Static sound from 4 port system

As I posted before I bought a 4 port system.  It does power up and there is picture which looks about right.  I do, however, hear a lot of static sound.  What could cause this?  I did notice that the plug is not the screw in kind and just pushes onto the vcr and the contacts are not the bright color you'd like them to be, they look a little corroded, not sure if that's the problem.  So, the real question is, how to fix this?  The system works and I would like to be able to use it whenever I want to use a 4 port instead of my 2 port.

Thanks