Acer KAV10 short circuit on jack

[rippergr]

Hello all,
I have an acer kav10 netbook REV 1.0 which doesnt power on ,no lights,nothing it's completely dead.

When I use my bench power it short circuits if the voltage goes over 2,5V.
If I put 2V I can measure components, in this case I have in VIN (measuring in dc jack + ) 1,20V . In pd13 I have from the side of VIN 1,20V and on the other side 0,85V. Almost everywhere I measure (PQ10,PQ44 etc) Ihave 0,85V .
In PU5 CSIN I have no voltage.

There is no visual defection on any component.
Can someone help me out?

[tibd]

Re: Acer KAV10 short circuit on jack

I would start turning up the voltage supply gradually and see if anything heats up. You are safe up to the nominated voltage the original PS provides.

[rippergr]

Re: Acer KAV10 short circuit on jack

I thought of that but when I increase the voltage over 3v my bench power supply just cut the voltage, increases the ambs a little and light a red LEDs showing that there is a short. So I can't get past 2,8 - 3v

[rippergr]

Re: Acer KAV10 short circuit on jack

I think the problem is with PQ10 P1403EVG_SO8.
I tested with multimeter and it gives me short on every pin (multimeter set to beeper)
Can I inject voltage after the mosfet to some point and what voltage so I can check if is indeed this mosfet?

[rippergr]

Re: Acer KAV10 short circuit on jack

I changed the mosfet and the short circuit is gone.
The laptop still doesnt power on and the mosfet is very hot when I give 19V on jack.
In pins 1,2,3,4 I have 19V and in 5,6,7,8 I have 0,3V so I think it has another defective component.
Can someone guide me what else should I check?

[rievax_60]

Re: Acer KAV10 short circuit on jack

Hopefully a shorted surface mount ceramic capacitor on the B+ rail. Sometimes it's a shorted high side MOSFET usually in the Vcore regulator.

[rippergr]

Re: Acer KAV10 short circuit on jack

So I should check PC147,PC156 and pc 42,43,44?
How can I check if a capacitor is bad or short?

[rievax_60]

Re: Acer KAV10 short circuit on jack

I went to sleep.
First check with your meter to confirm that it is an ohmic short, a few ohms or less.
If you decide to apply power to the B+, apply no more than 1 volt to avoid more damage although this may have already occurred. Look for any shorted High Side MOSFETS that are trying to pass the B+ voltage directly to the low voltage rail that they are supposed to supply, like +CPU_CORE and others.
If it is a shorted capacitor, I use a method that requires a multimeter that has 10uv resolution. I use it to trace voltage drops on the ground plane. Other members use easier to understand methods.

[and555]

Re: Acer KAV10 short circuit on jack

Can I inject voltage after the mosfet to some point and what voltage so I can check if is indeed this mosfet?

yes, you can inject voltage after the mosfet, as rievax_60 said: apply no more than 1 volt.