Repairing LED light strings

[LORisAwesome]

Hi

Last year I bought a bunch of LED strings for my mega tree. I plan to use them on the roof this year.

They are 70 ct strawberry type lights 36 ft long, and are 1/2 wave. I have a number of strings where only half the lights are working. I'd like to repair them, but I don't have a clue how to figure out where the problem is.

Would a light keeper pro be of any use?

Thanks

[-klb-]

LKP is great for incandescent, but keep it away from LED!!! It only takes a few volts to cook a LED, and the LKP puts out a few thousand volts...

[Keith Adams]

As I found out the hard way a couple of years ago on some cheap Lowes mini's. If they are removable leds you could remove them and put them in the spot at the top of the lkp to check the bulb. Try both ways because it will only light in one direction and not the other.

[gizmomkr]

I'm not saying this is the best way, as it has some inherent flaws - but you asked:

This will work to eliminate 1 bad LED. un-bend a paperclip, press it into the bottom of the slot of each bulb- you are basically shorting where the bulb would normally connect. The problem is IF two LED's in the same section are out- its near impossible to tell,so this wont work. I would only "hold" this for a moment, because its raising the voltage of the strand by 1 bulb (2.5 ish volts)

You could apply similar principle to the "string / section" shorting some part of the string with a razor blade into the two wires - it would potentially raise the voltage much higher, and damage the remaining lights though. You also dont want to short to the 3rd wire thats feeding the female outlet at the other end. And you might cut the wire with the blade - So this is REALLY a bad thing to try

You could use the blade to "short" a single socket, if you are carefull, its much quicker than the paper clip method.

I just hate anything that makes me pull bulbs from sockets - In the end ALMOST all the LEDs are mini type connectors and they are hard to pull appart. Would the Razor expose the wire- well we are talking a hair-line slice, chances are not verry much - its a similar idea to the "Bed of Nails" connections on a telco style test set - you would never really see the hole in the wire.

Im not saying they are GREAT ideas - just ideas.

[Guest guest]

LORisAwesome wrote:

Hi

Last year I bought a bunch of LED strings for my mega tree. I plan to use them on the roof this year.

They are 70 ct strawberry type lights 36 ft long, and are 1/2 wave. I have a number of strings where only half the lights are working. I'd like to repair them, but I don't have a clue how to figure out where the problem is.

Would a light keeper pro be of any use?

Thanks

I know this may not be the best method, but this is how I do it. I take ALL the LED's out of the dark part of the string, remove one LED from the working side and then plug each LED in to see if it lights, if I find one that doesn't work, I set it aside in a bag labeled BAD LED's, but I keep going because I found 3 bad LED's in one string once and if I'd have stopped and put them back in, the string part that was out still wouldn't have lit!

Also this way if ALL LED's do work, then if the string has "warts" on them, which are the rectifiers that convert the ~AC~ voltage DC to light the LED's, then I'd say the rectifier is the culprit, no fixing that. If it's like a 70 LED string, and each end has a rectifer, believe it or not, YOU CAN CUT A LED STRING in HALF making a 35 light LED string, but you have to know where to cut the string. I have done this with many 50 and 60 LED strings I have converting them to 25 and 30 LED Strings. Where you'd usually make the cut (on a 70 LED string) is between the 35th LED from each end of the string, that is count 35 LEDs from the male end, count 35 LEDs from the female end, so the cut would be between the 35th LED on each side, same way with 50 or 60 count, just count down 1/2 the number of the string from each end and make the cut. You can either then add a new female plug on the cut string(s). On the offending string that has a bad rectidifer, I cut off either the male or female plug, again, depending on which side of the string the rectifer is bad on, and use the male or female receptacle on the working string.

I use these BAD strings that I made into SHORTER working strings as "splice strings" for areas where a regular sized string wouldn't work or I use them on stand alone decorations like a plastic cutout type of decoration like a Santa Claus, Snowman or anywhere where a smaller string would be of better use.

Good luck on repairing your bad strings, but most often on mine, I have found it's not the LED's, but the rectifiers, so I also mark and keep the good LEDs from the bad side of the string for replacements for the new smaller string I made from it.

Now remember, this cutting of the LED strings ONLY WORKS if THEY HAVE MORE than ONE RECTIFIER on the string. Some of the newer LED strings don't have the big bulky rectiifiers that are visible and may/may not be installed in the plug itself. So don't use this method if there are no rectifiers on the string or only one rectifier or you will blow what's left of the string! Altrhough exploding LED's are somwehat fun, the smell from one that POPS is horrendous! LOL

[Steven]

Most of my LED failures were caused by bad connections between the bulbs and the sockets. That's why I will never again buy an LED string with removable bulbs. The other thing that caused failures was a blown rectifier, but half-wave strings usually don't have rectifiers (because the LEDs themselves are rectifiers).

To find the bad bulb/connection, I used a voltmeter. I unplugged a bulb in the middle and checked for voltage between the socket and neutral. Then, depending on voltage/no voltage, I went for the bulb in the middle of the half that I identified as bad.

[LORisAwesome]

Thanks for all the suggestions.

I tried to remove a light, but, I wasn't able to get it loose. I think the bulbs are not removeable.

I'll try Steven's suggestion. It sounds like a good idea.

Thanks again.

Jerry

[Guest guest]

LORisAwesome wrote:

Thanks for all the suggestions.

I tried to remove a light, but, I wasn't able to get it loose. I think the bulbs are not removeable.

I'll try Steven's suggestion. It sounds like a good idea.

Thanks again.

Jerry

If the LED's are NOT removeable, then no fixing the string without cutrting and splicing another NON-REMOVABLE type LED in it's place. If you do that make sure you get the polarity correct or the string may light, but the backward LED may do one of several things, not light at all, glow very dimly, so dim it's almost impossible to see it unless in a darkened room or it may go KA_POW and explode the LED. The second could also after being on for a while cause the LED that is in backward to POP as well. LED's unlike incandescents have a + and a - side, so if you happen to repair the string with another sealed LED (if you can even buy replacements, I have doubts you can) definitely make sure it gets installed with the polarity correctly set.


This is why I prefer NON-SEALED LED strings, at least if it's only a LED that goes, easy enough to replace and have a full working string again. Sealed strings are just something I stay away from because of the possibility of a LED burning out for some reason and it does happen. Just my opinion and why I prefer replaceable LED's over Sealed ones.

[Max-Paul]

Steven,
Ok, this is just a friendly jest, but how are you "Unplugging" a LED if you refuse to buy any again?

Ok, I dont know for sure where to buy these but many years ago I could access what are called dissecting pins like what you would use while dissecting a frog on a wax pan. These are wooden rods about 1/4" X 4" and small steel rods in the wooden handles with points. We would then take test lead wires and solder them on near the handle and with banana plugs on the other end.

Ok use the half way technic I learned in electronic school. So take one lead and pierce the lead between the male connector and LED (with no wire warts) and take the other lead and pierce the lead between the 35th and 36th LED on a 70 count. If no voltage, go back to the lead between 17th and 18th. If you do have voltage, go between 26th and 27th. Anyway step forward by half or step back by half to try to minimize the punctures. Might want to seal the punctures with liquid electric tape.

WARNING: there will be voltages that you could come across that will kill you. Please be very careful and do not handle both probes at the same time. I highly recommend that you work on a wooden table and keep your body above ground. aka isolated from ground.