Testing N P channel mosfets in a Samsung 710N

[robcar]

Hello,

I wonder if it is possible to test in circuit these 4501GM (or similar N P mosfets) found in a Samsung 710N's power board.
I looked in a guide here in the forum, but it is mentioned to measure Ohms and I don't get meaningful data.
So can someone tell me where I should put the leads of my multimeter and the value that I should get in the various testings?

thank you
rob

[robcar]

Re: Testing N P channel mosfets in a Samsung 710N

Ok,
I managed to test a working video, same model, same board, exact revision. Those below are the value that I read on the DMM display in diode test mode, with the mosfets in circuit.

This should be the N-channel side:
Black lead on S1 - red on G1: 0L
Black lead on S1 - red on D1: 0L

This should be the P-channel side:
Red lead on S2 - black on G2: 0L
Red lead on S2 - black on D2: 0L

While with the not working board I got:

This should be the N-channel side:
Black lead on S1 - red on G1: 0.323v
Black lead on S1 - red on D1: 0.004v

This should be the P-channel side:
Red lead on S2 - black on G2: 0L
Red lead on S2 - black on D2: rising till almost 1V then 0L

So, I got 2 different sets of reading, but I cannot tell if they alone can tell me if the mosfets on the not working board are broken, without previously removing them.

[jiroy]

Re: Testing N P channel mosfets in a Samsung 710N

Testing Mosfets on boards isn't what one should do , unless he has a schematic showing what precise voltages should be . Further , Some points or what we call Tip is to be measured with an Oscilloscope .
So basically , if you don't have a schematic , you should remove a mosfet in order to test it in a good way .

[robcar]

Re: Testing N P channel mosfets in a Samsung 710N

Ok,
I'll remove and test the mosfets. Btw I ordered a bunch of mosfets for another very similar display:
https://cdn.badcaps-static.com/pdfs/...dfffdeffe2.pdf
To me they appear equivalent to the 4501GM of this video.

[jiroy]

Re: Testing N P channel mosfets in a Samsung 710N

Ok,
I'll remove and test the mosfets. Btw I ordered a bunch of mosfets for another very similar display:
https://cdn.badcaps-static.com/pdfs/...dfffdeffe2.pdf
To me they appear equivalent to the 4501GM of this video.

All i can help you with when testing the Mosfets is basically looking for shorts , at Diode level . In most cases , if a Mosfet is damaged , you'll see lot of shorts .. While doing this , pay attention not to use your fingers touching the legs cause mosfets tend to change their internal resistance ..

About compatibility , i always prefer the same original type , but in rare cases , when a component is unavailable , you can try if legs of both mosfets fit the right places and the specifics are very close ..