Is there a way to troubleshoot/fix these LED rope lights?

[Flyover]

I bought these LED rope lights and they do not work. (They were a discounted item and are not eligible for return.) The lights came with a fuse near the plug, plus a spare. I tried both, no dice.



As you can see in the background in that picture the cable has a large choke/ferrite bead...do those ever cause problems?

I guess one option would be to take the thing to a store that carries this item and actually test it out with another plug section (the plug section connects to the lights at the connection you see on the far left of the picture). Before that, are there any other tests I can do at home? I have a multimeter but don't really know how to use it.

 

[oldognewtrick]

I have several strands of those that we use when we go camping to make a perimeter around the campsite. Make sure you have the plug in the correct orientation. There should be 2 pins in the plug that are slightly offset.

 

[Flyover]

Yes, the plug is correctly oriented. There's actually a flat side that fits in only one way to the light so it can't be plugged in backwards.

 

[Eddie_T]

You might use your multimeter to check the fuses for continuity if you can't see if the fuse strip is blown. Also you might check the plug section for DC voltage if the fuse is good. Since we don't know the DC voltage start with a higher scale, my guess is that the voltage is probably 24, 18 or 12 volts.

 

[Flyover]

I have no idea how to use a multimeter. I have one I got free-with-purchase at Harbor Freight (this one) thinking it might come in handy one day. (Maybe today!) Can you walk me through what to do?

 

[Eddie_T]

That's a nice little meter.

Connect the black test lead in the bottom (Com) jack and the red in the VΩmA jack.

To test the fuses turn the dial to Ω 200, turn the meter on and hold the fuse across the probes. If the fuse is good you should see a number near 0.

To test for voltage turn the dial to DCV 200, turn meter on and touch the probes to the sockets in the plug-in portion (with it plugged into an outlet) and it should read 12, 18 or 20V. If it's less than 20V you can turn the dial to 20. Yo may have to reverse the leads to get a reading as we don't know the polarity of the DC voltage.

I you are using the meter on AC voltages you just use the ACV scale and start with the 750V setting.

The CAUTIONS are don't change the dial with probes connected to a voltage and never use the DCA or Ω position when voltage is present. You may never need to test amps.

The meter will also come in handy for testing batteries, just watch the polarity.

 

[Flyover]

Awesome, that's the most helpful thing I've read all week!

 

[ekrig]

Eddie_T beat me to it and gave you a very good walk-through.

Maybe I can add you a few more hints:
- The number that you set on the multi-meter (for AC/DC voltage, resistance Ω, etc.) is the *maximum* that you expect. If it is higher, then the internal protections will cut it off and you won't get a reading. That's why, unless you a decent idea of what to expect, you start at the highest. Then, lowering to the immediate value above gives you precision, as it will start to give you decimal places and so on.
- Generally speaking, the polarity of the probes on the DC voltages isn't critical. If you have the polarity reversed, the multi-meter should just give you the voltage as a negative value.
- For that multi-meter specifically, which I also own, I have yet to get the current (DCA) section to work for me. But you may have better luck than me. Note also that current readings need to use the multi-meter *in series* with the circuit rather than *in parallel* (i.e., the way you measure voltage).

 

[Flyover]

Thanks @ekrig, that's very good to know.

current readings need to use the multi-meter *in series* with the circuit rather than *in parallel* (i.e., the way you measure voltage).

Thanks for that info but I have no idea what it means or how it affects the way I'd measure something. I learned about "series" and "parallel" in elementary school when we'd hook a battery up to a small circuit with a couple light bulbs at the other end, but I'm not clear on how it applies to this.

 

[ekrig]

https://www.wikihow.com/Read-a-MultimeterPlease take a look at sections 4 and 5 in Part 3 of the above page for an explanation on the series vs parallel measurements.

 

[Flyover]

Oh, got it. That was simpler than I thought. How would I non-destructively do this with my lights?

 

[Eddie_T]

Basically just remember Ω scale only with no power applied and don't use DCA.

I have only used DCA once in the last 10-15 years.

 

[ekrig]

Actually, my note about current measuring (and the fact it needs to be done in series) was only as a general tip on how to use the multi-meter; not that it applies to your current problem. Apologies if I ended up creating confusion.

Here's how I would approach your lights problem:
1. It seems that there is a connector between the cord (i.e., the part with the plug, in white) and the LED light rope part. If that's the case, disconnect the two parts and connect the cord to an outlet. *Very carefully* to avoid creating a short, set the meter to 200 VAC, and measure the voltage on the connector at the other end of the cord. If you measure a voltage (say ~110-115 VAC), then you have power reaching that point and the problem must lie in the rope lights. The voltage might be smaller, depending on whether the "bulge" on the cord contains any kind of electronics. Also, if you get no AC voltage, or really small, try measuring with the 200 VDC setting on the meter because there might electronics to "rectify" (loosely speaking, convert AC to DC) the voltage.
2. If you get no voltage, unplug the cord, and, using the 200 Ω setting in the multi-meter, put the probes across the fuses. The meter should show something close to zero. If it doesn't your fuses are busted and you'll need new ones. Otherwise, something is wrong with the stuff in the cord. Depending on whether any electronics are involved, you can try to splice the thing and add a new cord to replace a bad part, but if there are any electronics in the thing, the cord if toast. Maybe buy another set with a good cord and connect the rope lights part directly...? (If you decide to do that, remember to take the light part and test the whole thing in-store!)
3. If there is voltage on the connector, then the problem is with the lights. Visually inspect the rope part to see if there are any kinks or bend that could have broken/de-soldered the LED inside. You can also connect all the part together and plug to an outlet. Since these are designed to be linked together the connector at the end of the rope should have voltage, and if it doesn't, clearly something is broken in between.

