Party light no longer bright

[Rebellelouch]

I hate the idea of throwing something like this away if I can fix it and use this opportunity to learn something.

I have a party light with three leds and a motor that isn't working right. The led are dim. I don't know much about electronics but I have a multimeter and a soldering iron. Thinking maybe a voltage regulator issue?

Issue is only with the LEDs. motor is turning fine. LEDs light up but very dim. Here are some pics. Any ideas if what to replace?

I appreciate any help in this. Thanks in advanced!

[stj]

the power supply is probably fine,
the leds are in series - if one fails it will effect the others.

it's an old design btw, the newer ones use 5 or 6 leds and a dc motor all in series.

[Rebellelouch]

Hmm.. wonder where I can scavenge a few of these multi colored leds. I'll try that first. That will be easy enough for my skill level. Can I use multimeter to determine which us out?

[stj]

read the voltage across each led.

[Rebellelouch]

Yeah.. I don't know what I'm doing.

I first reflowed solder all around just in case - no improvement

Took reading off red and black wires and getting something like 22v. Go to first led in series, same reading. Next led around 1v. Then the next led even less. No idea what this means.

Soldered red and black wires directly to the first led - no improvement

I notice before during and after all this testing nothing changed in the way the leds are acting. Upon turning on device leds are very dim almost off completely. They seem to brighten up over a short time but only slightly. Not enough to light up the device fully assembled.

I have to believe it is something on that board. There are two caps a transformer and some other smaller components.

Help! I just don't want to trash it.

[R_J]

That is a constant current led power supply. Looks like your problem is that the led's are bad. They seem to be 3v~3.5v 1 watt 350ma gullwing led's
This is one site that has them I believe, and there are likely a lot more
https://www.aliexpress.com/item/4000...E&gclsrc=aw.ds
Or here: https://www.aliexpress.com/item/3281...E&gclsrc=aw.ds

[Rebellelouch]

Thanks for the links. I ordered the leds. Needed 3 and got 30.. oh well.

[momaka]

LEDs tend to burn out like this: they get dimmer and dimmer until they no longer light up.

That doesn't necessarily means it's the LEDs fault. While it is possible that the LEDs are cheap quality, it is also possible that they are OK, but whoever designed the driver circuit is over-driving them to get extra brightness/"light output".

In the case of those cheap 12V flexible LED strips online, it's a little bit of both: the manufacturer often drives the LEDs in those strips right to their maximum ratings. And it doesn't help that the LEDs are cheap quality, so they could never actually sustain their light output ratings that their datasheet states. Case in point: I have a "12V" LED flexible strip that burned out almost completely (very dim LEDs) in just 2 months of 2-3 hours of use per day. Luckily, that strip had 3-in-1 chip LEDs, and only the one connected burned up. The other 2 didn't So I disconnected the burned branch and connected a new one that wasn't used before. But instead of feeding the LED strip 12V like I did before (and mind you, it was 12V to the dot, regulated), I connected them to a 9V power source. With this, the current dropped dramatically (as did the light output of the LEDs).... but I've been using this strip for same amount of time per day for the last 5 years now and my LEDs have not (visibly) lost any brightness.

So the moral of the story is: don't drive cheap LEDs near their maximum specs, and certainly don't over-drive them to get more light. If you want long life operation, drop the current to 1/3-1/4 and they should last a long time.

[Rebellelouch]

One strange thing to note, I bought it for my kids birthday party and used it just that once for a few hours. Packed it away and was like this the next time I took it out. 1 use and now practically trash.

[Rebellelouch]

UPDATE: LEDs came yesterday. I installed 3 new ones and they are working at full power!(had to redo it after realizing they had +/- designations and I had two backwards). Thanks for the tips. Saved this guy from the trash can.

[momaka]

Nice! Glad to hear it's working properly again.

Also, thanks for coming back and reporting on your fix!

[sam_sam_sam]

Did you measure the current on this device to see if the LEDs are being over current

Because this might have caused this problem in the first place