Playstation doesn't recognise controllers when plugged in?

Hi. Recently got my Playstation out after it has been sitting in its box untouched for several years (due to PS2 coming along). Everything is working fine except it does not recognise the controllers in either port at all (cursor doesnt even appear on the memory card/music screen). The controllers work fine as I tested them on my PS2. Opened her up and dusted it all off but this has not solved the problem. Could it be a blown fuse or something? I must admit I dont really know what it is i'm looking for. Help would be greatly appreciated!

(yes I have a PS2 and PS3 that work, but thats beside the point! I still play my NES and would love to play my playstation 1 games on my playstation again!)

Regards, Dan.