I picked myself up an old Roland MC303 groovebox but it doesnt have the original PSU.

It runs on 9V DC 500mA center negative 'barrel type' (like standard Boss guitar pedals)

and the SP404 is 9V DC 2A max (not sure about polarity tho.. will check when I get home)

should I take the risk after making sure the polarity is center-neg?
the MC-303 should only draw the current it needs right?

eager to test this MC303 before I can get a PSB-1U adapter for it.

If the replacement power supply for the 303 is going to be psb1u, which is what I read online, than go ahead and use the 404 power supply. Is a psb1u as well. I use my roland mc 307 power supply, also a psb1u, on my sp 404 with no issues for over 3 years.

Awesome. Thanks.

Only reason I bought the MC303 is to test it out thoroughly then pass it on to one of my friends wanting to start down the long hard road of addiction and frustration that is hardware music production. I have more than enough gear already... But I get the feeling that the MC303s awesome arpeggiator will make me think twice about selling it

When I got home I realised that the SP404's PSU is infact a PSB-1U.. blonde moment.

the MC-303 is working well apart from 16 years of grime and abuse (its firmware Ver 1.03 produced in 1997 and the most stable). the main volume knob is broken loose but still works.. sorta.

Have a copy of the service manual and I'm going to crack her open and clean everything individually and try fix the volume knob, maybe replace the pot if necessary.