Bob writes:

“I am retired and come into OO model railways late , learning as I go . I saw a post showing how to wire LED’s on a 3v system doing away with need for resisters etc . All went well and has been working great, until now. One circuit with street lighting on has gone out apart from 1st light on circuit. I thought maybe the second light had blown, but tested it with battery and its fine ,I have also checked the feed to 2nd light but my tester shows power there. Is there a simple way to test circuit without disconnecting every light and starting again. Any tips would be welcome”

Add your thought below if you can advise Bob.