Instructables

Step 4: Discharge the capacitor

Picture of Discharge the capacitor
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Locate the capacitor, it should be near the big fat chunk of metal, the high voltage transformer. Then get your alligator clips and very carefully touch both terminals of the capacitor...

You may get an loud "SNAP" (which is unlikely) and that indicate the capacitor is discharged, do this a few more time to really make sure the capacitor is discharged..

And you're done! The microwave is safe to gut out!
 
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If you REALLY want to be safe, use a HEAVY bladed screwdriver (preferably one from a yardsale - cheap, and you don't care if the super-powerful electrical arc pits the metal!) then measure the voltage on the cap with a multimeter set on highest setting. Better to blow up a cheap meter (such as those sold @ harbor freight) than.. to die.
i've also heard it said that when one is in a tight spot (as this one looks to be) use two junk screwdrivers crossed so they are touching (hold one in each hand). that way, you don't have to get in at a right angle to the cap to touch it or get really close like with the alligator clips.

also, using two, if you are startled and drop them, they will always fall OFF of the cap. using a single screwdriver, you will occasionally weld the screwdriver to the cap you are discharging.

just some thoughts.
Vulnic3 years ago
I'm still very concerned about discharging the capacitor. Would it make it any safer to use one of those wrist chords used when building/fiddling around inside a computer to clip onto something metal and ground you?? I mean it's not as if you get another shot at this if it goes wrong.... like they say 'There's not many DUMB electricians left in the world ... they're all dead"
strongclad5 years ago
I've read elsewhere on the internet (http://www.doityourself.com/stry/repairmicrowave) that you should go about discharging the capacitor another way. Is this a better/safer way of discharging the capacitor?

"you will need the following: a screwdriver, a wire-wound resistor with a 2 watt-20,000ohm rating, and a pair of jumper wires with alligator clips on the ends. Clip a wire to each end of the resistor. Clip one wire to the metal shaft of the screwdriver. Clip the other wire to one of the capacitor's terminals. Now, touch the other terminal with the tip of the screwdriver. There may be a small spark. If the capacitor has three terminals, do the same process with the middle terminal and each outside terminal."

I've also read that you should do the same from each terminal to the chassis.
Plasmana (author)  strongclad5 years ago
His method is safer, however, I prefer to do the simple and harsh way, lol.
What about the screwdriver? I've gone looking for one that has a well insulated handle, but I can't find any that list this feature on the packaging. The only screwdrivers I've found that say so explicitly are ones that also insulate the entire shaft except for the tip. Are there any screwdrivers that you may know of that insulate only the handle?
Yes, the ones with a rubber or plastic handle.
bobbyrae5 years ago
This looks wrong! Connecting a wire to both sides of the capacitor will do nothing! You have to connect each side to GROUND, one at a time.

Hey folks, here' s link to a guy who understands microwave repair really well:
http://www.repairfaq.org/sam/micfaq.htm. Has better details on doing this discharge thing.
melkor801425 years ago
is it just one alligator clip w/ the opposite both sides touching opposite sides of the capacitor.