Trackball will not scroll vertically only laterally.

DENNIS,I have taken the trackball out of it's square housing. YOU MUST BE VERY GENTLE THROUGH-OUT THIS COMPLETE PROCESS. You can get hold of myself at mcmurdojohnston@gmail.com. Taking a medium sized safety pin,and drawing it on your leather belt ,making sure there is no bent tip on the pin point ,as this can damage the ball,or the "pick-ups" inside the housing.Gentley insert the pin between the ball and the soft yellowish circular housing. This must go no deeper than the depth of what you yourself can see on the unit. I use a 40-60 watt light,and hold the complete unit close to bulb. when your fingers get warm, that is enough warmth to make the ring ,Malible enough to pry it back away from the ball. You will not need to go much past the "half-way" mark of the circle.You will see the trackball becoming quite loose,at this point,you may put the pin a little deeper,and VERY GENTLEY LIFT ON YHE BALL. Now you will find quite a bit of lint etc. inside the cradle which holds the ball. I use part of a bamboo chop stick sanded to a point, to clean out,all 4 quadrents,of contacts and in corners. Try to blow into the cradle areas through the "corners" underneath,or outside of the unit,as much less chance of jamming a piece of lint deep inside of the cradle. when finnished, return trackball to it's housing ,and use the bamboo to gently work the soft ring back snug around the ball. "BOB'S YOUR UNCLE"