Thank you all for your help so far.
I forgot to check this forum for a while and replace a few more parts from spares we got.
I have replaced the driver board for the hopper, the PSU and the MPU.
After replacing the MPU it worked fine for a bit but this is the thing that hit me after checking this thread.
I removed the hopper to put coins in and after rebooting the machine the alarm went off again (which taking out and back again probly made a bad connection on replacement)
So i think you could be right with the hopper not connecting properly.
I will check this tonight and let you know.
Thanks again.