transformer hum

[kra]

I have built a 48 volt power supply that seems to work ok but it hums and vibrates a lot when I install an enclosure
I have let it run for a couple of hours and everything seems ok
(microwave transformer rewound with #14 magnet wire)
Is there a way to controll this humming an vibration?
(leaving the cover off helps but this holds the cooling fan)
thanks,
Randy

[ViperTX]

That is one of the problems with unpotted (or unimpregnated) transformers. You could try potting it...or just mount it on rubber groumets.

[2muchstuff]

Is the cover made out of steel or aluminum? If steel, the transformer could have a strong enough magnetic field to cause the cover to resonate at 60 hz. Also could be a loose lamination in the core causing noise and the cover amplifies it.

[Al_The_Man]

If it is a square laminated transformer, they usually are dipped and baked in shellac. Another way, if you have a MIG welder is to run a narrow bead across the laminations on either side, this is also a common practice by some manufacturers.
Al

[kra]

thanks for suggestions
the core is welded across already and the housing is sheet steel
also the core is shellacked
i will try an aluminum cover and the rubber spacers
thanks
Randy