How long can a microwave retain an electric charge when inoperable but still plugged in?

How long can a microwave retain an electric charge?  I think I need to change a fuse as the unit completely stopped working when I reset a fuse for the kitchen when I found our refrigerator had stopped running.  I confirmed that it was indeed the microwave and not the electrical outlet that wasn't working.  This occurred 3 days ago.  The unit is still plugged in - how long would I need to have it unplugged before I could safely remove the back cover to get to the diagram or the main fuse to see if it's burned out?  Thanks for any advice on how to do this, we can't afford to buy a new unit and it sounds like buying a new one would be cheaper (or cost the same!) as hiring a repairman.

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Few minutes or so. The mains side should be dead instantly. The HT side that's AFTER the transformer might be hot for bit longer.

If the microwave fuse has gone, its unfortunately highly likely its something you won't be able to fix, unless its something dumb like the bulb !

Steve
luannfeld (author)  steveastrouk4 years ago
Thx for answering me. Turns out the screw on the back of the device are non-removable. We decided to go ahead & buy a new one after all, a last minute Chanukkah gift to the family :)
Depending on what's wrong with it, it could be charged for quite a while. If it hasn't been working for three days I would assume it's safe, however I would still be wary of the microwave transformer and capacitor.

As Steve said if its fuse has blown it's unlikely you can fix it, however I suppose you could try your luck and just replace the fuse and hope it works. (probably outside so you don't burn your place down).

Or you could just find another microwave on the street or at a garage sale for $10, they usually seem to work.
luannfeld (author)  The MadScientist4 years ago
Thx for responding. It turns out the screws on the MW can't come off. My husband & I decided to "bite the bullet" & buy a new one, which we did today.
Have you seen this page?
http://www.repairfaq.org/sam/micfaq.htm

That big capacitor, a part of the the voltage doubler circuit, is the only component which possibly could hold a charge for more than a few seconds after the oven is turned off and unplugged.  The big capacitor is supposed to discharge itself, via an internal resistor, and it probably does, in a about minute or so, as other posters have suggested.

This section of the FAQ linked above,
http://www.repairfaq.org/sam/micfaq.htm#micsafdc
gives some hints for making certain the big capacitor is discharged, if you're one of those people who likes certainty.

By the way, there is more than one "fuse", or fuse-like thing to worry about.  I mean there's the main one, and then there's that thermostat, or maybe it's a thermal fuse, bolted to the top of the cooking chamber, and then there are all those little interlock switches in the door.

I remember I bought a broken microwave at a garage sale, years ago, and for that one it was a broken thermostat.

My parents had a microwave in which they managed to burn up one of those interlock switches in the door, but that is because my mom would often open the door on it without stopping the timer first(naively letting the switches in the door interrupt the current instead).

For the problem with your microwave, I will suggest this handy chart here:
http://www.repairfaq.org/sam/micfaq.htm#mictchart
which seems like as good a place to start as any.