Ensure that you have correctly diagnosed your amplifier's problem before you attempt to remove any electrical components. Capacitors are primarily responsible for removing the electrical hum caused by your power source. If the capacitor has failed, this hum will be continually present while your amp is powered on. Any notes played on your instrument will be accompanied by a pitched drone. In addition to the hum, your amp will become incapable of producing louder volumes and the overall tune will distort and lose clarity.
Locate the capacitors inside your amplifier. Capacitors are large metal cylinders found inside the chassis of your amplifier near the transistor tubes. It is highly recommended that you do not attempt to replace these items on your own, as capacitors often carry a lethal amount of electricity. As capacitors still maintain electrical charge after being unplugged from your amplifier, do not touch these devices until you have drained their power.
Measure the remaining voltage in the capacitor using a multi-meter. Configure your meter to read DC voltage, and adjust the range of the multi-meter so that it is capable of recognizing over 500 volts of charge. Connect the black lead of your multi-meter to the chassis of your amplifier. Keep one hand away from the meter and chassis, and use your other hand to measure the voltage level across a DC capacitor in your amplifier. Any readings above five volts render your amplifier a threat.
Clip one side of your capacitor discharge tool to the chassis. Using your insulated pliers, pick up the second clip on the discharge tool and connect it to the first or sixth pin on the first preamp tube. After five minutes, use your multi-meter to check the voltage levels in the capacitors. Repeat this step until the capacitors are holding less than five volts of electricity. Capacitors may slowly begin to recharge while you are working inside your amp. Have your discharge tool close at hand to repeatedly drain your capacitors.
Remove the drained capacitor and replace it with your new product, ensuring that the poles of the capacitor are properly aligned. Incorrectly plugging in a capacitor may cause the device to explode. The poles of the capacitor are clearly marked and should be aligned with the pole indicators on the capacitor's socket.