supajet 101 water doesnt turn off!?

My acient Supajet 101 is well past its sell by date, but it has been such a good unit if its fixable it i would think its worth a try.
The problem is the water doesnt turn off. before that it did some times drip a little, but not always.
Does anyone know what might be at fault and or what the cure might be?
I saw the question of a supajet 101 with no water, the clip on the dial was broken, i will look to see if i can sus if it could be the same problem in reverse.
Any ideas welcome.
regards kris