Microwave Oven Capacitor

How to discharge a microwave oven capacitor?

One the most important parts of the microwave is the capacitor. While it is important in the functioning of the appliance, it can store a lot of voltage and take a long time to discharge.

If the microwave is repaired before discharging the capacitor completely, it can cause serious damage.

The best way for the capacitor to discharge is to connect the two ends with some resistance. As soon as a resistance is introduced the voltage differential between the terminals will result in a current flow which will discharge the capacitor. When it comes to the microwaves though, this voltage differential is very high and using the standard 1-2W wires will not suffice. This can cause more damage than solve the problem. We need high wattage, high resistance cables to safely discharge the microwave oven capacitor.

Most microwave oven capacitors have a safety feature known as the bleeder resistors.These are just the high wattage resistors that allow the capacitors to discharge as soon as it is stopped. However, like all circuits and setups, the bleeder resistors too get worn out with time.

When this happens, they do not discharge the capacitor completely leave too much voltage trapped in there. As a result, an accidental shorting can result in sparks and this can cause harm to the technicians working on the microwave. The best safety solution is to manually discharge the capacitor. There are two ways of doing this.

Screwdriver Discharge

Tools needed: 20000 W, 2 W resistors, a screwdriver, a pair of wires with crocodile clips. Procedure:

Connect the loose wires to the loose ends of the high ohm resistor with crocodile clips.
Wrap one end of the wire to one of the terminals of the capacitor.
Wrap the other wire to the shaft of a screwdriver
Now carefully touch the screw driver to the other terminal of the capacitor.
Some capacitors have 3 terminals and you need to perform these steps on each pair of capacitor terminals.

Safety Precautions:
When you bring the screwdriver close to the capacitor terminal there can be sparking. This is called arc welding and you must guard yourself from this.

High Wattage Resistor Discharge

Tools Needed: 5 to 50 W /V resistor, 100000 W, 5kV and high wattage resistor Procedure

Fasten the ground wire to any point on the chassis that is exposed to let the charge flow to the ground
Now touch the other end of the resistor to each terminal of the capacitor, one at a time.
This should discharge the capacitor within a matter of a couple of seconds
To ensure the capacitor is fully discharge, short the two ends of the capacitor with a screwdriver. If there is some residual charge it will spark and discharge completely.
To ensure that the capacitor does not build up charge short the two end of the capacitor with a simple wire. In case you forget to remove this at the end, it will result in blown fuse; but it provides a very good safety protection while you are working on the microwave.

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