transformer.

[washefuzzy]

My cat's heating pad has a transformer that plugs into an outlet.
This transformer is making a buzzing sound. Is it safe to be using the transformer?
Thanks

[Greatwhite]

That's probably a sign of impending failure.  But it's ok as long as the smoke doesn't get out of it.

It's a little known fact that all electronic equipment runs on smoke.  Once the smoke gets out, the device doesn't work anymore.  I learned this over many years of building/repairing computers.

[bt]

Not just any smoke though.  It's the blue smoke that they need to work!