lenovo t430s no power

[kammy6000]

hello, i have lenovo t430s since can not get schematics closest is t430 schematic but i have check all the fuses and all seem ok
but not powering on at all no led power light no nothing

this board has separate power sub board and look like have burn mark on some the copper lines where it connects to mainboard but still connecting ok , 19v reaches fuse f2

connected to powersupply and not drawing any amps at all
power button is on keyboard on this model

i also notice the sub power board have little switch like a push switch maybe its does nothing probably

any help please

[Techtiger]

Re: lenovo t430s no power

check the voltage on fet Q36 Q9 all legs Drain/Source/Gate find out the voltage of ACDC ID Schematic T430

[kammy6000]

Re: lenovo t430s no power

hello thanks for reply

Q36 mosfet has on 4 legs 0.02 0.02 0.03 0.02 and gateside has 0.83 on both connection
is it died?

thanks

[Techtiger]

Re: lenovo t430s no power

check fet Q9 all legs most pro 1st fet not switching on +19V check for short with out power in DIODE mode

[kammy6000]

Re: lenovo t430s no power

ok on the first fet i get resistance 567 all 3 legs 4th leg 0.00

on second fet no resistance on any leg , so this means ? thanks

[peste]

Re: lenovo t430s no power

From the picture,chip bridge network NS692412 SOP24, seems to have problems.

[kammy6000]

Re: lenovo t430s no power

yes you right this has been removed because it was dead and laptop not have any Ethernet connection but this problem happened after that because this board has subboard so the sub board came loose while power was applied i think that damaged a chip somewhere causing the power issue

[kammy6000]

Re: lenovo t430s no power

this is other side sir

[digitalpc]

Re: lenovo t430s no power

check first 2 mosfets any short or voltages?

[kammy6000]

Re: lenovo t430s no power

ok so Q36 is shorted as gets warm and dissolves alcohol fast thanks

[springer]

Re: lenovo t430s no power

ok so Q36 is shorted as gets warm and dissolves alcohol fast thanks

Yes my t430s had same issue. Q36 got hot to touch. And output of Q36 was shorted to ground. However, looking at schematic, there was no way for Q36 itself to short to ground directly. So something tied to output of Q36 was shorting to ground. In my case it turned out that one of the big caps (C234) was physically deteriorated looking and was also hot to touch. Once C234 was removed, short on Q36 disappeared resolving the issue.