XLR cables are the primary instrument cables used for audio recording and live performances. XLR cables utilise a female end and a male end on opposite ends of the cable. The male XLR connector is inserted into the mixer or the PA head and the microphone is inserted into the female XLR connector. The male and the female connector have three wires that are soldered to three pins inside the XLR connector. A faulty or bad XLR cable may be the result of a number of things ranging from dirt and contamination, to loose or broken wires.
Replace the suspected bad cable with a different cable. Unplug the cable from the microphone and PA system and use a different cable in its place. If the new cable works fine then this verifies that the other cable is actually bad. If you have similar problems with the new cable, you may have a problem with the microphone or with the PA.
Replace the old cable and diagnose the problem. Check the jack connections. Make sure that the XLR connector and the microphone make a firm connection. Inspect the opposite connection where the XLR cable is plugged into the mixing board or PA head. Hold the XLR cable tightly and flex the cable behind your hand. If the cable wire has a break or short, this will reveal the spot where the connection is broken or weak. The sound will cut in and out.
Wiggle the connection between the XLR connector and the microphone and the connection between the opposite XLR connector and the input jack on the mixing board. If wiggling the connection produces a noisy sound, you may have a loose connection inside the XLR connector.
Remove the XLR cover from the cover to reveal the XLR pins and wires. The cover is held in place with two or three screws. Unscrew the cover and slide the cover down onto the XLR cable.
Inspect the pins and the wires. XLRs have three wires connected to three pins on both the female side of the cable and the male side of the cables. The pins are labelled "one," "two," and "three" and the wires are colour coded. The shield/ground wire is bare and connects to pin No. 1. The positive wire is red and connects to pin No. 2. The negative wire is blue or black and connects to pin No. 3. Determine if the pins are dirty, bent, or if one or more wires is loose or disconnected.
Spray the pins with contact cleaner. Gently wipe the pins and connections with a Q-tip. If the wires are not loose or broken and the pins are in good shape, cleaning the pins with contact cleaner will probably solve the problem. Sweat, dirt, and debris that works itself into the XLR connector can interfere with the electric signal producing strange noises and hums. Test the cable after cleaning the pins and see if the problem is corrected.
Gently straighten bent or crooked pins with a pair of needle-nose pliers.
Solder broken or loose wires. Plug a soldering iron into an electric wall outlet. Use a vice to grip and hold the XLR connector in place while you work on it. Solder the wire to its proper pin. If the end of the wire is frayed, clip it off. Strip off one-eighth-inch or less of insulation with wire strippers to reveal a fresh wire end. Hold the wire to the pin with a pair of pliers and solder it in place. Hold the wire for a few minutes while the solder hardens and cools down.
Reassemble the XLR connector. Slide the cover back into place. Insert and tighten the screws.