How to check for short circuit

[arieshenri]

Hi Guyz,

I have a short circuit problem. When adapter plugged in the voltage of the jack adapter messed up. But when I took off NIKOS P2003EVG (P-Channel Fet Enhanced), the voltage going in is good.

The questions is how to to check for the faulty components? or how to check the + or - shorts? Example in capacitor? or in transistor ?

Anyone can help me please.. i have both digital multi meter and analog multi meter...

schematic diagram of the laptop also have...

[severach]

Re: How to check for short circuit

That MOSFET has many pins that are supposed to be shorted so download the P2003EVG datasheet and test the pins that aren't supposed to be shorted. Keep in mind that if you charge the gate right then the part will appear shorted from Gate to Source even though it is functioning correctly. Read up on MOSFET testing because they are a bit trickier to test than BJT transistors.

Then test the pads on the board to see if they are shorted. If the MOSFET isn't shorted and the pads are then you need to look farther down the line.

I test for shorts on the DMM diode scale. Short the leads to see what a short is supposed to read on your DMM. Other people test with the ohm scale.

A short is a short whether in our out of circuit and a shorted part produces phantom shorts in all parts that are in parallel so don't go pulling parts until you've tested a lot. Knowing what all parts show as shorted helps give you an idea of what to pull first.

Ceramic and Tantalum SMD caps are good places to check for shorts.

[momaka]

Re: How to check for short circuit

Keep in mind that if you charge the gate right then the part will appear shorted from Gate to Source even though it is functioning correctly.

You mean Source and Drain?

With the gate not charged, some MOSFETs may also show a diode reading between Source and Drain (since Body is usually tied to Source). If I remember correctly, for N-type MOSFETs, the diode reading will appear as if the Drain is the cathode and the Source is the Anode. For P-type MOSFETs, it's the other way around.

If the Gate is charged as severach mentioned, then you may get a short-circuit between Source and Drain rather than a diode reading.

[severach]

Re: How to check for short circuit

Yep, that would be source and drain. The body diode always conducts but not as a short unless burned out.