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An SMD inductor fell of the board. It is marked L12. I have another working board and the are no markings on it, it's tiny and black. I touched the two points with a screwdriver for a second and the board LEDs lit up.
The device is an Extralis Vesda VLF-250.
How can I find what value to replace it with or is there a generic value to use?
I can't find a schematic.
Does anyone have a solution?
Most likely L12 is just a designator. It gives zero useful information about the characteristics of the inductor or ferrite bead unless you have the bill of materials for the particular circuit board in question. SMT inductors (except relatively large ones) are seldom marked.
If it's used as a filter (perhaps it is a ferrite bead), there are generic values that would probably work okay. If it's part of a switching power supply, replacing it randomly could well cause a lot of other damage.
A clear photo of the part and the general area of the PCB from which it was removed might allow more specific advice.
If it's L12 on the PCB, then impossible to tell the inductance. If you measure the size of it and compare to similar or identical ones, you can probably get a good estimation of saturation current capability of it and select a similar one.
To tell for sure, get yourself an LCR meter, unsolder the other one and measure the inductance. Choose one with same size and your chance of it not saturating and working should be high.
