Pls help

[frysts]

I need to test power mosfet on my dell lcd, can someone tell me how to test a power mosfet . I have a multimeter

[Rtech]

Re: Pls help

is it a transistor type with 3 legs OR a chip with 8 legs,and a part number would also be helpful ?/

[frysts]

Re: Pls help

is it a transistor type with 3 legs or a chip with 8 legs,and a part number would also be helpful ?/

transisitor type with three leg it look much like a shortkey diode

( how to test a power mosfet in lcd)

[budm]

Re: Pls help

P/N of this MOSFET? N-channel or P-channel?
With the tab up and legs down.
Left pin is the Gate, middle pin is the Drain, the right pin is the Source.
We can only check for shorted only since MOSFET is a normally open device with an exception if it has protection diode between Source and Drain, or Gate protection diode between Gate and Source.
So for now, just measure the resistance between
G & D
G & S
S & D

[Khron]

Re: Pls help

Actually, you *CAN* kinda-sorta check a MOSFET, if you have a diode-check range on your multimeter. Might not work in 100% of the cases, but it's useful at least as a "double check".

(In the case of an N-channel MOSFET)

1) Black probe on the Source leg
2) Touch the Gate with the red probe (to charge it and "open" the FET), then move it to the Drain pin

You should see a reading of a few mV on the meter, which may slowly, or may not increase within the following few seconds.

3) Then short the Gate to the Source pin (with a wire or a resistor leg or whatever).

Now put the red probe on the Drain again (black's still on the Source), and you should get an "out of range" reading.

Still in the case of an N-MOSFET, with the red probe on the Source and the black probe on the Drain, you should get a reading of 0,5-0,7V on the diode check setting. If this is the case, the "body diode" is still working as such. If it were shorted, the reading would be a lot closer to [zero].

For P-channel MOSFETs, the same method applies, but the positions for the red and black probes from the multimeter need to be reversed