LD20 inductor replacement

[Dietz]

I have here an LD20 that was dropped from a certain height and stopped working. I took the guts out and found the problem, a tiny inductor has broken free and one end of it's microscopic copper wire has severed.

Does anybody have any idea if that inductor can be bought somewhere to unsolder the leftovers and resolder a new one?

Thanks for your help.

 

[datiLED]

You can definitely get an inductor like that at Mouser or other electronics supplier. Ideally, you would find the value on top of the existing inductor, or measure the inductance with a meter. Without that information, it would be an educated guess for the value. It is likely between 2.2uH and 10uH, with 4.7uH being my first guess.

Once you decide on a value, sort the inductors by size (to match the original). Pick one with a low DCR for good performance. You don't need ultra low DCR, but keep it well under 0.5 Ohm.

Clean the existing solder from the pad and use fresh solder paste, or solder to install the new one. After testing, add a bit of hot glue or epoxy around the inductor to prevent it from happening again.

 

[Dietz]

Well, believe it or not, I was able to tin the broken ends of the microscopic copper wire. I took off the remaining ferrite bits from the solder pads, put some nice leaded solder, and was able to solder the tiny wire bits to the pads. There is good conductivity between the two pads through the inductor. Before it was completely severed.

But... the light still isn't working. It's still displaying the same symptoms (when I click it on, the led faintly blinks on for a split of a second then shuts off, not matter which mode or position it's at) Either the inductor is too damaged, or something else must be damaged that I can't see. The other much bigger inductor is a little cracked at the ears, but it's not sheared off like the tiny one was, and it has good conductivity too. Something else that I can't see must be damaged. I think.

Maybe a bigger capacitor hidden in the middle, or a transistor.

I don't know enough about this stuff to properly diagnose it, and my multimeter doesn't test inductance so that doesn't help lol. I'm not sure why it's behaving exactly the same now that I've reconnected the inductor, as it was doing before when it was completely severed off.

There is no value written on the intact side, it must have been written on the soldering side (there seems to be some very faint white marking left, unreadable now of course).