Christmas light transformer replacement

Forums › Gadgets, robotics, home automation, electronics (including wearables) › Christmas light transformer replacement - needs 36v / 8w

boland

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#311150 18-Dec-2023 12:25

Yesterday evening on of our christmas lights went out, turns out that the transformer is broken. I've tried with a different transformer, and then the lights work, albeit much dimmer.
It connects via a round 2 pin plug to the lights, which seems a pretty standard connector for christmas/LED lights

The broken transformer is 36v / 8.8w. I can't find a replacement here in NZ, and on Aliexpress most are 31v / 6w.

The mrs also would like to have it fixed before Christmas, so Aliexpress isn't a good option.

Any suggestions what I could do? As it's just a transformer, wouldn't I be able to use any 36v transformer & just cut off the plug & connect the wires directly? I can't find a 36v transformer here though, not even at Jaycar.

richms

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#3172987 18-Dec-2023 12:43

Most of them are not transformers, but a current limited DC supply so you have to match the voltage and current to the set. Many sets now just have 10 to 12 LEDs in series and then all in parallel off the power supply so if you use a wrong current limit one it will cook the LEDs, the old thing of getting one with more current than the load doesnt apply with bare LEDs like other loads.

Richard rich.ms

boland

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#3172997 18-Dec-2023 13:14

richms:

Most of them are not transformers, but a current limited DC supply so you have to match the voltage and current to the set. Many sets now just have 10 to 12 LEDs in series and then all in parallel off the power supply so if you use a wrong current limit one it will cook the LEDs, the old thing of getting one with more current than the load doesnt apply with bare LEDs like other loads.

Ah thanks! I've read about current limited DC supply but I had no idea what it meant, now I do :)

So getting a transformer isn't going to fly.

Guess then my only options is to get one from Aliexpress? The closest I could find is 36V @ 6.9W; the one I have now is 36v @ 8.4W. So guess they will light a bit dimmer.

CokemonZ

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#3173020 18-Dec-2023 14:21

I am in the same boat, had a few go walkies. Am waiting on an adjustable power supply. So that may not work?

hairy1

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#3173021 18-Dec-2023 14:22

Can you post a pic of the broken one? I have a couple here left over from old sets that may fit that you can have if they fit

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boland

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#3173195 18-Dec-2023 18:06

hairy1: Can you post a pic of the broken one? I have a couple here left over from old sets that may fit that you can have if they fit

Thanks!

See photos

hairy1

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#3173225 18-Dec-2023 21:18

Hmmm. Someone with more knowledge of how these work than me might be able to tell if this will work as it's lower voltage and wattage but happy for you to have it for postage only.

Where do you live @boland I am in Pukekohe.

Cheers.

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pureinception

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#3173230 18-Dec-2023 21:32

How much did the lights cost? You may find that a power supply here will cost the same if not more than buying a new set of lights. If you are handy you could open up the transformer, they are clipped together so can be pryed open and inspect it. Usually it will be a capacitor that has blown which you should be able to find at Jaycar and solder in.

boland

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#3173442 19-Dec-2023 15:36

hairy1:

Hmmm. Someone with more knowledge of how these work than me might be able to tell if this will work as it's lower voltage and wattage but happy for you to have it for postage only.

Where do you live @boland I am in Pukekohe.

Cheers.

Thanks @hairy1, but I already tried a similar specced and then the light output is quite low. Thanks for the offer though.

I tried to pry it open, but no luck.

Bung

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#3173448 19-Dec-2023 15:54

Are you sure it was that similar? 31v v's 36v 7w v's 8w doesn't seem far enough apart to produce a markedly different result.

pureinception

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#3173450 19-Dec-2023 15:54

I tried to pry it open, but no luck.

Take a look at this: https://www.youtube.com/watch?v=5EsnrO45ObA.

Or this: https://www.youtube.com/watch?v=NQNmCjj3TkQ that has the multifunction controller

boland

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#3173453 19-Dec-2023 16:12

Bung: Are you sure it was that similar? 31v v's 36v 7w v's 8w doesn't seem far enough apart to produce a markedly different result.

I tried with a 31v 6w and it was noticeably less bright than the old one.