Back to Christmas time a month ago I bought a pack of two chinese Christmas kaleidoscope lights. They have a small slow rotation motor with a bubbled clear plastic wheel on the shaft and an aluminum PCB behind it with 3 high power LEDs (RGB) shooting through the wheel. Then the light go through the clear faceted spherical cover and creates a moving RGB pattern on the surface you project it to.
The Red LED on both lights soon failed. One right after I unpacked the light and turned it on, the second one failed in 3 nights. This was a quick weekend evening project to fix them.
The lights have a small constant current driver board inside with a 5W LED driver chip CL1221. The circuit is very simple and the load current is set by the resistor on pin 1:
The resistor value can be calculated from the formulas in the datasheet. The datasheet is in Chinese but I at some point found the English version but did not keep the link. Anyways, you basically just need the reference schematic and the formulas. The chip has two 4.7 Ohm resistors connected in parallel and connected to pin 1. That sets approximately 275mA load current (I figured the Np/Ns ratio of the transformer windings is ~5.2). The green and blue LEDs work OK with this current but the red LEDs failed.
The 3 LEDs are mounted on an aluminum board. To get access to the board I removed the wheel and a retaining washer that held it to the motor shaft. It was the LED1 that failed, I unsoldered it.
![Weekend project - Chinese kaleidoscope light 912560-2](https://www.eevblog.com/forum/index.php?action=dlattach;topic=226630.0;attach=912562;image)
I ordered a more beefy red LED from Digikey (350mA max current)
![Weekend project - Chinese kaleidoscope light 912564-3](https://www.eevblog.com/forum/index.php?action=dlattach;topic=226630.0;attach=912566;image)
It is a bit larger than the failed one but fits the PCB pads just fine.
![Weekend project - Chinese kaleidoscope light 912568-4](https://www.eevblog.com/forum/index.php?action=dlattach;topic=226630.0;attach=912570;image)
Soldered on the PCB, watching the proper polarity. The three LEDs are all connected in series. I also put a bit of thermal paste on the LED bottom.
![Weekend project - Chinese kaleidoscope light 912572-5](https://www.eevblog.com/forum/index.php?action=dlattach;topic=226630.0;attach=912574;image)
That did the trick and the lights are now ready for the next Christmas season.