Sizzling Transformer!

[psteichen]

I'm concerned about the 12V power supply for my under cabinet lighting. It emits a constant sizzling noise from the transformer. All the other components look fine, and it creates a steady supply of 12V from 110V AC. Is this a common failure condition? I can't imagine that the noise is electrical arcing, as it's been doing it for a week. Wouldn't arcing have burned through the wires by now?

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[hermit]

Does it pass the smell test?  Really.  I'm more used to microwave transformers failing but the oder is pretty distinctive.  If the windings are shorting you'd probably catch a whiff of it.  Burnt is burnt. 

[psteichen]

Does it pass the smell test?  Really.  I'm more used to microwave transformers failing but the oder is pretty distinctive.  If the windings are shorting you'd probably catch a whiff of it.  Burnt is burnt.

No, no burning smell at all.

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[psteichen]

This is link to an audio file I recorded with my phone: https://www.dropbox.com/s/1so7w9tkqs181un/Sizzle.m4a?dl=0

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[peteb2]

I can't get to the Dropbox audio sound bite but what happens if you remove any load, does that quieten it at all? I am assuming its a laminated unit and that as a core it will be fairly large to give it the VA spec to allow (halogen.. another assumption) to run off of it. This mass of iron may well be for now assisting in dissipating the heat in the primary that's going on in a shorted turn on a layer close to the inner iron core...

Any hour soon expect the spitting goo to ooze out and the smell if that's the case....

Other tiny thought is is it possible there's something like Ripple Control signal (used to turn water heater systems on/off) being sent on your Mains and and it just happens the transformer has a mechanical issue and is resonating while also giving a slight characteristic hum....

The final thought is it really a transformer because i have found some manufacturers label their units as such: lighting-transformer, but theirs infact a switch-mode module internally ...



 

[Gyro]

The final thought is it really a transformer because i have found some manufacturers label their units as such: lighting-transformer, but theirs infact a switch-mode module internally ...

That sounds like a distinct possibility. Weight and size would be a strong clue, as would having an input voltage range wider than 10%.  Posting a picture should help resolve the question.

[mzacharias]

If it's still working and makes that noise - I would suggest a bad capacitor; maybe a couple. Don't keep using it. Fix it or replace it.

[psteichen]

The large yellow transformer is the one in question. So a bad cap might cause the transformer to crackle? That would be great, because I've already checked, and the part number on the transformer isn't available anywhere. Caps I can do, I've already examined them all physically, and none have any deformities, but I may have to test them.

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[tecman]

Some SMPS designs use variable frequency and often you will hear a hissing, sputtering, crackling and sputtering sound.  Ferrite cores, like on your transformer, have some magnetostrictive properties, which means that they can create an audio output depending on the operating conditions.  Likely this is what you are hearing and had no ill effect, except annoyance.  The only other possibility is that there is a short in a winding and it is arcing while running.  Possible but usually these winding faults result in overheating and as mentioned a burning smell.

paul