Question about Magic Chef CMV1000B Microwave Oven
Fuse: Take off the plastic airflow cover: In the Upper Right Hand Corner has a grey screen covering the Fuse: 125v -250v 20A Inline.
Posted by Anonymous on
SOURCE: Replacing the fuse of a MCO160UW
A microwave can be dead for many reasons.
It may be the fuse, which is usually located on the floor of the oven behind the control panel or between the door switches.
If the fuse is good, it may be an open thermostat or thermal cutout (TCO) / thermal fuse on or near the magnetron or on top of the cavity / body of the oven.
If it goes dead for a while during or after cooking then comes back on, the magnetron is probably overheating and causing the magnetron thermostat to open.
Then when it cools, it closes the circuit and allows power through again.
When checking thermostats, if it has a hood fan thermostat, that should read open, as opposed to the others, which should read closed.
If it went dead almost immediately after pressing the Start pad, that's usually a shorted high-voltage capacitor.
If it went dead a few seconds after pressing the Start pad, that's usually a failing high-voltage transformer.
If it goes dead or blows the breaker (or GFI) when you plug it in or open or close the door, then there's a problem with a door switch or door switch mount.
If it's intermittent or random, it may be a bad connection, usually on the control board or a loose fuse holder, or even an intermittent fuse.
You should do a continuity test on the fuse while it's in the holder (with the microwave unplugged, of course) then turn the fuse by hand or take it out and put it back in, then test it again.
If you remove the fuse, then press the meter leads against the ends, it can allow internal contact to be made and make a bad fuse appear to be good.
If you or someone you know decide to look into it, we have critical safety information and disassembly information at our site, and our link is at our listing here on FixYa.
There may also be a "mini-manual" hidden inside the unit behind the control panel or hidden on the left side behind the grille, which is very helpful when troubleshooting & testing.
We're happy to help you and we'd appreciate your thoughtful rating of our answer.
Posted on Jul 19, 2008
Bad door switches normally don't cause fuses to fail. Typically there's 2 of them wired in series with each other so if one of those switches fail to turn off power the other one will when the door is opened.
There are a number of components that can cause a fuse to open; HV diodes, capacitors and fans, to name the most common culprits, and require the knowledge and safe use of a volt-ohm meter to efficiently find the problem.
Posted on Jun 15, 2014
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