if it is an OLD tube tv, test the tubes and especially the ones labeled Vert-osc, vert-amp etc. If it is a slightly newer tv that has transistors, then check the solder connections on the vertical output transistors. They often become poorly soldered due to heat-stress and vibration and because the factory very often does not solder them sufficiently during manufacturing. Also, the vertical output transistors may be shorted, in which case replacement will fix it. If you have never fooled with a tv... then it is somewhat dangerous because you don't know what the dangers are to take precautions against. It is best to ask for someone knowledgeable to guide you through the repairs so you don't get hurt. The 2 main dangers are getting shocks from charged capacitors even if the set is unplugged and turned off. Also, the picture tube has a danger because the thin neck is easily damaged and could explode due to it has a vacuum inside. Microwave ovens are even MORE dangerous to fool with if you don't know what you are doing. Therefore, you are probably better off just not fooling around with it.