Total Blackout: Fixing a Microwave with No Power or Display

** Warning avoid the capacitor inside these and do not open case with it plugged in** This is usually either a blown fuse ~ beware of what caused the blown fuse as something may be damaged internally. It could be the tco thermal cut out that has operated due to overheating.

Photo below shows 2 thermal cut outs monitoring the temperature of the oven cavity and the magnetron temperature obviously if these get to high the tco with open and shut microwave down.

⚠️ Safety Note: The "Silent" Killer

A microwave with "no power" might seem safe, but the high-voltage capacitor doesn't need the wall socket to be dangerous. It stores thousands of volts. If you are testing the TCOs or fuses, keep your hands and tools far away from the large silver cylinder (the capacitor).

A microwave that won't turn on at all—no lights, no LCD, no fan—is often suffering from a simple break in the electrical circuit. Before you bin it, there are two primary "gatekeepers" of power you should check with a multimeter.

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The Repair Process

1. Safety First: NEVER open the case while the unit is plugged in. Even when unplugged, the high-voltage capacitor inside can hold a lethal charge. Avoid touching it at all costs.

2. The Thermal Cut-Outs (TCOs): Most microwaves have at least two TCOs. These are safety switches that "trip" (open) if the unit overheats.

   • Location: One is usually on the oven cavity, and another is on the magnetron.

   • Testing: With the power off, use a multimeter to check for continuity across the terminals of both TCOs.

   • Result: If either shows "Open Circuit" (no continuity), it has failed or tripped and must be replaced to restore power.

3. The Main Incoming Fuse: Check the ceramic fuse located near the power cord entry point.

   • Testing: Test for continuity. If it's blown, power cannot reach the control board.

   • Caution: A blown fuse is often a symptom, not the cause. If a new fuse blows immediately, there is a secondary fault (like a shorted magnetron or capacitor) that needs further diagnosis.

Above 2 x thermal cut outs to check for continuity

below the main incoming fuse check this as well

There can be two tco I missed this in filming the below video so be ware of this when you troubleshoot.