240 and 9240 can they be checked with DVM?

[semi932]

Think I got some bad irfp 240's and 9240's.
Just for experiment I used diode function and measured from Source to G and D.
On some I get about .450v give or take for brevity.

Others I get one measurement and OL from S to G.
These I think are bad.

Does this make any sense or am I grasping for straws?

[Marra]

Hope this is helpful :- MOSFET testing

[h_a]

From above link

On most multimeters (but by no means all!) this puts about 3-4v across the device under test.

I doubt any quality meter will do that. Even if it did, turn-on voltage of the P-channels goes up to 4.5 V, so outside this range.

You can only check wether the gate is shot by measuring resistance from gate to source (or drain), it should be a large number like Megaohms or similar.

Otherwise there is not much reasonable way to test them (to my knowledge at least) without building a little circuit around the fets to measure drain-current, gate-voltage and, ideally, gate leakage current.

Hannes

[semi932]

Thanks but got some direction on another forum.
I'll link to it so all can see whether it suits them.

Can hexfets be checked with a dvm? - AudioKarma.org Home Audio Stereo Discussion Forums

[nigelwright7557]

In my experience of many faulty mosfets they been short D-S.
I had only one that was short G-S.

[flg]

Yes, Nigelwright has a point I agree with. However, excluding the occasional short cuirict insident, blowing the G-S oxide (ussually greater than 15-20V) is easy in an ESD rich atmosphere like the carpeted area of your house
That would make the G-S low resistance but maybe at somewhat higher voltage than the ohm-meter uses.

[Blues]

Originally Posted by semi932

Think I got some bad irfp 240's and 9240's.
Just for experiment I used diode function and measured from Source to G and D.
On some I get about .450v give or take for brevity.

Others I get one measurement and OL from S to G.
These I think are bad.

Does this make any sense or am I grasping for straws?

Using the diode function you can check the D-S junction diode's integrity (N-type neg probe on D; P-type pos probe on D). It should be around 0.6V like any silicon diode junction.

A mosfet that already let out its magic smoke will have this diode junction fused together and will register a 0.0V reading.

[h_a]

Using the diode function you can check the D-S junction diode's integrity

Yeah, true that's something to try.

Hannes