[Heady]

Bought a 20-0-20 200VA transformer from Farnell (not a toroid). Bought it for a power amp (amp5 from 41Hz) which I am building. I have tested the transformer for its output voltage and for checking the amp's power supply.

Today the transformer started humming when I turned it on. Is it faulty? Any expert can please comment? Do I have a case to return it to Farnell?

Thanks.

 

[Garbz]

From PSAudio: "The short and simple answer is that transformers hum because of an effect known as 'lamination rattle' caused by DC voltage on the line or poor construction or both. 'Lam' rattle occurs in all transformers to some degree, that degree being related to the quality of the transformer and the quality of the line voltage."

I tend to find that higher power transformers exhibit this far more than small power transformers. This is one of the reasons I favour torroids for poweramps. I have no idea how to get rid of it, but it is unlikely to be faulty so I doubt you could return it. Someone else may know more.

 

[Voodoochile]

41Hz? Is that the norm in SG?
I'm not sure how a transformer reacts to that if it was designed for 50/60Hz, or 60Hz. Being Farnell, I'd guess it was 50/60Hz.

As Garbz said, it's not all that uncommon, and bigger units tend to be more challenging to assemble really tightly unless you spend some big bucks.

If there are through-bolts, you could try tightening them. If not, perhaps another soak in varnish might help a bit. But probably not that much, if it's really getting noisy.

 

[n_maher]

Quote:

Originally Posted by Voodoochile 41Hz? Is that the norm in SG?

I'm pretty sure that he's talking about this 41hz.

 

[Voodoochile]

Well shat, I feel stoopid now!

Carry on.

 

[n_maher]

That may very well be the only time I ever get to correct you on something transformer related, Mark.