I have some LED modules powered with 12 VDC. Each module has 3 LEDs and 3 resistors all in series. After working for one year, in some modules, one or two LEDs turned off but another one is on.
I wonder because all LEDs are series and must conduct current because one or two led are on but one or two are off.
Why does this happen?
I choose three 27ohm resistors for sinking 30ma current if LEDs fail in a "short" mode, why when I increase input voltage, the off LEDs become on?