Testing a mosfet with DMM and an ebay smart component tester/ esr meter

[withalligators]

So, I have replaced a number of components on the power board of a TV trying to eliminate some high pitched coil whine. All caps are new, but the whine persists, so now I'm trying some of the other prone-to-failure components.

The Mosfet is a W18NK80Z, and this is the datasheet

I'm using an ebayed ESR meter / smart component tester

and an Ancor 702073 Multimeter to try and test it. When I put it on the smart tester, I get the following readings:

C=12.9nF
Vt=4.2V

and a proper identification of the 3 pins (Gate, Drain, Source). Is this enough to determine if the Mosfet is good? I have no idea.

Next, I used my DMM to try some of the tests I've read about online, including retiredcaps' methods. I get nothing with my meter set on 200ohms. If I set it on continuity/diode test, I get no reading except with the negative on Drain and the positive on Source, and I get a reading of .469

If I try this method with my DMM set on continuity / Diode tester, it does what it says it will on the page. Climbs from 1 to 1.9 and then is either giving me an infinity reading or resetting to 1.

Which of these tests confirms the Mosfet is good? Any of them? How come I don't get and readings with the DMM set on 200ohms?

Cheers,
Alex

[SteveNielsen]

Re: Testing a mosfet with DMM and an ebay smart component tester/ esr meter

Perhaps it is the coil itself.

[Agent24]

Re: Testing a mosfet with DMM and an ebay smart component tester/ esr meter

Is the TV actually faulty? Or does it work fine but with the whine? Sometimes coils do whine under normal operation.

[alessioblaupunkt]

Re: Testing a mosfet with DMM and an ebay smart component tester/ esr meter

Sony procedure to test MOSFET (see attachment).

But do not trust the value: you'll not read 400 ohms to 1kohm.
That's a generic value for some old power mosfet.
I have some BUZ90 and IRFS630 and they give me 1500 Mohm and higher value.
Sometimes the BUZ90 required second or minutes to dissipate the charge applied between G ans S so if I test'em between D and S it gives me infinite resistance.