rattling noise from inside when I switch on.

When I turn switch on to use planer there is a rattling noise like something is loose coming from inside. I removed the vacuum port and cover but didn't see anything loose. Was going to remove the switch cover to look inside there so I removed the top screw of the cover and need to know where the bottom screws are because the switch comes out at the top but is hung up at the bottom. Didn't want to try to much because I don't was to damage it. The planer works great and cuts really well just don't want to keep using it in case something got inside of it. I purchased this unit used.