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I am working on an electric fence energiser and trying to figure out what the issue is. I am testing all of the components and have taken these capacitors out of circuit to measure them. I am unsure what J signifies though as the readings I get on a multimeter don’t seem to align with uf, nf, pf etc when I put it into a conversion page. To be able to replace them with the same value I need to work out what value j is.

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  • \$\begingroup\$ how do you know that the component is a capacitor? \$\endgroup\$ Commented Dec 9, 2022 at 22:53
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    \$\begingroup\$ From the look of them and the fact all fencers have them. Plus they give you one hell of a shock when they work. \$\endgroup\$ Commented Dec 9, 2022 at 23:11
  • \$\begingroup\$ What readings do you get with your multimeter? Do they have the same digits as on the components (22 or 11)? What conversion are you trying to do? \$\endgroup\$ Commented Dec 9, 2022 at 23:53
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    \$\begingroup\$ @Barry well the one rated 1j 400 reads 1.033uf the one rated 2.2j 250 reads 50.25nf so presume that’s shot. \$\endgroup\$ Commented Dec 10, 2022 at 20:22

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On a capacitor, J usually signifies that it has a 5% tolerance: -

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So, when the capacitor marking is 2.2 J 250 it usually means 2.2 μF rated with a 5% tolerance capable of withstanding up to 250 volts. To be clear about whether the 250 volts is DC or AC depends on knowledge of the capacitor type.

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  • \$\begingroup\$ So on my capacitors it would be 1.1Uf 5% 250v and 2.2Uf 5% 400v ? \$\endgroup\$ Commented Dec 9, 2022 at 23:10
  • \$\begingroup\$ @IainSimpson Most likely. For some reason capacitors are always either marked in μF or pF, never nF or mF, and these are too big to be pF. \$\endgroup\$ Commented Dec 10, 2022 at 0:40
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    \$\begingroup\$ @IainSimpson you have a 1 uF 400 volt capacitor. \$\endgroup\$ Commented Dec 10, 2022 at 11:03
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J means the capacitance has a 5% tolerance.

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