How do I connect a fluorescent lamp with capacitors (or capacitor+starter?) and a ballast?

picture of the circuit

I made a diagram to make it clearer. lamppu = lamp and katto=ceiling.


I need to know where to connect these three cables that are loose from the capacitors and ballast.

migrated from electronics.stackexchange.com Feb 9 '18 at 12:12


  • What is that lamppu? A bare four-terminal fluorescent ("neon") tube? Or a two-terminal tube with integrated starter? Or does it have electronics? What does its manual say? – Janka Feb 9 '18 at 11:04
  • Thanks Janka! Lamppu is LAMP in finnish. Its a fluorescent lamp, without (i believe) an integrated starter. The lamp reads radium ralux duo 26w/827 - something like this: radium.de/en/products/… . it was bought second hand, and no manual in it. – Julia Feb 9 '18 at 11:36

There are many ways of arranging a fluorescent tube circuit, one of the oldest ones is like this:


Pre-heat Fluorescent tube circuit

A: Fluorescent Tube B: Power (+220 Volts) C: Starter D: Switch (Bi-metallic thermostat) E: Capacitor F: Filaments G: Ballast

Another is like this


Semi-Resonant Fluorescent tube circuit

There are other arrangements - see Wikipedia

  • OP's fluorescent bulb is a 2-pin CFL. I gather the twin-and-earth exiting to the right is to the lamp proper. – Harper Feb 10 '18 at 4:31
  • @harper Yes. Lamppu means lamp. I am still puzzled as i have a 2pin lamp (not a tube), and my ballast has only 2 cables. Added to that i am quite a dummy in reading those diagrams. – Julia Feb 10 '18 at 5:14
  • So as i understand the second wire of the ballast goes to the bottom connector together with the neutral wire of the lamp. And the capacitor+starter loose wires go to the live wire of the lamp. Does that sound right? then i can connect the ceiling live to lamp live and ceiling neutral to lamp neutral. Same with ground. – Julia Feb 10 '18 at 5:22
  • @Julia no, that would just be putting everything in parallel. Placing the ballast in parallel with the lamp makes no sense. Placing power in parallel with the lamp makes no sense (that would simply be direct feeding power onto the lamp). Nothing goes to the earth terminal except green/yellow wires. There's a 4th set of terminals on there for a reason, it must surely be used to place things in a different arrangement. – Harper Feb 10 '18 at 5:54
  • 1
    Thanks for the explanation! I ended up just changing the socket and going for a new lamp. :/ – Julia Feb 10 '18 at 12:28

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