I just received this 300 LED SMD 5050 strip from ebay seller 2012topdeal and upon testing, I found that the last 12 LEDs (from Marker 1 to Marker 3) only work on Blue when powered from the PLUG. I cannot get Red or Green (from Marker 1 to Marker 3) to turn on by powering the PLUG.
Shown in the Photo below is the last 12 inches of the Strip with it's plug.. I cut this from the 15M roll. There are 18 LED's total in this piece.

First of all, ALL the BLUE LEDs work regardless of whether I put power at the PLUG, Marker1, Marker 2 or at Marker 3.

The problem is that when powered from the PLUG, only the LED's up to marker 1 fully work. All the LEDs after Marker 1 only light up the Blue LED.s
However, if I power it from the terminal end at Marker 3, (where it was cut), ALL the LEDs work from Marker 3 to Marker 1. So obviously all the LEDs work.....they just aren't all getting power ( except the BLUE LED's, because of an unknown problem at or near Marker 1.

If I put power at the copper pads at marker 1, ALL the LEDS between marker 1 and marker 3 work normally. But only the BLUE LEDs between Marker 1 and the PLUG work.

So while ALL the LEDs work when powered, it appears there is some problem at Marker 1 so that power is not passing marker one except to blue LEDs when power is applied at the PLUG.

My best GUESS (since ALL the LEDs work when they receive power) is that there is a bad connection between Marker 1 and the first LED toward the PLUG.

Is there any way to repair this?

 

Well, does anyone have a schematic for how this thing is internally wired? I suppose the "tape" is based on the entire ribbon being a flexible PCB?

 

It's probably something like this:

This image was borrowed from the Adafruit website here: https://learn.adafruit.com/rgb-led-strips/schematic

This schematic shows common anode wiring. There are also strips with common cathode wiring.

Repair would probably involve the same scraping and soldering steps down here:
https://learn.adafruit.com/rgb-led-strips/wiring
You just have to find the break point (maybe where there was a crease or sharp, tight radius bend in the material at some point,) then scrape and solder a tiny jumper wire in.

 

Thank you so much!

I couldn't find this information.

VERY helpful

 

I decided to just cut a section off (the bad section) so now I have a section that is about 4" long that contains the problem.

As a learning tool for the future....I may "surgically" remove all the plastic film (if possible) to see the underlying circuit board and the cause of this problem.....and a fix. Fortunately it was a small section near the end but it "could" have been right in the middle.

If I find anything useful I'll post pictures and a summary of what I found (and a potential fix)

Still, when you pay for a 300 light LED strip, you expect 300 working LEDs

 

If it works when powered from the cut end, then the fault is obviously at the plug end to the first leds.

 

If it works when powered from the cut end, then the fault is obviously at the plug end to the first leds.

Well, that's not exactly what I said in the OP. I said ALL the LEDs work, but only in groups, depending on which end it was powered from.

Or at least that what I thought I said. I have to study thew schematic and see if a single BAD LED can cause this issue....but again, since they all work....I ruled out the LEDs as the cause of the problem.....maybe too soon?

 

Ok, then the tracks are broken at the point of Marker 1 and the plug.