Be very careful when handling your microwave, even if you just want to replace the fuse. Microwave ovens use higher voltages than most other household appliances and can cause injury or death if mishandled. Replacing the fuse in a microwave oven should only be done by someone with experience with electrical devices.
Part 1 of 3: How to disassemble the oven
Step 1. Assess your experience with electrical appliances
Even when turned off, the microwave oven contains high voltage capacitors that can cause serious injury or death. While replacing a fuse is a fairly straightforward (but not necessarily safe) operation, a blown fuse is often indicative of other, more serious problems with the instrument. If you are inexperienced in repairing electrical devices, contact a specialist.
Step 2. Take precautions
Microwaves are one of the most dangerous household electrical appliances. Before proceeding with the repair, protect yourself as follows:
- Remove all jewelry and watches - they conduct electricity and can get caught on parts of the appliance. In addition, the magnetic components of the microwave oven can damage the watch.
- Wear rubber-soled shoes and consider using non-conductive rubber gloves.
- Ask someone to be present when the fuse is replaced so that they can call emergency services if necessary.
- Be careful not to touch metal parts inside the microwave oven, especially electronic boards and capacitors.
Step 3. Unplug the power plug from the outlet
If the microwave is built under a kitchen cabinet, the cable may be pulled behind the cabinet.
Step 4. Take out the grill grate
This grate is usually located at the top of the microwave oven and is attached to its top surface with two screws. Remove the screws, pull the grate (usually left or up) and remove it from the plastic hooks. Set the grate aside and mark the location of the screws you removed.
- On some models, you must open the microwave door to access the grill rack.
- On some models, the grill grate is located at the back of the oven. In this case, it does not need to be removed, since it does not interfere with access to the rest of the parts, although sometimes the fuse is located behind it.
Step 5. Remove the control panel
Locate the screws on the control panel, which can be accessed after you remove the grill grate. Remove the screws on the top of the panel. Lift the panel, pull it forward and slide it. Leave the panel in the open position without disconnecting the appropriate wires.
Step 6. If necessary, remove the outer panels
As a result, you will gain access to some of the internal parts of the microwave. Now you can check the integrity of the electrical circuits or unscrew and remove the remaining panels for full access to the internal parts.
Part 2 of 3: How to discharge a capacitor
Step 1. Wait a few minutes (preferably)
A life-threatening charge may remain in the condenser even after you unplug the microwave oven. Although the charge must drain from the capacitor after stopping the oven, it may take several minutes to discharge. Even after you wait, do not rely on the capacitor being completely discharged. It may fail, or it may turn out that this safety measure is not provided on your model.
Make sure the microwave oven is unplugged before proceeding
Step 2. Find the capacitor
In most models, the capacitor is a metal cylinder with two or three electrical contacts. If you cannot find a capacitor, contact a specialist. Never disconnect internal parts while looking for a capacitor.
Do not touch any part of the inverter circuit to which the capacitor is connected. The aluminum cooler, windings and choke coil can carry high voltages
Step 3. Choose a screwdriver with an insulated handle
You can also wear rubber gloves, especially if you don't know how much voltage the handle is designed to handle. The electrical voltage can be up to 5000 volts.
Step 4. Attach the resistor to the tip of the screwdriver
Use a 100K ohm resistor 25W or higher. This will slow down the discharge and prevent possible damage to the screwdriver or microwave parts.
Step 5. Connect the other end of the resistor to the metal chassis
Use a crocodile clip to clip the other lead of the resistor to the metal chassis of the capacitor. In this case, it is recommended to use rubber gloves so as not to accidentally touch the capacitor contacts with your bare hands.
Step 6. Touch the metal tip of the screwdriver to one of the capacitor outputs
Hold it there for a few seconds to drain the entire charge.
General Electric's instructions for JES microwave ovens indicate that the circuit can be discharged at the filament terminal of the magnetron
Step 7. Do the same with the other contact
Make sure the resistor is still grounded and touch the other terminal of the capacitor with the tip of a screwdriver.
If the capacitor has a third contact, do the same with it
Step 8. Check if there is any electrical charge left
Move the screwdriver aside and disconnect the resistor from it. Touch the tip of a screwdriver to one and then to the second output of the capacitor. If there is a pop or a spark, the capacitor has not been fully discharged. Although the voltage should disappear after this, if the capacitor is not fully discharged, it is necessary to reconnect each output to ground.
Never check the voltage with an ordinary multimeter. Standard multimeters are not rated for the high voltages used in microwave ovens
Part 3 of 3: How to Replace Fuses
Step 1. Check for obvious signs of breakage
A burnt-out protection usually indicates a problem in the electrical circuit. Look for traces of burning, dead insects or other debris in the electrical circuit, broken or melted parts. If you find these symptoms, in addition to replacing the fuse, you will need to replace or repair the failed components.
- A fuse can burn out for a variety of reasons, the description of which is beyond the scope of this article. It often burns out due to a broken door interlock contact, in which case it is necessary to replace several components on the door or adjust it.
do not touch unknown parts or try to disconnect them. If you are unable to identify the defective part or you do not know how to safely work with high-voltage equipment, contact a specialist.
Step 2. Find the fuses
Microwave ovens use two types of fuses. This can be a conventional fuse in the form of a ceramic tube about 3 centimeters long. Thermal fuses are also used, which are usually in the form of a wide black cylinder with two wire contacts on one side. The location of the fuse depends on the specific model. Check behind the control panel first.
- If you find it difficult to find fuses, study the electrical diagram, which is usually printed on the inner lid of the microwave oven (and sometimes on the bottom or back of the outer panels).
- Sometimes fuses are hidden behind other parts. Only remove these parts if you are familiar with their purpose and know how to safely remove them.
Step 3. Pull out the fuses carefully
Remove the fuses using a fuse pliers or a screwdriver with a securely insulated handle. To remove the thermal fuse, pull the wires out of the slots. Remember where each fuse was.
Step 4. Check the fuses with a multimeter
Typically, the appearance of fuses used in microwave ovens does not change when burned. To check the fuses, set the open circuit test mode (if any) on the multimeter, which corresponds to the symbol ))).
If there is no such mode, set the smallest resistance measurement range. Check the resistance of the fuse:
- Touch the probes to each other. In this case, in the open-circuit check mode, you should hear a characteristic sound. If the multimeter is set to resistance measurement, it should read 0 ohms (an analog multimeter may require pre-calibration).
- Touch the probes to the opposite ends of the fuse.
- If the multimeter shows 0 Ohm or emits a characteristic sound, then the fuse is intact. If the multimeter shows non-zero resistance, "OL" overload or does not beep, then the fuse is out of order.
Step 5. Replace the blown fuse with a similar one
The new fuse must have exactly the same dimensions and current range as the blown one. The fuse specifications are indicated on its body, although the inscription may be very small, in which case a magnifying glass will come in handy.
- Insert the new fuse into the appropriate slot. When doing this, use a safety pliers or rubber gloves.
- Buy some spare fuses. If the previous fuse is damaged due to some malfunction, the new fuse may also blow.
Step 6. Assemble the microwave
Place all previously removed panels and secure them in the reverse order of how you disassembled the oven. Make sure all panels are securely in place and do not pinch the wires. Improper assembly may result in radiation leakage from the microwave oven during subsequent operation. Make sure all screws are back in place as some of them may be responsible for grounding the cover.