somuchdirt74 :
americanaudiophile :
There don't seem to be any bad solder joints but it is hard to tell. You need to check that the speaker itself is not bad. You can apply a headphone level signal to the speaker itself at the point where the red and black wires are soldered.
There may also be a broken wire going into the headphones.
I'm not sure how to apply a headphone level signal to the speaker. I tried looking that up online but I'm not really sure what you mean by it or how to do it.
The pictures are not all that great but I can submit more if I need to. The red and black wire are twisted to each other, they are not soldered to anything in the area where they are joined. The other end of the red wire is soldered. The thick grey wire is only soldered to one side while the other part of the part is just dangling, it is not soldered.
As best I can tell from the pictures here is how it is wired:
left side: the input cable from the plug has three wires - red, green, and black. The green seems to be the left signal, the red the right signal, and the black is common. there is a black wire with two conductors which i see leaving l=the left and heading toward the right, but it's not clear how it is connected on the right side.
I see a red wire going from what looks like the interconnect to the right speaker with another red wire. If the gray wire is truly hanging loose, it is likely the common for the right ear, and needs to be connected to the other conductor of the interconnect.
----
To confirm that the right-channel wire is bad in the cord to the plug, simply connect a jumper fro the red to green wires on the left sie. You should hear something out of the right speaker.
If that does not work, you can confrom that the right speaker is good by running a jumper from the green on the left to the red on the right, and from the black on the left to the gray on the right. if only one of these is needed to get sound, you have found the bas segment of wire, and you can check for loose connections or just replace the wire -> red to red and black to gray.