My beloved SFX-6 internal power supply has always hummed mechanically, it does not affect the audio output at all and as it has got older it has got worse, I have had it from new as I was a beta tester, so it is well outside of warranty anyway.
The humming has always bothered me, because when monitoring at low levels it becomes very distracting, so I looked into various ways to eliminate it, I tried mains filters but they did not work, I read up on transformers and found that this kind of hum is caused by the laminations of this kind of transformers core vibrating.
To cut a long story short I contacted Elektron and spoke with Olle, he told me that spares were no longer available direct from Elektron but that the transformer part is still available from the manufacturer, I also asked what the rating was and asked about the possibility of using a mk1 sfx60 psu, but again these are no longer in stock, he advised me that a compatible part was made by Mascot in Norway so after a few emails eventually managed to get an external psu with a UK plug from one of Mascots UK stockists, the cost was just over £35.
Anyway fitted it today and all working fine, I made a small plate and removed the IEC socket and internal PSU, I used the internal wiring and switch, and only had to drill 1 3mm hole to fit the plate.
Now my SFX-6 is no longer humming
If anyone is interested I will post some pictures and further details.