Check with the manufacturer to see if they can explain it. Sometimes when chemical type lamps get too hot they will do a color shift. Or perhaps they are simply defective (i.e. contaminated). Are you having less than rated life problems? If so, they are likely to be defective.

ya i think u are right. it may be a problem with the control gear.actually ita a metal halide lamp in sodium gear o same rating i.e. 400 W.but i think their should not be a problem.what do you think?

Again, ask the manufacturer. The transformers and controls and other features are specifically designed for one type of lamp operation, and will have strange anomalies when different lamps are attempted.

Regards, CJM

ok i"ll that thanks for everything.

I'd check for higher voltage than the lamps were designed for.

Your lamp is running on holding current. The control gear is not supplying sufficient current to reach it the full glow. It is controll gear (CG) which is doing the mischeif.

Alternately voltage supply might be resposible for this situation. But then the starting of lamp will become hard if igniter is being used. Check supply voltage it should not be less than 6% of the rating. If voltage is okey then change the CG.

ya i think you are absolutely right, i"ll check and share the experience after rectification of the problem.thanks for such a warm response, thank you all.

Make sure that the lamp matches the ballast this is very important, unlike high pressure sodium witch will cycle on and off because of temperature rating.