as far for exploing MH lights there is something wrong with that main thing is check the ballast to make sure it show what wattage it can run and check the capaitor to make sure it is not shorted ( shorted will dim the light ) and do not over tighten the bulb in socket and many time it can have small fracture and it will bulid alot of pressure i know 400 watts mh (probe type) arc tube can go high as 50 psi !!! that why becarefull when tighten it down and check the ballast voltage and current drawage and sometime i use "shorting test" that mean actally short the lamp lead not cord end just lamp and get amp meter to check the current drawage to make sure it is not too high

merci marc

p.s. if need more help just post it here i will try to help you with trobleshooting i work alot of this one

Pas de problme,il marche n'est-ce pas?"(No problem, it works doesn't it?)