Ordinary lamps (non-halogen) subject to wear. They are replaced about once every 2 years, even if they haven't burned out yet. An incandescent lamp with reduced brightness is identified by black deposits on the glass bulb.
Before replacing a burned-out lamp, switch off the corresponding consumer.
Caution: Do not handle the lamp glass with bare hands. Fingerprints darken the lamp and deposit on the reflector due to the heat. Be sure to replace the lamp only with a lamp of the same rating. If there are stains on the lamp glass, remove them with a cloth soaked in alcohol.