Can't flash a mag like a dynamo Padsta! So don't shove a battery across it or anything - that would be a very bad plan!
Best thing to start with is the points. They may have oxidisation on them - even if they look quite clean. Get them off and sparkling clean and set them to 12-14 thou. Then check the HT pick-ups, brushes and leads to make sure they seem OK. With them off you can clean the slipring through one of the holes with a bit of non-fluffy rag or cotton bud sort of thing and a drop of some cleaning agent. 5 years is a long time doing nothing, so some parts might well have deteriorated. And it may have been undisturbed for many more years than that I guess . . . . If you're lucky, a good clean up with bring it back to life; if you're not, you'll have to dig further unfortunately. Good luck!
