My slim ps2 isn't reading the disc. what do i do?

my slim ps2 is reading the disc because its just not spinning. it only reads if i hold the lid down with lots of force but when i let go again it can't read it. i found a solution for a while by putting some books on the lid but it gradually needed more and more weight. now it only works if i put 3 kgs on it but i'm scared its going to cause other problems. i've worked out that the lid have a part which pushes down on a on thing in a hole in the ps2 towards the back near the hinge of the lid but i don't know what to do. has anybody else had this problem? and does anybody know how to fix it or what i should do?