'Repaired' subwoofer hums from TX

[scottb721]

I was given a huge Accusound HD Series 1 subwoofer that was dead. I opened it up and found a couple of bulging 6800uf caps. They were part of four so I replaced all four.
Subwoofer now works great and I might actually swap it for my Martin Logan, however, when you're within a few feet and there's no input playing you can hear the transformer humming (driver is silent).
Probably speaking nonsense here but I measured the 'noise' and it's peak was 150hz with harmonics 50hz either side.

Anything I should try to fix the hum before just sticking it on a smart switch so it turns off when not needed ?

Thanks