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I have an older but quite valuable floor lamp, which I want to retrofit by replacing the fluorescent bulbs with LED bulbs, and by removing the ballast units. The floor lamp features four bulbs with 2G11 sockets and a special "dim" switch which allows to use either all four or only two of the bulbs. Now, I bought new LED bulbs which are suitable for connecting directly to mains voltage (type LEDVANCE DULUX LED L HF). My plan is to do the following:

  • Remove the ballast units
  • Renew the blub sockets (same type, but new)
  • Rewire (using Wago terminals) and mount the LED bulbs

However, I cannot figure out what the circuit diagram should look like. The installation instructions (EN)/(DE) of the LED lamps cover only the case for two bulbs, and of course no special "dim" switch. So, my question is what should the wiring look like?

Photo of the lamp

Circuit diagram (in place):
Circuit diagram (in place)

Circuit diagram (LEDVANCE manual, page 29): Circuit diagram (LEDVANCE manual)

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    Make sure to buy the right size Wagos. The ones for house wiring are too big for the wires in most lamps, and the ones for lamp manufacturing are not on the shelves in home improvement stores.
    – jay613
    Commented Feb 10 at 20:09
  • For the sake of completeness: This answer for a distantly related question points out dangerous wiring for a T5 LED replacement tube, but as far as I understand, this does only apply for rod-shaped lamps (being single- or double-ended) and not to U-shaped lamps as mine ...
    – Pontis
    Commented Feb 10 at 20:51
  • Your diagram looks fine, as long as you are removing the ballasts Commented Feb 11 at 4:41

2 Answers 2

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According to the answer from Ecnerwal, the rewiring should be as follows:

The dim switch controls power to the ballasts, so if you power the lamps from the ballast live and neutral connections (two per former ballast) as shown by the lamp diagram that should get the result you want.

Put into a circuit diagram, the solution should look like below. As far as I understand, the polarity does not matter, since the power plug (European Schuko socket) is not even protected against reverse polarity. Besides, the order of lamps could be changed to ensure symmetry if only two lamps are switched on.

Circuit diagram

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    Looks good but, since you have four lamps, and no longer have to worry about two ballasts, I would use a meter to determine how the switch acts on the a and b terminals, in order to see what interesting combinations of lamps I could get from that switch. It might be nothing, but it seems odd there are three wires from the switch to the ballasts, not two, and I wonder if the switch is more interesting than you know.
    – jay613
    Commented Feb 10 at 20:07
  • @jay613: Since center is off and assuming that the left positon powers 1a+2a, while the right position powers 1b and 2b, isn't using three wires the only way to achieve the "dim" effect by powering either only two or all four bulbs?
    – Pontis
    Commented Feb 10 at 20:38
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    Ah, yes. If that's how it works your diagram is good. Experiment with 3/1 bulbs instead of 2/2 for a dimmer dim. 25% or 100%. You might like that.
    – jay613
    Commented Feb 10 at 20:59
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The dim switch controls power to the ballasts, so if you power the lamps from the ballast live and neutral connections (two per former ballast) as shown by the lamp diagram that should get the result you want.

It appears that the switch has more wires connected to it than your diagram shows, (apparently they are there, but in a color so close to white I didn't see them) presumably the other direction is for all lamps on and the center is off?

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  • Regarding the switch: you mean in the photo? Actually, only five wires are connected to the switch – besides that, you are correct: center is off, left (A) powers only two lamps, right (B) powers all four lamps.
    – Pontis
    Commented Feb 10 at 15:40
  • I mean your diagram of the switch appeared to show only 3 of the 5 wires actually on the one in the photo, which is line to the middle contacts and one end to one ballast. Logically the other end of the switch has connections to both ballasts, but your diagram does not show that...Or perhaps does in a nearly invisible color.
    – Ecnerwal
    Commented Feb 10 at 15:57
  • Yeah, there are two gray lines. Sorry, I didn't think the color could be too bright!
    – Pontis
    Commented Feb 10 at 16:03
  • Thans, I created a circuit diagramm based on your answer. Would be great, if you could verify it. If it is correct, feel free to link the image in your answer!
    – Pontis
    Commented Feb 10 at 20:04
  • Looks right, & self-answering is perfectly fine here.
    – Ecnerwal
    Commented Feb 11 at 14:30

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