Test a Metal Oxide Varistor
- 1.Unplug the device containing the MOV from the wall outlet. Unscrew the case and open it.
- 2.Identify the fuse inside the case. Remove the fuse and examine it. If the fuse is blown, set it aside and make a note to replace it. Identify the metal oxide varistor. In most smaller equipment, it is a two-lead, coin-sized device, similar to a disc capacitor with a bright colour, such as red, yellow or blue. Note if the MOV appears to have burn or scorch marks, indicating damage.
3.Touch the tip of the hot soldering iron to one of the MOV's leads to melt the solder, then draw off the solder with the desoldering pump. Work the lead loose with a long-nose pliers.
4.Turn the multimeter on and set its function knob to read resistance. Touch the meter probe tips to the MOV's(Metal Oxide Varistor) leads and measure its resistance. If it has a resistance much under 100 ohms, it has blown. Desolder and remove the remaining lead and remove the MOV from the equipment. If the part has resistance over one million ohms, it is still good. If it's good, resolder the lead you removed in step three. If it's blown, remove the lead that's still connected.
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