What are those hard metalic cylinders

Discussion in 'General Electronics Chat' started by Gdrumm, Mar 12, 2010.

  1. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
    I've a small collection of hard metalic or ceramic cylinders which I've harvested from various electronic devices, and I don't know their purpose.

    They are all black, or charcoal colored, and come in various sizes.
    In most cases, the power cord runs through them in a loop.

    Are they for the elimination of electric static?

    Or are they there for some other reason?

  2. SgtWookie


    Jul 17, 2007
    They are toroids, or baluns. They are used to suppress rapid transients (power spikes) on the power lines [eta] and also to reduce the possibility that the device itself will couple noise onto mains power, like from an internal switching supply.

    They can also be used for all kinds of nifty projects, like power inductors for boost or flyback type switching supplies, boost converters for LEDs, charging batteries, making battery desulfators, transformers and other stuff.

    Here's a great page for learning about boost and flyback type converters made from such salvaged toroids/baluns, and how to determine the approximate value of the toroids/baluns:

    Here's a free helpful downloadable calculator for determining aspects of your toroids:

    For a "quickie" project, try the Joule Thief:
    Your toroids are a bit large for that project, but they'll be easy to wind ;) You won't need more than a couple turns, either.
    Last edited: Mar 12, 2010
    PackratKing likes this.
  3. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
    Great stuff, Thanks
  4. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
    I am now seeing this toroid or balun material in Panasonic Microwave Ovens.
    They come in 2 or three peices, slightly spaced apart, forming an oval surrounding a plastics piece that houses something (a coil?).

    They crack, causing sparks, and causing the inverter to fail. Then the plastic burns (smokes and chars).
    Why didn't the engineers point the fan to blow right on them?
    I'm assuming heat is the problem...

    Are these components available in aftermarket, or would you have to replace the entire power module?

    Are there any other real world applications for these Power Mudules?
    Are they used elsewhere besides Microwave Ovens?

    Should I be able to re-use the magnatron from these units? They look identical to other magnatrons that came from units with regular transformers.

    Just curious.

    The high voltage caps here are tan in color, and shaped like a rectangle, about 1" to 2" long, and 1" tall, with somewhat rounded edges. To discharge them I use a well insulated probe, and short out the two leads.
  5. #12


    Nov 30, 2010
    I'm not up to speed on the balun things (photos would help) but I feel a need to warn you that the power transformer and the magnetron are a matched pair. Do not put a 1000 watt transformer on a 600 watt magnetron or vise-versa.

    It would also be nice to use about a 1k resistor to discharge kilovolt capacitors. That will keep the surge current down to an amp or two. No need to stress the connections with a thousand amp surge!
  6. debe

    Well-Known Member

    Sep 21, 2010
    Sounds like you have a Panasonic Inverter type microwave oven. They are not what i would call a reliable oven & expensive to repair. The inverter powersuply is usualy what fails.