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PlanetChristmas Magazine July 2012

To find the bad LED, make sure the light string is unplugged from the power source and now power up your LED string tester. Attach the first test clip at one end of the dark sec- tion of lights at the wire entering the first LED. Attach the second test clip to the wire exiting that LED. With any luck the light will come on and you’ve proven the tester is working. Since the voltage of the tester is AC (alternating cur- rent) we don’t have to worry about polarity. Now disconnect the second clip, go out about five lights in the series and reconnect the clip to the wire leaving the fifth LED. If all five lights come on, move to the next section. If the lights don’t come on, move the second light clip to the wire leaving the forth light. If the lights come on, you know the fifth light is bad. See how the What happens when you short the test clips process works? Light several bulbs in a series, if together? Bad things. Don’t short the clips. they work, move on to the next. If the bunch doesn’t light, work backwards to isolate the bad LED. the lights are in series and you’ve wired around Your LED string tester will power 8-10 the break. Doing this means all the other lights LEDs just fine. As you develop your own tech- in the series receive a little more voltage but nique, you’ll figure out how many lights make they’ll work fine. sense in the initial test. We’ve found five lights are pretty easy to work with but we know others Portable LED String Tester that will initially try testing 15 and work back if If you need a field tester, you can replace the there’s a problem. transformer with two nine volt batteries wired in series. The testing technique is the same but We said this was an LED the test clips to each side of the first light andnow you need to worry about polarity. Attach string tester. if it doesn’t come on, reverse the clips, mean- Not an LED string fixer. When the light comes on, start moving out thating you’re reversing the polarity to the LED. second clip and test just like before. You can get really clever and add a DPDT (double pole Find a bad LED? Now what? double throw) toggle switch to the unit to eas- We said this was an LED string tester. Not ily reverse the polarity of the clips to speed the an LED string fixer. If you have a sacrificial initial testing. light string to use as spare parts, you can cut out the bad LED and splice in a new one from Final Tips? the sacrificial string (making sure the polar- Most bad strings can be brought back to life ity is correct) but this is a timely process. Most in five to ten minutes and is well worth the people cut out the bad LED, solder the exposed effort. You’ll come to a point when you realize if wires together, add a little heat shrink tubing to a string isn’t working after 15 minutes, it’s time make the connection weatherproof and declare to scrap it and move on. Now is the perfect time the string functional again. This works because of year to tackle that pile of bad strings. July 2012 | PlanetChristmas 31


PlanetChristmas Magazine July 2012
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