If you’re attempting any repairs on a microwave oven, knowing how to discharge a microwave capacitor is a must beforehand for safety reasons. Even the best microwave ovens are capable of delivering dangerous shocks and being damaged if not properly discharged, so it’s an absolutely essential part of your DIY repair skill set.
The high-voltage capacitor or voltage microwave capacitor is a device in a microwave that provides additional voltage to the magnetron (which is responsible for outputting the actual microwaves) because magnetrons require at least 240V as opposed to the standard 120V most home power sources provide to an appliance and is sometimes the culprit when the microwave is not heating food.
You don’t need a specialized tool to perform a discharge, although capacitor discharge pens are available.
It will store large amounts of electricity much like a battery holds a charge even when it’s unplugged, and that power must be released safely before any microwave repair, such as fixing or replacing a magnetron or it can cause a potentially fatal shock and damage other microwave components.
First, you’ll need to following tools:
The capacitor is discharged by causing a short circuit between each capacitor terminal and the capacitor’s metal chassis. It’s advised to thoroughly read all the steps before beginning. Once you’ve unplugged the microwave from its power supply and dissembled the oven to get to the capacitor, make sure you’re wearing your rubber gloves and:
Make sure all your tools including your gloves are rubberized before attempting a capacitor discharge, or you risk a serious shock.
How much power is in a microwave’s high voltage capacitor?
The capacitor will store between .95 and 1.00 microFarads (the energy rating capacitors use) even when the oven is unplugged. It takes the standard 120 volts from your home power outlet and amplifies it to the 1000-3000 volts needed to power the magnetron and heat your food.
Can a microwave capacitor hurt you?
Any electricity is potentially dangerous to humans, and a capacitor stores electricity for long periods of time even when not attached to an outlet, amplifying that power greatly beyond the standard 120V in conjunction with a resistor and diode. Improper handling of a capacitor is highly dangerous.
Is there a dedicated capacitor discharge tool available?
Though you can use a rubberized screwdriver or pliers, specialized capacitor-discharge pens are available and can make it easier to do the job, as long as the pen is rated within the capacitor’s voltage. Additionally, having access to a multimeter can help in troubleshooting.
STAT: From 1990 to 2010, microwave-related injuries increased 95%. (source)
STAT: It’s estimated that there are about 6,600 home fires started by microwave ovens every year. (source)
STAT: Contrary to popular belief, microwave ovens do not, in fact, cook food from the inside out. (source)