The LED festoon must prove the bell board since 4 months in continuous use. The luminous efficiency is much better than the original lamps. Very bright white light, which requires a diaphragm or lens. I do not look directly at the chips anyway, very garish. Voltage level observed at 16V = is final, normally 12 V +/- 10%. My old bell transformer supplied unfortunately at 12V a voltage of 15V, so measure beforehand and use resistance.
