I recently ordered a custom transformer and under load with half of its rated current it heats up to 55 °C, and now it's started to radiate a "weez" noise.
Is this normal? How hot is too hot for a transformer?
How can I get rid of the noise? Pushing it down doesn't help!
Update: the iron core was loose (or wasn't tight enough), I returned the transformer to be fixed with a new core.