I've noticed for a while that our broadband at home has been a bit poor. Today I did a speedtest and found I was getting around a third of what I should have, data rate wise. So we did some more testing and were on the cusp of deciding that it was a problem with the line when I remembered that I might have a spare router up in the loft.
Turns out I did. We plugged it in and instantly the speed was restored to something that is very nearly good enough to watch 4K video. In fact we were able to view some of the rather good Harry Bosh series from Amazon in quite sparkly detail.
Oh, and how to fix a broken router? You just need two things. A new router. And a dustbin.