Re: Broken amp question.
How cheap. If it hisses when running, the transformer may be OK. It could be as simple as a bad jack or complicated enough to cost over a hundred to fix. If the price is right, take a chance on it. It could even be a blown tube, and you really get lucky.
Don't fix it while you check it out. Just turn it on, listen, then buy it. If you retube it in front of him, the price could possibly change.