Vortex Sound Research

I've spotted a good deal on a Dm12 which is a synth I've always wanted to try but the person selling says it has a hiss in the background, like there's "a ground issue". Appreciate its a bit difficult to say without examining it but wondered if anyone come across a problem like this with their own one?

Can't find anything on Google so was wondering if this is a common problem that is likely to be solvable or whether it's a sign of a significant issue? It's still a fair chunk of money so don't want to buy something that's dying...