Short from signal to ground, no sound in that channel.
Short between the two signal wires, you'll have both channels combined, aka a summed mono signal.
Cold solder joint, it will show a slightly higher resistance than a proper solder joint, it will look dull as opposed to shiny, and if you have a magnifying glass you will see little fissures in the solder, it will also be brittle and likely to break under stress.
Using a multimeter, test for continuity between all wires, this will allow you to check for a short.
BEGIN EDIT explanation of above: check for continuity between the tip and ring, tip and sleeve, and ring and sleeve. If you get anything other than an infinite resistance, the state the meter is in when the probes are not touching each other, then you have short. END EDIT.
Then use your meter to do a resistance reading on each conductor, at such a short length your reading should be bellow 1 ohm. If you take and put both probes together, the reading you see there should be about the same as the reading you take on your cable. Example, I have a Fluke digital multimeter, when I place my probes together I get a reading of ~0.02 ohms, when I do a short cable the resistance I read is never above 0.03 ohms, even when doing readings of cable runs through walls of over 100', the reading is not over 0.04 ohms.
If your multimeter shows a resistance >1 ohm, then you have an issue, check for a cold solder joint, if it appears to be that, then reheat the joint and add a very small amount of solder to add flux to the joint. Do not allow the wire being soldered to move until the solder has hardened, if the wire moves while the solder is still in a liquid state you can get a cold solder joint.
A quick question. When you made your connections, did you tin (apply solder to fill a cup, lead, or bare wires) the connector and wires before soldering them together? If not, I would redo the connections.
Edited by samsquanch - 1/22/13 at 10:42pm