I have an old Roland mixer, the M240. I've had it for years, ever since some idiot screwed me over when i bought it, promising to send me the power supply but never doing so. I did a little research of the internals here: http://atosynth.blogspot.com/2013/07/roland-m-240-power-supply.html
Today I finally googled a bit about it again, and found two interesting posts made about a year after mine:
https://djjondent.blogspot.com/2014/10/roland-m-240-mixer-power-supply.html
https://djjondent.blogspot.com/2014/11/roland-mixer-power-supply-replacement.html
Basically it says that the PSU is a simple centre tapped transformer with a diode rectifier and two caps. From Jon's posts it is clear that at least the Boss PSU he uses has two large filter caps in it - it's hard to read the ratings - 35V is clear but is it 220uF or 2200uF? In any case there are two 2200uF caps in the M240 so anything (or nothing?) would be fine I guess.
Jon uses the Boss ACE-120 but that is not the original PSU for the mixer and it is 300mA, not 500mA. I couldn't find an ACE-240 anywere either, so I had a look in the owner's manual for the M240. It says the following:
Aha, so for my 240V mixer I need the ACC-240A or E, not sure what the difference is - and it is rated at 32VA
It would be quite easy to build a power supply, but I will still have to find a matching plug and THAT won't be easy.
