[R-390] OT: Humbug transformer

[Barry]

I've been working on a low-voltage power supply for a while now and am getting to the final assembly stages.

When I bought the transformer for the project, I noticed it had a bit of 60-cycle vibration (hum).  I wanted to avoid the cabinet from becoming a sounding board for the hum so I isolated the transformer on a series of neoprene cushions (sink washers) to both provide a little shock mouting and to minimize the contact area the transformer mounts make with the cabinet.  The cabinet, by the way, is constructed from solid 3/4" red oak.

Last night was the first time I was able to test the mounted transformer and sadly there's still a considerable amount of hum.  It doesn't appear its a sympathetic vibration carried through the mounts to the cabinet but simply the transformer itself sitting there free to vibrate.

Is there any sage advice to cutting down on the hum?  Perhaps since the cabinet is very solid, I should have gone the other way and clamped it tightly to the cabinet and the cabinet would absorb the vibrations?

I realize it's a long shot and I'm either stuck with the hum or replacing the transformer but just thought I'd ask.

BTW, this is an open-frame style transformer.

Thanks,

Barry - N4BUQ