Originally Posted by: RickBlacker... How? How can a jack be the problem? They don't do anything. No moving parts. I looked closely at the jack, nothing was touching that I could tell which might cause some kind of grounding issue...

The integrity of the signal from the guitar to the amp input depends on having a good elctrical connection between the jack and the cable plug.

The contact that mates with the groove just behind the tip of the plug needs to have enough tension on it to press firmly against the plug. Sometimes the metal of the contact leaf 'gets tired' and doesn't frimly contact the plug. The result is a lot of scratchy noise from tiny arcs between the plug and the jack.