I found someone that wanted to sell an Ashdown mag 400 head but i need some advice. First he says it's been broken since he got it. basicly it's in new condition and he's just too lazy to try to fix it. What it does is that it's turns on but when he hooks it up to cabs their is a high pitched sound that comes from it, kinda of like distortion, with and without hooking up a guitar. he says that he called ashdown and he doesn't know about the warranty and he says that it's possible that one of the caps are shot. What should i do? He want's 300 for it.