Weird issue with 200 count LED string and LED keeper results

[XmasinVancouver]

I have a 200 count LED string of c6 bulbs. I've spent some time researching and looking up schematics, guides and more to make sure I wasn't mixing anything up. I do understand the concept that a string like this is probably 4x 50 led strings wired in series. So having a random section out isn't that rare or baffling why the section before and after it works. I know that a section in series will all be out if there's a failed led, socket etc. I've used the LED keeper in the past to help diagnose and narrow down issues like this and to test bulbs and sockets (and used their pods when a socket is no good). This season, I reviewed all their instructions, video guides and other information I could find before getting to this point. There's a few weird findings that are really throwing me off though or confusing my understanding of what I thought, and I can't seem to find anything specific as to if this is normal or answers from others posting this. So here's what I'm seeing:

- 4 sets/sections of 50 led's in one string. Section 1 will be closest to the blade plug and section 4 furthest from it and terminating in the female socket.

-Section 1, 3 and 4 all illuminate, section 2 is unlit when powered from A/C.

-Using the led keeper and it's steps on section 2 (mark start and end of non working section, select wire coming in or out of a bulb roughly halfway through the non working section and pull the trigger. One side of the bulbs to either side of that test point should light up, move your marker from the working side to the test point to now narrow it down in half to the problem area. Keep repeating until you find bulb(s) that won't light no matter which side of the wire you tap into). Have done this process probably 5 times already with the led keeper, and everytime, every light in section 2 ends up lighting up with the led keeper. But back to wall power, nothing from section 2. There's no current control or resistors or other "canisters" on the string. By these findings, I should conclude that:
-All the bulbs are working
-All the sockets are working
-The current is able to flow from the blades to section 2 (if there was a break between power source and start of section 2, LED keeper wouldn't be able to power those LED's or complete that circuit)


-I should note an oddity that may or may not be related. The very first LED after the power connection in section 1 doesn't work when powered from A/C? And yet, everything else (other than the above section 2) works fine with this first LED not working (What happened to the whole "if one failure, the rest won't work in that series"?). Weirdly, that bulb tests perfectly in the led keeper test socket. If I pull that bulb that doesn't light up when it's on A/C, none of the string works (which is what I kinda expected). But when I put it back in, the whole string lights again despite that first LED still not turning on. Here's the kicker again: the wiring to that first led is one wire going directly from the plug to the socket, and 2 wires coming out of the socket to go downstream. Using led keeper on that first wire between the wall plug and the first LED doesn't do anything, but using it on one of the 2 wires that exit the LED socket it lights up fine!? If I go down the line a few bulbs let's say 3 bulbs down and test again, All those first 4 bulbs including the "non working 1st one" light up. If I go a few more bulbs down and test again, all those bulbs between the power plug and the test point light up ...EXCEPT now for that first one that had just worked.

-Last curiosity. Led keeper keeps mentioning how the lights current are directional, hence, when you trigger a point in the line, bulbs light up on one side or the other of it. It's kind of the basis behind their method. In a few sections I tested, I am sometimes seeing bulbs light up on both sides of the test point? Usually one side is more lit, and the other side is lit but fairly dim. A few spots both sides of the connection are fairly lit.

Sorry for all the information above, but it's a weird situation that seems to contradict my understanding of how this should work or what to expect. Any input appreciated

 

[XmasinVancouver]

In section 2, it seems to me to indicate a ac to dc power problem.

Hmmmm. I mean technically with the LED keeper I'm feeding DC from a 9v battery. So that thinking could explain why AC source isn't working. I haven't come across any mention of this kind of issue with LED strings/repair though. Doesn't the amount of bulbs in a section get divided by the AC to spread it out until each is getting that lower Voltage? Now that I think about it....how is the AC getting switched to DC in a string like this? Especially as I don't see any canisters or structures on the string other than the plugs, sockets and wire.

 

[error650]

The very first LED after the power connection in section 1 doesn't work when powered from A/C? And yet, everything else (other than the above section 2) works fine with this first LED not working (What happened to the whole "if one failure, the rest won't work in that series"?). Weirdly, that bulb tests perfectly in the led keeper test socket. If I pull that bulb that doesn't light up when it's on A/C, none of the string works (which is what I kinda expected). But when I put it back in, the whole string lights again despite that first LED still not turning on. Here's the kicker again: the wiring to that first led is one wire going directly from the plug to the socket, and 2 wires coming out of the socket to go downstream. Using led keeper on that first wire between the wall plug and the first LED doesn't do anything, but using it on one of the 2 wires that exit the LED socket it lights up fine!? If I go down the line a few bulbs let's say 3 bulbs down and test again, All those first 4 bulbs including the "non working 1st one" light up. If I go a few more bulbs down and test again, all those bulbs between the power plug and the test point light up ...EXCEPT now for that first one that had just worked.

1) LEDs are designed to fall to short while incandescents failed to open. When a bulb fails right, it shorts the contacts and allows current to pass along the string. But, with fewer LEDs now in that series but handling the same voltage across the series, each LED will have to handle more power to balance the load... Resulting in more LED failures in that series if the power busts what each bulb can handle.

2) The first and last bulb in a series have 3 wires. Two are either the hot or neutral AC bus, and the third is the lead to the next bulb in the series. The hot or neutral enters the first bulb and is splices to the lead that runs hot/neutral in parallel to the next series. Look at the wire entry. You'll see that 2 wires enter together and are separated by a plastic divider (the bottom of the bulb socket) from the third wire. That third wire, the one that runs to the next bulb in the series, is the one you need to test with the LED keeper. Cleaning into one of the other wires will short the test probe to the DC+ or DC- (depending on the wiring of your string, if your maintained polarity, etc) from your LED keeper.

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