How to Remove the Bleeder Resistor in Microwave Capacitors.

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Introduction: How to Remove the Bleeder Resistor in Microwave Capacitors.

In this instructable, we will discuss how to remove the bleeder resistor from the medium sized metal can capacitors such as those found in microwaves. This will not work for all capacitors. Some have an internal resistance which cannot be removed. The Samsung units, like those pictured below, are known to contain a removable resistor.

Please note that this is extremely dangerous, not to mention messy. If the resistor isn't working in the first place, chances are that the capacitor will already be holding a potentially lethal charge. Removing them ensures that it will be capable of holding a lethal charge. ALWAYS short the terminals before working with a capacitor. This is about as dangerous as climbing telephone poles. I don't recommend that anyone try this. Enter at your own risk!

Step 1: Gather Necessary Tools

Here is what we will need for the task:

0.99 The capacitor(s) you're going to mutilate of course
1. Nibblers or some type of cutting tool (the ones I used were purchased at Radio Shack)
2. RTV Silicone sealant (automotive section)
3. A work surface, preferably outside, that you don't mind getting full of nasty smelling oil and
brake cleaner
4. Brake Cleaner (rubbing alcohol may be substituted, but it won't work nearly as well)
5. Side Cutters
6. Mineral Oil (optional in case too much of the original oil is spilled)

Step 2: Hack Open the Capacitor

The first step is to open the capacitor. Using the nibbler, cut all around the top of the can. Try to keep it upright to minimize the loss of oil. All that is needed is to cut down through the first layer of metal and move to the next spot. Strong hand muscles are definitely a requirement.

Step 3: Pop the Top

Now once you have cut all the way around, the top should just pop right off. Grab the terminals and pull. If it doesn't come off, that means you need to do more nibbling.

Step 4: Remove the Bleeder

If your capacitor is equipped with a standard bleeder resistor, you will find it making a connection between the two terminals just under the "cap". On these it was under the paper flap as in the picture below. These Samsung types use a special high voltage thin ceramic resistor. Either bend it back and forth until the metal fatigues, or cut it out with the side cutters. You can throw them away, but I save them for interesting things.

Step 5: Slop the Slop

Now that the bleeder is removed, add some mineral oil if the oil level fell below the top of the paper down inside. Put the "cap" back on and spray the brake cleaner all over the outside to remove all traces of oil. The RTV won't stick properly if there is any trace of oil on the outside. I alternate between spraying and wiping with Kleenex.

Once it's clean and dry, slop the RTV around the seam to seal things back up. It should look like the picture below. Put it somewhere out of the sun and where it won't be getting hotter to dry. If the temperature of the capacitor increases now, it will force the oil out of the seam and make a channel through the RTV and leak. You might need to brake clean and RTV several times like I did to eliminate all the oil leaks. All done! Enjoy your new extremely dangerous capacitor toy thing. When not in use, you would be wise to keep the terminals shorted with alligator clips or a jumper wire with disconnects on the ends like I have below.

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    user

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    40 Comments

    I don't want to be the safety nazi, but you brought up the possibility that the bleeding resister has already failed open, and the fact that the cap may already hold a charge. Shouldn't we short the terminals first, just in case?

    Hopefully those attempting this will know that already, but I'll add it just in case.

    user

    I would suggect using oil from a donor capacitor, not engine oil. I'd fear the additives in engine oil might have a bad effect. As for the silicone, wouldn't it be possile to solder the capacitor shut? Finally, some really old ovens use an external resistor. Those are obviously the easiest to remove :)

    Use only new mineral oil. Solder does not stick to aluminum. Some capacitors are steel though and you can try soldering them, but if the heat causes the oil to come out the solder will not stick.

    they can be soldered shut no worries!!

    How big is the resistor?

    How does it look?

    And I don't understand why do you need the RTV and the mineral oil, Did you want to remove the resistor, and then use the capacitor without the resistor?

    Wow! Capacitor Surgery. Resistor-ectomy. I am impressed!

    What are you after in removing the internal resistor of a capacitor?

    Anyway, my problem is a busted microwave oven capacitor of these specs:

    2100V.
    AC 0.82µF ±4%b

    SAMHWA CAPACITOR CO. LTD.

    from an old Whirlpool with mechanical knob controls microwave oven.

    I am having a hell of a time finding a replacement.

    Can it be repaired at all.

    With the resistor in there, I would need a powerful transformer to charge the capacitor. With it removed, it can be charged by something much weaker, such as a flyback driver.

    For your capacitor, if you are sure that is what the problem is, it doesn't have to be an exact replacement. Anything that is equal to the voltage and farad rating or greater will work. For instance a 2400V 1µF capacitor will work just fine. I think that is a much more common size.

    Thanks for your kind attention.

    If I may, you sure are adventurous, because now I know that the internal bleeder is to dissipate the charge inside, so that it is safe or safer for repair people to service the oven.

    Your purpose is to be able charge the capacitor faster with the internal bleeder resistor removed?

    Well, that is adventurous, and also perhaps you would rather also save money from not having to buy a quick charging capacitor?

    I am not any electronic engineer or hobbyist, etc., but you are one study of a stubborn what I might call a re-cycler -- it takes all kinds, though.

    Glad to meet you, and thanks for the conversation.