A Different Way of Fixing a Christmas 3-wire LED Lights

This is an instruction about fixing Christmas LED lights with the LED Keeper tool – beyond the manual. When the tool didn't seem to work, I dug deeper into LED basics and discovered a workaround that isn't mentioned in the instructions.

1. The LED Keeper which you can get from a home improvement store or Amazon: https://www.amazon.com/LED-Keeper-Light-Repair-Tool/dp/B007H4I8HY/ref=sr_1_3?crid=3HG29CVNU47BG&keywords=fixes+christmas+led&qid=1699825952&sprefix=fixes+christmas+led%2Caps%2C150&sr=8-3

• The picture shows typical 3-wire LEDs, in this case there are two independent groups, left half and right half. When one (or more) LED in a group is bad, the entire half fails.
• When you trace the wires, they are grouped by 3-wire, adjacent groups are separated by 2-wire.
• LED is semiconductor diode device. The electrical current flows one way to light it.
• The top of the 2nd picture shows the electrical from your home receptable, it is a full wave AC 120V (in US).
• The bottom of the 2nd picture shows the electrical current flowing through LED. Because LED only allow current to flow one direction, it only gets half wave.
• Let's say each half has 30 LEDs (total of 60 LEDs). Since they are in series that means each LED get 120V/30 = 4V. Then it is divided by two because it is half wave (50% duty cycle in engineering). In this case effectively 120/30/2 = 2V.

To summarize the original instructions: begin with the first dark LED adjacent to a lit LED (refer to the image). Use the LED Keeper to test it; if it illuminates, proceed to the right to locate the defective LED

The LED Keeper method relies on the assumption that current flows from left to right (see diagram). In my case, the actual current flow was from right to left, which reduced the efficiency of the recommended troubleshooting approach. The way the LED Keeper works is supplying positive voltage to the probing location.

Without knowing which direction of LEDs currents are flowing, I found the best way is to probe from each end:

1. In the picture, it starts from "PROBE 1". If it lights the LED, move the next right LED.
2. If "PROBE 1" above fails, start from the far-right side. If it lights the LED, move to the next left LED.

Why is this method more efficient? It is because step 1 above, if you guess incorrect LED direction, you may be probing one by one all the way to right side. Or you may think the first LED of the step 1 above is bad.

In summary, on a bad half string of LEDs, start from one end. And if it fails, the next thing is to start from the other end.

To fix a bad one, you can follow the LED Keeper instruction, it could be the LED or corroded socket.

For a corroded socket alternatively, you could cut the socket wires off and short/tie the wires together. In this case the voltage of each LED will be higher therefore brighter. Do not short too many, you will burn the LEDs because the voltage on each LED may go too high. A little brighter LED may survive better in a colder climate.

Instead of probing each end, another starting point is finding the direction of the electric current. The picture shows the LED bulb tester, (+) and (-). The current from from (+) to (-). The first LED to probe is the end with (+) sign. The LED Keeper applies positive voltage to the (+) side of the LED. That should be the starting point.