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enter image description here

I have been taking apart a old television circuit board and I found several of these things. They look like resistor but when I test them with the multimeter the resistance is very low, around 10 to 20 ohms.

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    \$\begingroup\$ Are they labeled on the PCB? R = resistor, L = inductor/ferrite bead, FB = ferrite bead. My guess (from the rounded shape) is that it's an inductor, but I could be wrong. \$\endgroup\$
    – jms
    Commented Sep 23, 2016 at 1:06
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    \$\begingroup\$ Yes, there is a L. \$\endgroup\$
    – Lucas
    Commented Sep 23, 2016 at 1:11
  • \$\begingroup\$ So if it is a inductor, what is its value? \$\endgroup\$
    – Lucas
    Commented Sep 23, 2016 at 1:24
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    \$\begingroup\$ about 3 cents :) \$\endgroup\$ Commented Sep 23, 2016 at 4:53

5 Answers 5

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That would be an inductor with a resistor style color code.

Here's a picture from that Wikipedia page showing some similar 100 µH axial lead inductors:

enter image description here Vahid alpha at English Wikipedia CC BY 3.0, via Wikimedia Commons

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    \$\begingroup\$ Didn't know they packed inductors into this shape. I always imagine them as unsightly spools of wire taking up space on the top sides of many PCBs. \$\endgroup\$ Commented Sep 23, 2016 at 16:11
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It seems very likely that it is a small-value inductor.

There is an open-source LCR meter available from dozens of vendors on Ebay for USD 15~20. Quite ingenious, dirt cheap, and excellent for identifying not only what a mystery component is, but also measuring all the key parameters. (Like inductance and series resistance for your inductor, for example.) Recommended for anyone who recycles electronic components.

Search for "Transistor Tester Diode Triode inductor Capacitance ESR Meter LCR" There are many to chose from.

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This is what a 10mH looks like. BRN-BLK-BLK

Since there are so many turns, it looks fat. The resistance determines how many mA can be passed thru with DC for filtering purposes in a low noise LC LPF supply.

http://www.digikey.com/product-search/en/inductors-coils-chokes/fixed-inductors/196627?k=&pkeyword=&pv7=3&pv19=90&FV=fff40003%2Cfff80013&mnonly=0&newproducts=0&ColumnSort=0&page=1&quantity=0&ptm=0&fid=0&pageSize=500

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That's a 10 μH inductor (brown-black-black = 10e0).

Low-value axial inductors of this sort are colored green to distinguish them from resistors.

With the increasingly common use of surface-mount technology, axial inductors (and resistors) aren't common in low-power circuits these days, except in some very cheaply made, hand-soldered devices where the factory doesn't have a pick-and-place machine (the stuff often associated with super-low-cost Chinese labor).

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Given that the colour bands appear to be
Brown Black Black = 1 0 x 10^0 = 10 Ohms then concluding that it MAY be a resistor may be a good guess.

However, it may also be an inductor or "choke".
If you are happy to destroy one, carefully scrape the outer layers off.
If it is an inductor it will probably have a ferrite bobbin core plus many turns of very fine wire.

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