Would anyone be able to help me identify this fuse? The markings on it are: "51NM 250V 1.6A". It is a glass 5x20MM fuse, I am just wondering if it is a fast or slow blow fuse so I can order a replacement.
It appears to be a fast acting fuse: see here
If you can still see the fuse wire inside the glass, and it is a simple wire, it probably was a fast-blow fuse.
I think the great majority of fuses are fast-blow, so itis probably safe to assume that it is (or was :-) ) a fast blow. Using a fast blow in place of a slow blow should be safe, but it may blow with no fault, where a slow-blow wouldn't.