Emax

hello, i'm a new user here and this is my first post.

i had an emax ii for a couple of years, and it had some power 
problems that grew increasingly severe...i ended up deciding to 
buy another. the market for good used keys around here is fairly 
slim, so i decided to ebay it. the guy had a good rating and 
whatnot.

here's my problem: when i load up the banks, i can get just the 
tiniest amount of output from the headphone out (and no other 
output). what little output i do get is very distorted, and there's an 
electrical sounding hum in the background. i've checked to make 
sure i'm on the correct voltage, which i am, and the guy from 
ebay insists that it was working and that this is just a preference 
that i can change. i'm beginning to grow doubtful of both of these, 
but could it possibly have taken a hit that could do this during 
shipping? if not, does anyone know what would cause this?

thank you very much for your time,
chris