Test Circuit Helps Find the Bad Bulbs in Light String

The holidays are just around the corner, which means it”s time to find out how many light strings survived 11 months in the attic. When we find a clunker, the quest for the bad bulbs usually leads to some really creative expletives at my house.

Thank goodness Santa brought a gift early this year -- the chaps over at EDN magazine published a nifty circuit that lets you find the culprit in both series-string and alternating-series-string lights before you drive yourself crazy. Or Christmas is ruined. Here's another bum light test circuit, with instructions helpfully translated from Dutch. After you've found the bad bulbs, good luck finding replacements for them. This year, my husband wound up buying new light strings after striking out at several stores. Maybe it's a conspiracy!


One comment

  1. Or even simpler… Use one of the FET/LED test
    screwdrivers, move it along the string (no need to make contact), when the LED goes out yo have found the faulty lamp.

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