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The EASY Way to check a small SMPS transformer

Vesuvius

Aug 24, 2021
9
Joined
Aug 24, 2021
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I saw a video on YT that showed how to test a small transformer such as a common SMPS transformer using a powered wall wort AC adapter.

I have this transformer......and when I place it on top of an AC adapter it does not respond to the magnetic flux when I connect a VOM, set to AC voltage with (clip on leads) on pins 10 & 11 or on pins 2 & 3 or 4 & 5. Does that mean it is bad? Shouldn't any transformer like this respond to magnetic flux?

In the video his transformer responds nicely and you can determine the Primary from the Secondary sides. His also reveals the turns ratio. It is quite amazing. Mine won't give up ANY secrets. It's like a dead blob.

Thanks
TransformerPins.jpg
 
Last edited:

debe

Oct 15, 2011
276
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Oct 15, 2011
Messages
276
The transformer in the video is not a SMPS type, its a mains type 50/60Hz. That test is no good for a SMPS T/F as they run at a mutch higher frequency.
 

Vesuvius

Aug 24, 2021
9
Joined
Aug 24, 2021
Messages
9
Summary:
The transformer turned out to be fine.

I still do not know of any way to adequately or properly test such a transformer.
I do have an inductance meter and read the inductance from the coils.
However, that information did not provide me with the information I needed to ascertain that the transformer was ok.

What finally make the determination that the transformer was good was that I found that the actual problem in the circuit in question was caused by Mosfets and once corrected the circuit produced it's expected output.
 
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