How to Repair a Dynamic Microphone

Microphones with dynamic elements are the industry standard for live performance. Ruggedly designed, they are able to withstand rough handling and difficult environmental conditions better than their delicate condenser and ribbon element counterparts. Like any piece of electronic equipment, they are susceptible to damage under extreme conditions. Fortunately, they are relatively easy to repair with a little patience and electronic soldering skills.

Internal Parts and Function of Dynamic Microphones

The heart of a dynamic microphone is its cartridge. Dynamic cartridges are integrated assemblies consisting of a cup-shaped diaphragm and electromagnet very similar to a speaker. The integrated design isolates and protects cartridge components from atmospheric conditions and provides reasonable impact protection.

Sound causes the diaphragm to vibrate, and the electromagnet converts vibrations into electrical signals. The signals are sent to a small transformer and are routed to the microphone cable connector. Some dynamic microphones feature an on/off switch.

What Can Go Wrong

Repeated impacts can alter the balanced placement of the diaphragm, causing free movement to cease. The accidental introduction of voltage through the microphone cable can burn out the wiring, transformer, cartridge or all three.

Internal wiring and connections are well-protected and secured, and they won’t fail unless high voltage has caused damage or improper wiring modification has been performed. Poor wiring repair may result in a weak solder joint or improper connection.

Microphone Troubleshooting

Effective troubleshooting of all electronic equipment is best performed by inspecting obvious components first. If a microphone stops working, swap it with a known working unit. If sound is still not present, change the cable. Ensure that the amplification device is operational, and that the on/off switch is in the “on” position.

Internal Troubleshooting and Repair

If the microphone itself is deemed to be the culprit, unplug the microphone cable and proceed with internal troubleshooting.

A voltage meter or continuity tester is handy to check wire continuity from end to end. Begin by carefully disassembling the microphone, starting at the cable connection end. A small set-screw on the lower outside housing secures the connector. Some set-screws will remove from the housing, while others screw inside to free the connector.

Gently pull out the connector with needle-nose pliers, and inspect all solder joints and wire insulation for burning or fraying. If a solder joint or wire end is loose or frayed, re-solder the connection. If burned insulation is evident, further investigation of other components is required.

The microphone transformer is between the cable connector and cartridge, or may be integrated into the cartridge itself, making inspection difficult or impossible. If the transformer is visible, check for obvious signs of scorching of the unit and connecting wires, and check the integrity of the solder joints.

If an on/off switch is installed, remove the two external retaining screws and gently pull out the unit. Inspect the wire and solder joints and move the switch back and forth, feeling for positive switching action. If the switch feels sloppy, bypass it by disconnecting the wire from the switch, making a temporary splice. Plug in the microphone to check for operation.

Most operational problems with dynamic mics are due to cartridge failure. Since the cartridge is sealed and engineered to fine tolerances, repair is generally not possible and requires replacement.

Remove the grill covering by unscrewing it or removing any retaining screws and gently lift out the cartridge. Inspect wiring and resolder if problems are evident. If the wiring is sound, assume the cartridge to be faulty. Write down any numbers printed on the cartridge, and the full model number of the mic. Contact the manufacturer or your retailer to order replacement parts.

Installation of cartridges, transformers, switches and cable connectors is a simple operation, requiring soldering the new components in place. Be certain to label wires as to their original positions. To enhance the cosmetics of your newly repaired microphone, exterior metal grills are also available at a reasonable cost.