HID-system   conditions Lamp does not start. Other than lamp Ballast failure Incorrect or loose wiring Low supply voltage Low ambient temperature Circuit breakers tripped Inoperative photocell Starting-aid failure (HPS) Lamp Lamp loose in socket Improper lamp wattage Normal end of life Lamp internal structure broken Lamp cycle is on and off or is unstable. Low supply voltage Normal end of life (HPS) Incorrect ballast Lamp operating voltage too high High supply voltage (HPS) (HPS) Ballast voltage low Lamp arc tube unstable System voltage dipping Fixture  concentrating  energy  on  lamp (HPS) Lamp is extra bright. Shorted or partially shortedballast or Improper lamp wattage capacitor High lamp voltage Overwattage operation Lamp  is  dim. Low supply voltage Incorrect ballast Low ballast voltage   to lamp Dirt accumulation Ballast capacitor shorted Corroded connection in fixture Improper lamp wattage Low lamp voltage Lamp difficult to start FIXTURES There  are  fixture  configurations  to  meet  almost  any lighting  requirement  or  design.  While  the  basic  purpose of the fixture is to hold and prevent damage to the lamps and lamp sockets, the fixture also helps direct the light beams into the lighting patterns desired. The fixture, with  its  reflector  and  lens,  determines  the  quality  of  the light being produced. Reflectors can either concentrate or diffuse light rays, and the lens can pass or refract light rays.  Quite often, the lens may be used to do both from one light source; that is, part of the light rays are refracted to produce a soft, even spread of light in the outer part, while the light rays are concentrated in other areas of the lens to produce a bright, hard light at a specific area. Some streetlight fixtures are examples of this. The sides of the lenses produce a general diffused lighting to prevent blinding automobile operators and, at the same time, they produce a bright light pattern below the lamp along the curb. Flood or security lighting fixtures may be either open  or  enclosed.  The  open  fixtures  provide  higher maintained efficiency and more accurate beam control. The open fixture will, under some conditions, require a “hard glass” bulb to prevent bulb breakage. Most fixtures will have provisions for mounting ballasts (transformers) within the fixture and will provide  protection  for  the  ballast.  In  some  cases, particularly in light pole lighting, the ballasts may be mounted in the pole base and not mounted in the fixture. Several methods of fixture attachment are possible and should be considered when fixtures for a particular job are  ordered  The  location  and  job  determine  whether  the fixture   is   suspended,   bracket-mounted,   or   arm- mounted.  Most  brackets  can  be  attached  either  to  wood 6-16