Hi-Ho SilvaAfter 35 years service my Silva orienteering compass has stopped working. I didn’t think that they could but mine seems to have lost its magnetism so it will point any way I care to put it. Actually that is not quite true, there is a little charge in it so it will slowly drift around—to point exactly the wrong way! I can only imagine that it has become de-gaussed by an electric field or perhaps from getting too hot but I don’t know how. I trust that airport X-ray machines don’t harm them?
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It would be interesting to see if you can re-magnetise it with a strong magnet. I know you can get hold of Neodymium magnets pretty cheap (probably for a lot less than a new compass) that have an amazing strength. Just be careful not to put it too near anything electronic 😉
Yes, I have some super powerful ones out of a disk drive that I must try and detach from a filing cabinet. How do you think I can hold the needle still so that it is magnetised the right way though? It floats freely in a liquid bath. I will experiment, in the mean time I have bought a new one at half price on eBay.
Not sure how you can hold it in place, my Physics is a little rusty but if you put the magnet near one end of the needle would the magnetism hold it in place? You just need to make sure you get the poles oriented correctly, otherwise it will end up perpetually pointing South!
Another source of a strong magnet, if you need one would be out the back of and old speaker cone. Although I am not sure how well this would work as it is cylindrical.