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I’m struggling with six 11.5-watt LED cans wired in series. With a 75-watt incandescent at the end, the other five seem to function properly, though the incandescent is dull. With an LED in its place, it gets very bright and the other five LEDs get dull. And I can modify the intensity of the five LEDs by varying the wattage of the incandescent bulb. What’s going on here and more importantly, how do I fix it?

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    \$\begingroup\$ It's not quite certain what circuitry you're looking at, so please add a schematic. Also, this sounds like a simple series circuit problem? \$\endgroup\$ – Marcus Müller May 21 at 14:04
  • \$\begingroup\$ if your description is accurate, the different incandescent wattages represent different resistances, which limit the current given to the other LEDs \$\endgroup\$ – dandavis May 21 at 18:35
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Household lighting is not wired 'in series'. Ever. At least not if you expect it to work.

Each individual light fixture should be wired in parallel with all the others in the circuit so that they all 'see' the same voltage when the circuit is switched on.

schematic

simulate this circuit – Schematic created using CircuitLab

However, from your description, it seems that you have something like this:

schematic

simulate this circuit

You fix this by disconnecting your new LAMP6, reconnecting the switched hot back where it was before, and then connecting your new LAMP6 between this switched hot and neutral like all the others are.

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  • \$\begingroup\$ My apologies. It is parallel. Duh.... With reference to your diagram, the funky fixture is No. 1, that is it’ll be brighter than the rest, with No. 6 connected the same way as all the others. If I disconnect No. 1, No. 2 becomes brighter than the rest. Making the last fixture incandescent evens out LED intensity, but that hardly seems a solution. Thanks for the correction and suggestion though. \$\endgroup\$ – HCS May 21 at 20:05
  • \$\begingroup\$ So your #6 is probably in the Neutral line instead of the switched-hot line. Same solution applies. \$\endgroup\$ – brhans May 21 at 20:18

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