[Major Tom]

Right, the four screws on top release the chassis, it should then slide out the back.

It could be the jack itself is actually broken, in which case you'll need to replace it. What I have seen in PC board amps is usually the jack is ok, but its solder connections on the underneath of the PC board are broken and it only needs to be re-soldered. Often the "break" is hard to see, its a hairline circular crack.

BTW, the way to avoid this in the future - always, always strain relieve the cord; wrap it around the amp handle, so when it gets tripped over or yanked on, it doesn't pull on the jack itself.

[+SEAL+]

Okay. I was just a little nervous, because I could tell that the screws went right into the wood. I didn't want to strip the threads out of the wood.

Thanks for the tip! I hadn't heard about doing that before.

EDIT: Okay, I've taken the screws out, but the chassis isn't being very cooperative. It's slid only about a sixteenth of an inch or something like that.

EDIT: The chassis came out!
Here's a pic of the socket. I'm trying to figure out what to do now.