if you are not very very careful you could have already bricked the synthesizer with the wrong power supply. if the box doesn't have a protection diode you are very likely screwed my suggestion is for you o try and get ahold of a ham you trust that does a lot of home-brew or other repair work and talk other.  they could open up the case and find out exactly what polarity the synth is looking for, anyone  who is sighted and is familiar with electronics should be able to find out  weather it wants positive or negative tip.
On Oct 30, 2012, at 7:07 AM, Howard Kaufman <[log in to unmask]> wrote:

> Every other twelve volt supply I have tried doesn't work, no matter what the 
> polarity is.  Very odd!