MOSFET 2SK3018 advice

[Steve.B]

I am hoping someone will be able to advise me on this mosfet. I am trouble shooting a circuit on a Panasonic plasma psu - thread here, and have noticed that i have a constant resistance of about 57ohm between the Gate and Source pins on this little fet, (Q422). I have followed the traces on both the pcb and the schematic, and have determined that the resistance is within the fet itself.

Here is a link to the data sheet for the Mosfet, it's the SOT-323 package.

http://www.sztuofeng.com/pdf/2SK3018.pdf

I know nothing about mosfets, but i have noticed that this is the only one i have come across in the circuit where i am getting a constant resistance reading between the gate and source.

Is this a normal reading?, or could i have a problem with this fet?

Any advice will be appreciated. Thanks.

P.S, I used a multimeter for the resistance readings. The board was not powered.

[munirutech]

Re: MOSFET 2SK3018 advice

if you inter change the probe of the meter is it the same reading if yes then is faulty

[munirutech]

Re: MOSFET 2SK3018 advice

make sure to romove it from the ps before testing it

[Steve.B]

Re: MOSFET 2SK3018 advice

Thank you for the replies.

Yes to both of them, whichever way round i have the probes, i still get a 57ohm resistance. I also took your advice and removed the mosfet from the board (though i was certain there was not a path between them on the board). With the part removed from the board, i still get the 57ohm between Gate and Source.

So this fet is no good? Thank you again for the information, i feel i am making progress with the trouble shooting now.

[budm]

Re: MOSFET 2SK3018 advice

It has built-in Gate-Source protection Diode which may be damaged.

[Steve.B]

Re: MOSFET 2SK3018 advice

Thank you budm, i have ordered a couple of replacements, luckily they are easily available. I ordered a couple in case of mishaps when fitting - never fitted one of those tiny SOT-323's before.