Thanks to all of you. Sorry I was a bit vague. The loco has been working well up to now, apart from, occasional 'jerky' movements in the past, due to dirty track, I believe. The voltage is there whether the loco is on or off the track. I have tested in 4 or 5 random locations, but not all round. It wasn't traversing a point, and I wasn't operating one (they are manual at present). Yes, it is clip connection (Peco and mostly Peco Settrack). I was intending to solder later, but I will try it as suggested. The only thing I wondered - time for a confession here - is whether the cleaning might have had an adverse effect. I went right round the track as there was dust etc from the building thus far and, because I had run out of proper track cleaner, used lighter fluid - a tip I was given when visiting a professional layout sine time ago, probably an analogue layout I guess. I have spotted some other posts about what to clean with, and now wonder whether there is sufficient oil in lighter fluid to cause a problem. I am not an electrical expert, knowing just about enought to set the railway up