I recently bought a used Line 6 DT50 head and recently it blew a fuse. I replaced it and immediately it blew the new fuse once it was powered on. I had a an extra fuse and once again it blew. What really should I do? Or what is the problem? I really like this head and spendimg $200 to have a guy look at it seems pretty steep after just buying this head not that long ago. Before all of this it functioned well and fabulous.