If you have a loud buzzing/humming noise rather than a scream it's probably a wire off the jack socket which can be easily sorted by removing the two screws on the jack plate and re-soldering the wire. If that's not the problem it could still be a broken wire but under the scatchplate which involves a bit more work, ie removing the strings and the whole scratchplate.
john forster
December 2007
http://www.fender.com/support/diagrams/ Has wiring diagrams for all Strat models