Lamps may be leaking in air, due to tiny cracks in the ends of lamp glass caused by shipping abuse. Replace lamps.
Sockets may be dirty or worn out. Check, clean or replace if needed.
Lamps may not be properly seated in sockets. Check that pins or lamp ends are properly seated in sockets.
Ballasts may have reached end-of-life, or may be defective. Change ballasts where needed. Typically in American beds, each ballast powers two lamps; in European beds, the ratio is one-to-one, except electronic ballast.
Not tanning—bulb wall (outside of lamp glass) temperature should be 105 degrees Fahrenheit or 40C. In poorly cooled lamps, the bulb wall temperature is often as high as 130 degrees Fahrenheit. This reduces the lamp’s output to only 65-70% of rated output. Vacuum out bed, blowers and clean the fan blades to permit better air circulation.
Slow tanning/not tanning—old acrylics may be filtering out a significant amount of ultraviolet. Using a U.V. meter, check the output through a new acrylic and again through the old acrylic. If a significant difference is noted, replace the old acrylic.
High output resulting in erythema or reddening—check to be sure that the lamp is the correct one for the bed or booth in question.
Short life-see “Appearance”—see item f in “Appearance.”