LED Christmas lights have a series lump, what is it for?

Dunno. There are a bunch of LED wiring schemes: The diode or resistor might be hidden inside the AC plug. Or, the LED might have an internal current limiter (which I doubt because these types of LED's are expensive).

Or, the lump might be a flicker suppressor:

When you're done solving the LED problem, could you work in this one? The local squirrels would take a few bites out of the incandescent wiring. I could easily fix that every year. Now, they trash the LED lamps in a manner that is not easily repairable. I end up replacing the entire string each year.

RFI suppressor ferrite cylinder?

LED xmas lights with their long wires and smps are one of the best ways of corrupting wifi connections.

I really doubt that cheap communist chinese manufacturing would go to that expense...

Jeff Lieberman,

The wiring web site was interesting in how poorly it was done, but didn't really give me any answers to my questions.

Well, I indicated that I didn't have an easy answer. Basically, I would need to know what's inside the lump before making yet another guess(tm). It could be anything (diode, capacitor, ferrite bead, resistor, etc). The same components could also be molded into the power plug. Also, unless the series current limiter is in the plug or in the LED's, I don't see how it could be done without something inside the lump.

I am sure there is nothing in the power plug, I have taken apart several of both types of LED light strings, and there is nothing in the plug except f or fuses. I am guessing that maybe the internal diode resistance is enough to limit the current when there are enough bulbs to almost reach 120V just using the internal diode drops. I will have to count how many bulbs are in series in each of the two types of lights and see if that shows any patter n

I rebuild old Christmas light (filament and LED) sets that are given to our local recycle center and then donate the lights to local charities that ha ve resale facilities, and I have several strings of each type in my rebuild boxes so that is mostly a matter of getting to it. I'll post the results after I have done my research.

I took apart five individual LED Christmas light bulbs, from a string of li ghts that did not have a "glob" in series with the bulbs. Each of the light s had a really tiny resistor in series with the bulbs. The stripes and body color on the resistors were so small I could not tell which was the body a nd which were the stripes. My cheap HF multimeter said the actual resistor s were 260 ohms. I didn't try to clip lead the bulbs into a working string of lights so I wasn't able to measure the forward drop across the LED diod e itself. I will try that later this week when I work on some more LED lig ht strings. Right now my repair shop is working on filament light strings.