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This is related to a separate question I posted here: LED chandelier lights permanently dim.

I have an LED chandelier that it appears that I need to replace my transformer in as per the comments in my above post. I have almost zero electrical knowledge, at least in any practical sense, so I'm not sure how to interpret the numbers on my existing transformer in order to select a new transformer. Also, I'm not sure where the best place to get a new transformer might be. I'll start with Amazon.com but if anyone has suggestions it would be appreciated.

Here is a picture of the existing transformer.

enter image description here enter image description here

Also, there is a copper wire coming from both the lighting fixture as well as the wiring coming from my ceiling. I understand that this is the ground wire. They were not connected when I pulled the light off. Is this a problem? Must they be connected? My understanding is that they would connect via the mounting plate.

Update

Considering this transformer. It shows not quite 12v on the output and it also shows 5amp. Is that a problem?

enter image description here

This looks like another alternative (my understanding is since this is 60w @ 12v that means it is 5amp, right?)

enter image description here

Both of these also say "For use with halogen lights only". I'm running LEDs, but does it matter since the output is "right"?

  • This looks like an oldschool (is, heavy not electronic) transformer. Usual failure mode is overheating which blows the internal thermal fuse. But this shuts down the light completely. If your lights are dim and not completely off, and this is really a magnetic transformer, then I'd recommend checking all the contacts and wire nuts before replacing it. – bobflux Oct 11 at 16:05
  • Also do you need a flicker-free and/or dimmable solution? – bobflux Oct 11 at 16:06
  • @bobflux, dimmable would be nice but currently my switch is a non-dimming switch. I'd have to swap it out. I'm not sure what you mean by flicker-free, because flickering doesn't sound like something anyone would want so that leads me to believe I don't understand your question. – Ryan Griffith Oct 11 at 16:37
  • Note that with an LED fixture that is designed for an AC power supply, you probably won't be able to get dimming as a feature. There are dimmable power supplies for LEDs, but these are designed to drive the LEDs directly with modulated DC voltage, which probably won't work well with an LED fixture expecting AC. You can get "dimmable" AC power supplies, but these are just changing voltage, not duty-cycling the LEDs at high frequency the way a real LED driver would. – Peter Duniho Oct 11 at 19:40
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    Both should work, the more powerful one is cheaper and more convenient to mount so I'd go with this one. Make sure it fits inside the fixture... – bobflux Oct 13 at 8:26
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I'm not sure how to interpret the numbers on my existing transformer in order to select a new transformer.

You just want to match the numbers. It's not that important to understand what they mean. That said, note that the output is 12VAC (AC is "alternating current"). LED drivers are usually DC ("direct current"), but there's this corner of the market that seem to be descendants of the landscape lighting market and low-voltage incandescent lighting market, both of which use AC.

Which means you might have better success finding a replacement transformer by looking for landscape or low-voltage incandescent lighting parts, rather than "LED driver" parts.

So, find a transformer that meets the following:

  • 120 volts AC for input (i.e. normal North American household line voltage)
  • 12 volts AC for output
  • 4 amps (or as the markings show, 4000 mA...same thing) current for output

Be very careful about the output AC vs DC, because this is where you'll likely find the most confusion, since there are those two different styles that otherwise seem very similar.

If you find a transformer rated at higher than 4A, that's fine. You just don't want less. You should try to get 4A or as close to as you can though.

there is a copper wire coming from both the lighting fixture as well as the wiring coming from my ceiling. I understand that this is the ground wire. They were not connected when I pulled the light off. Is this a problem? Must they be connected?

There's a green screw on the ceiling plate, which is intended to be a ground connection. Judging from the bends in the wires in the photos, it looks like the original installer tried to connect the ground wire from the supply cable along with the ground wire from the lamp cover to that single screw. This might even be the way the lamp was intended to be installed, and the wires might even have been connected there at some point, but getting two different wires secured to the same screw like that is difficult.

You would probably have better luck getting a screw nut and a short piece of extra wire (preferably the same size as the supply cable wire, though since they used a smaller wire for the lamp cover anyway, I'd say the size isn't too critical). Use the wire nut to secure all three wires together — the supply ground, the cover plate ground, and the new wire — and then secure the single new wire to the green screw in the ceiling plate. You'll need to straighten out the ground wire from the supply cable.

And yes, it's a good idea to make sure the ground connections are done.

As far as finding specific suppliers, that's technically outside the scope of the Stack Exchange network, including this site. But if you search for "landscape lighting transformer" with your favorite web search engine, you're likely to find a variety of vendors that could be useful. Alternatively, look for parts for low-voltage halogen lighting. These are often used for decorative lighting, cabinets, or track lighting.

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  • I have done some searching and have found a transformer that indicates 5amp and 11.7v. Does the concept of "close enough" work here with volts or will this cause issues? Please see my above update as it has a photo of the transformer I've found that seems like it might be compatible. – Ryan Griffith Oct 11 at 13:59
  • @RyanGriffith: that transformer might work, but you won't get ideal results. With a halogen fixture that the transformer is meant to work with, the 2.5% voltage loss would result in only a little loss of brightness. But LEDs are designed to work exactly at a specific voltage and their brightness drops off quickly, in a non-linear fashion, when the voltage is reduced. 11.7V is probably close enough that the LED bulbs would still work, but it is likely that they would be significantly dimmer. – Peter Duniho Oct 11 at 17:06
  • Peter, what about the second transformer I listed right at 12v? It still says "Halogen" but it has 12v output. – Ryan Griffith Oct 11 at 17:08
  • I'm not sure about the second one. As far as the power goes: it lists the output as watts instead of VA, but VA load will always be higher than watts (power factor is always less than 1.0), so the 60W output implies a VA rating of over 60VA, which is higher than the 48VA needed. The problem is that it's apparently a switching power supply with a frequency of ">20kHz". It might work, but the previous transformer is probably a regular magnetic transformer with output frequency identical to input (60Hz in the US). The difference could be incompatible with the LEDs, depending on design. – Peter Duniho Oct 11 at 17:21
  • all of these details are just making me think that it isn't as easy as just matching up the numbers from the old transformer to the new one. There seems to be all these details beyond just the numbers printed on the device. Any guidance on getting to a solution here would be appreciated. – Ryan Griffith Oct 11 at 17:50

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