Samsung powers on with battery, no power with charger.

[diif]

Hello, i have been given a faulty Samsung NP300ESC laptop with a Scala3-15/17crv motherboard to look at. The customer said the old charger died so they bought a new one which was universal. Since then there have been powering on issues. I have measured the voltage on this and it's nearer 20v not the 19v it says. Either it's this or the previous charger have damaged something i think.

There are no LEDs lit when i plug in my power supply and pressing the power button does nothing. However if i plug in a battery the laptop powers on fine.

There is 19v on VCC of BQ735 up near the battery connector, but without a schematic i'm struggling a bit. Can anyone point in the location of where i need to be testing please ? Thanks

[dj_ricoh]

Re: Samsung powers on with battery, no power with charger.

first! like you need to be 100% sure that the DC jack its ok.

90% of the Samsung i do they all bad there and even with cables!

[angel-boy]

Re: Samsung powers on with battery, no power with charger.

See photo , check there, you have 2 i.c , one is shorted .

[Life Goes On]

Re: Samsung powers on with battery, no power with charger.

I don't think it gone be dificult to solve the problem, that gone be for sure in the power line circuit, but you gone need the schematic to solve that.

[dj_ricoh]

Re: Samsung powers on with battery, no power with charger.

take it of and trace it with the multimeter where it comes from.

[dycc]

Re: Samsung powers on with battery, no power with charger.

See photo , check there, you have 2 i.c , one is shorted .

agree with you

[samanthban]

Re: Samsung powers on with battery, no power with charger.

Two fet or dual fet in between 5v and 3v power ic
one of those gone wrong

[diif]

Re: Samsung powers on with battery, no power with charger.

Thanks for your replies.
I have checked the dc socket. I get power on the board from the centre pin, so i know that is fine.
I checked under the tape as indicated by angel-boy and found the 2 ics.
with markings 7200 on one and 9402ygt on the other.
I found no shorts to ground or to its other pins and have measured the voltages.

AON7200
S-75-135mv constantly fluctuating
G-50-126mv constantly fluctuating
D-18.24v stable

9402gyt
S-60-130mv constantly fluctuating
G-60-130mv constantly fluctuating
D-1.03v stable.

[gcomputers]

Re: Samsung powers on with battery, no power with charger.

I repaired Np350E
I found the second 9402 gyt is shorted to measure better to remove it from board , i ordered it on ebay replaced and the laptop works fine.

[angel-boy]

Re: Samsung powers on with battery, no power with charger.

is a simple repair.

Hope that helps you !

[diif]

Re: Samsung powers on with battery, no power with charger.

Yes, a great help, thank you.

A little tinier than normal but i think i'll manage. I just need to see if the customer will wait for them to arrive from China as i can't find any UK suppliers.

[diif]

Re: Samsung powers on with battery, no power with charger.

The parts arrived and i soldered into place. However during the soldering i managed to knock off and lose a small ceramic cap, just above the two ics.
Any idea on a value ? Thanks.