Hard to be more more specific without access to the real thing... Hope it helps.

 

[Flyover]

This is great, thanks!

 

[pjones]

There is typically two fuses on those plugs but in your picture I only see one?

I would bet that ferrite you are talking about is probably actually your resistor that drops down the current to the LEDs

I don’t have any experience with rope light so I can’t add much to this in detail, but with my experience with Christmas lights I can say the issue is usually not with the resistor unless they use a capacitor and diode circuit to help smooth out the waveform. If they stuck that circuit inside that blob instead of just a resistor then it could be art of the problem. No good way to test without smashing it open as far as I know... not what I would recommend.

I would bet you have a broken wire somewhere within the strand that you may be able to test using continuity on your multimeter, unless there is actually a missing fuse.

 

[Flyover]

There were two fuses, but it looked like one was a backup. I popped it out to test it, then it dropped somewhere on my garage floor and I haven't looked for it yet (have a pretty good idea where it landed)..

 

[Eddie_T]

I confess I know nothing about rope lights but my curiosity has been piqued so I have tried to read up on them in case I meet them again. Google is not my friend, as I type I forget that (like the NSA) google is looking for key words and showing hits for those words not the sentences.

What I think based upon my findings is that you have a 120v 2 wire LED rope light. The power cord contains fuses and probably a rectifier (my 12, 18 or 20v comment does not apply). The rope probably has cut lines at measured intervals and the LEDs within the cut lines are arranged in series (and maybe with resistors) to reduce the current.

This means that the voltage at the end of the power cord may or may not be 120v depending on whether the rectifier is full or half wave. It will be DC thus the polarized plug but not smoothed so may read on either DCV or ACV scale.

There is another test point by removing the cap at the end of the rope. With voltage applied the same voltage should be present at the end of the rope as was measured at end of power cord.

With the rope unplugged from the power cord the Ω scale can be used to check for a broken wire. Place a probe on each plug prong (one at a time) and check the wires at the other end of the rope. One of the wires should show close to 0 ohms, repeat with other plug prong. Checking for a shorted wire may not be as simple as all the circuitry in the rope may yield a reading close to 0 but you could test the ohms between rope connector prongs to see what the meter reads.

 

[pjones]

I confess I know nothing about rope lights but my curiosity has been piqued so I have tried to read up on them in case I meet them again. Google is not my friend, as I type I forget that (like the NSA) google is looking for key words and showing hits for those words not the sentences.

What I think based upon my findings is that you have a 120v 2 wire LED rope light. The power cord contains fuses and probably a rectifier (my 12, 18 or 20v comment does not apply). The rope probably has cut lines at measured intervals and the LEDs within the cut lines are arranged in series (and maybe with resistors) to reduce the current.

This means that the voltage at the end of the power cord may or may not be 120v depending on whether the rectifier is full or half wave. It will be DC thus the polarized plug but not smoothed so may read on either DCV or ACV scale.

There is another test point by removing the cap at the end of the rope. With voltage applied the same voltage should be present at the end of the rope as was measured at end of power cord.

With the rope unplugged from the power cord the Ω scale can be used to check for a broken wire. Place a probe on each plug prong (one at a time) and check the wires at the other end of the rope. One of the wires should show close to 0 ohms, repeat with other plug prong. Checking for a shorted wire may not be as simple as all the circuitry in the rope may yield a reading close to 0 but you could test the ohms between rope connector prongs to see what the meter reads.

This sounds very similar to how LED Christmas lights are constructed. I do have a good amount of experience with those lights.

The reason there are three wires that travel the length of the strand on a Christmas lights is because they extend the hot wire through to the end plug so the next string that gets plugged in has full voltage. Testing from plug end to the other plug end will not test the lights, just the continuity of the traveler that goes from end to end.

The Christmas lights swap phase polarity half way through the strand which is why they momentarily change to a two wire strand in the middle of the string. To reduce the numbers of resistors and the cost of manufacturing, those two polarities share one resistor each, wired in series (not all but most strings on the market do this). If one light fails on that polarity then they all go dark, but the other polarity continues to shine because it is wired in parallel to the other polarity.

If the similarity is correct between the two types of light strings, and If the rope light is new, then it’s possible but unlikely that both polarities would be failed causing the whole string to go dead.

Since the fuse is missing checking plug end to plug end would be a good idea just to see if that fuse is required. If the fuse is missing then you won’t get continuity between the two ends. Check both wires separately. You May only have 1 fuse if the plug end is polarized.

 

[Flyover]

I'm between things and have to run, but just to clarify, although there were two fuses stored in the plug, one (the one that's somewhere on the floor of my garage right now) was clearly just being stored there as a backup; it sat in a cavity in the plastic -- the cavity had no metal connections. The other one (still present in the plug) is in a cavity that has metal connections.

 

[Eddie_T]

I hope I am not giving too many thoughts but here's another one. Since the power cord is removable it can be checked separately and since your rope is a 2 wire rope if it fails the end to end continuity tests you may be able to visually (with a backlight) find which section has a broken wire.

By section I mean between cut lines assuming your rope has cut lines. A section is where the rope has the proper number of LEDs in series for 120v. A bad section could be removed or repaired if you can visually see a broken wire. The picture is a schematic of one section which is probable about one meter long. You should be able to easily see the two wires

If it weren't for COVID I would drop into Lowes and take at look at your product and offer clearer instructions.