days testing as i wrote that fault came after few days

[ktmmotocross]

Re: Lenovo thinkpad Edge 13 0217 - Spontaneously low NBSWON to 1.5V

this shit freaks me out.

replaced kbc and still have leakage that pulls my 3.3V NBSWON down

[kodox]

Re: Lenovo thinkpad Edge 13 0217 - Spontaneously low NBSWON to 1.5V

do u have 3VPCU on R198? if u don't try use a jumper wire to 3VPCU source

[ktmmotocross]

Re: Lenovo thinkpad Edge 13 0217 - Spontaneously low NBSWON to 1.5V

yes i have. when laptop start it jumps to 3.3 but when is off after time somethig start to leak and it goes to 1.5V

[ktmmotocross]

Re: Lenovo thinkpad Edge 13 0217 - Spontaneously low NBSWON to 1.5V

changed pullup resistor 10k R198 to 2.2k and voltage goes up to 2.5V. still not perfect but now it dont make problems