I just got an SWR SM-900 really cheap but it has a problem when turned on if the top of the amps metal touches the inside (Head sinks) on the top left side of the amp it seems to make a large nasty pop/crackle. It is only when something touches the Heat sinks though. I opened it and tried it and it works perfectly except if the metal block inside is touched or poked. Help me!!! -Vince P.S. i am dumb they are heat sinks not power transformers...stupid teenagers!