Hotpoint Microwave: Magnetron Failure Symptoms vs. Blown... | appliancefaults.com

Technical Background:

The MCU controls the microwave's operation, including the magnetron. When you press start, the MCU sends a signal to the high-voltage transformer circuit, which includes the high-voltage capacitor, diode, and magnetron. A blown fuse usually indicates an overload in this circuit. The magnetron generates the microwaves that heat the food.

Symptoms:

US homeowners typically report the following: microwave runs but doesn't heat food, burning smell, popping or arcing noises inside the microwave, or a completely dead microwave with no lights or display.

Possible Causes:

Magnetron failure
High voltage capacitor failure
High voltage diode failure
Overload due to arcing or short circuit
Door switch failure
Line voltage surge

Solution:

1

Unplug the microwave from the 120V AC outlet.
2

Discharge the high-voltage capacitor with an insulated screwdriver and verify with a multimeter that it reads 0V DC. The capacitor stores a dangerous charge even when the microwave is unplugged.
3

Use a multimeter to test the continuity of the fuse. Replace if open. Fuses are typically rated at 15 or 20 amps.
4

Inspect the magnetron for signs of burning or damage. Test the magnetron filament for continuity. Should read close to zero ohms.
5

Test the high voltage diode with a multimeter. It should only conduct in one direction. Replace if shorted or open.
6

Test the high voltage capacitor. Replace if shorted or leaky. A typical high voltage capacitor will be around 1 microfarad and rated for several thousand volts.
7

If all components test good, suspect the MCU (Microcontroller Unit) on the control board, or the door interlock switches. The MCU requires a trained technician to diagnose properly. Use a 1/4-inch nut driver to access components.

Safety Warning:

LOCKOUT/TAGOUT (LOTO) procedure must be followed before servicing. Microwaves contain high-voltage components that can deliver a lethal shock even after being unplugged. Always discharge the high-voltage capacitor.

Prevention:

Clean the interior regularly to prevent arcing. Avoid using metal objects inside the microwave. Do not operate the microwave empty. Regularly inspect the door seals.

Expert Tip:

If the microwave fuse blows repeatedly after replacing it, suspect a shorted high-voltage capacitor or a failing magnetron. To test the door switches, check for continuity when the door is opened and closed. Often multiple door switches will need testing. The service mode for many Hotpoint microwaves can be accessed by pressing and holding the “Clock” and “Timer” buttons simultaneously for 5 seconds. This will vary by model.

Frequently Asked Questions

•How do I safely discharge the high-voltage capacitor?

Use an insulated screwdriver with a well-insulated handle to short the terminals of the capacitor. Verify with a multimeter that the voltage is 0V DC.

•What are the common failure signs of a magnetron?

Visual signs include a burned or cracked anode cap, or a broken filament. Electrical signs include an open filament or a short to ground.

•Where can I find the correct replacement fuse for my Hotpoint microwave?

Check the microwave's service manual or the rating printed on the original fuse. Replacement fuses are available at most appliance parts stores or online retailers.

Hotpoint Microwave: Magnetron Failure Symptoms vs. Blown Fuse Troubleshooting

Technical Background:

Symptoms:

Possible Causes:

Solution:

Safety Warning:

Prevention:

Expert Tip:

Frequently Asked Questions

•How do I safely discharge the high-voltage capacitor?

•What are the common failure signs of a magnetron?

•Where can I find the correct replacement fuse for my Hotpoint microwave?

Related questions

Technical Background:

Symptoms:

Possible Causes:

Solution:

Safety Warning:

Prevention:

Expert Tip: