I have found some capacitors like this one: General view


Does anyone know what kind of capacitor it is? How can I read its value?

  • \$\begingroup\$ Can I use this link to decode its value (I have been measuring some with my multimeter and the values some times are too different - maybe they are broken)? \$\endgroup\$ – Ucotecnico Nov 24 '15 at 20:27
  • \$\begingroup\$ How much are the values different when you measure them? Many capacitors have a much higher tolerance than resistors, and the values may seem very different than what is rated. \$\endgroup\$ – 3871968 Nov 24 '15 at 20:30
  • \$\begingroup\$ Is that ruler inch or cm? \$\endgroup\$ – PlasmaHH Nov 24 '15 at 20:44
  • \$\begingroup\$ Ucotechnio: try measuring it with your multimeter. \$\endgroup\$ – 3871968 Nov 24 '15 at 20:55
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    \$\begingroup\$ You're sure it's a capacitor? Back in my childhood I had a bunch of resistors that looked exactly like the ones shown in your photos. \$\endgroup\$ – Nils Pipenbrinck Nov 25 '15 at 0:48

These images appear to have your answer. This capacitor is a 0.01µF 250v capacitor from old electronic equipment (most likely radio, audio, or television related) containing vacuum tubes. It is similar looking to some of these which are old mica capacitors: enter image description here

The stripes on the capacitor can be interpreted using the standard resistor color code to give a 3-digit code like on standard capacitors, where the third digit is the multiplier. In order to read the capacitor code, simply multiply the number created by the first 2 digits by 10multiplier to get the final value in pF.

With resistors, the last stripe indicates the tolerance, but with older capacitors it indicates the voltage. If a tolerance is not specified, it is usually 20%.

enter image description here enter image description here enter image description here

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  • \$\begingroup\$ Unlikely. This is much smaller (7mm high) than the "liquorice allsort" capacitors, which were body dipped, and they are smaller than most vacuum tube era components. I'm curious where these came from - are they East European perhaps? HOWEVER the code may still be useful. I have seen silver-mica caps in a similar case style (but not marking). \$\endgroup\$ – Brian Drummond Nov 24 '15 at 20:51
  • \$\begingroup\$ It could be a 0.1 inch ruler. \$\endgroup\$ – 3871968 Nov 24 '15 at 20:55
  • \$\begingroup\$ I'm inclined to read it as 103 (10nf) 2%. \$\endgroup\$ – Brian Drummond Nov 24 '15 at 20:57
  • \$\begingroup\$ Brian Drummond: Usually if there is no tolerance band, it is 20%. Besides, there is no indicated tolerance value for a red band. \$\endgroup\$ – 3871968 Nov 24 '15 at 21:24
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    \$\begingroup\$ Maybe this chart is even better for old components: sphere.bc.ca/test/color-codes-oldohmandfaradchart.jpg \$\endgroup\$ – PlasmaHH Nov 25 '15 at 9:39

When electronic parts are marked with a color code, it is in floating point. Each color represents one digit value according to the standard color code. The first digits are the mantissa, and the last the power of 10 to multiply it by. For a small capacitor like that, the base unit is almost certainly pico-Farads.

One band will be different somehow. The number is read ending immediately before that band, which usually specifies a tolerance. These are less standard and therefore require knowing the manufacturer to know for sure.

You have BRN BLK ORN, so 1 0 3, which means 10 x 103. We presume pF, so 10,000 pF which means 10 nF in regular engineering notation. Again, the dotted red band could mean various things, like 20%, or a voltage range, or something. Without identifying the manufacturer and then finding the appropriate datasheet, you can't be sure.

For this size 10 nF cap, I'd expect maybe around 200 V capability.

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    \$\begingroup\$ Whoever downvoted this, please explain what you think is wrong. \$\endgroup\$ – Olin Lathrop Nov 24 '15 at 22:52
  • \$\begingroup\$ imo this is correct. \$\endgroup\$ – on8tom Nov 25 '15 at 0:22
  • \$\begingroup\$ Thank you for your answer. I have not idea about the relation between colour code and floating point. It is very useful. \$\endgroup\$ – Ucotecnico Nov 25 '15 at 7:32

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