A varistor acts as an open circuit under normal operating voltages but rapidly drops its resistance when the voltage exceeds a specific threshold. This clamping action diverts transient surges away from sensitive components, converting the excess energy into heat. Metal-oxide varistors are the most common type found in power strips and input protection stages.
Check the varistor on the input stage, it probably blew during that lightning strike.
A varistor degrades slightly every time it absorbs a surge, eventually failing short and blowing the inline fuse.
Also heard as
- metal-oxide varistor
- MOV
- voltage-dependent resistor
Related terms
MOV
A metal-oxide varistor is a voltage-dependent resistor used to protect circuits from voltage spikes.
Resistor
A passive two-terminal component used to limit current flow, divide voltages, or terminate transmission lines.
Zener diode
A specialized diode designed to allow current to flow backwards when a specific reverse voltage is reached.