Dusted off my soldering iron, brushed up on technique with a couple of Youtube vids (I haven't soldered anything for a loooong time) and had a go at replacing the transistor in my spare (failed) IMRC unit. It seemed to go well, everything looks right, although the proof will be in the fitting - not sure when I'll get to do that, it's a bit bloody chilly outside to be mucking about under the bonnet...