Mate, you haven't paid for it yet have you? Sounds like it either has the mixer section set up with mostly noise and not much else. If not, it could be broken. Where are you buying it from? I don't know about the second hand sales over there but here you have a 30 day return period if it's from a store.
If you can, go back into the place and if possible take a brand new 12v 1amp psu with you just to make sure you have good power. Patch up a simple sound by turning all the oscillators down bar one, say the Square (nice a loud they are). Turn cutoff up full and put the resonance at about 9 o'clock Turn Brute Factor down. Put both volume controls at full bore. Set glide to 0. Place all the LFO dials to 12 o'clock so it's not doing anything to anything. Set the attack to zero and put decay up full and do the same to the sustain and release on both the envelopes. Put the envelope speed to fast. Turn off the arpeggiator. If all is well you should get a nice buzzing square wave sound. If that's good, turn down the square and push up each of the other oscillator sliders in turn to check they are all good also. Also do the same with your headphones plugged into the main output to check it's not affected as well.
Good Luck,
markd.
