I just checked a non contact voltage detector on our ancient series Christmas tree lights.
[They were my wife's family, I'd toss them if it were left to me. I hate series lights!]
Anyway, the string was dead, as expected. The first pass didn't? catch anything. probably because the hot was on the 'cold' side. I reversed the AC plug and the 5th bulb was blown. Easy peasy.
Now if I can just get her to change to LEDs.......
