Ballast match wattage?

Hello I am going to buy a lamp off of a friend and he has a 400 w hps/mh convertible light however, he told me he is running them on a 1000w ballast is that alright to use a higher wattage ballast with a smaller watt bulb?
thanks for the advice

No i am no electrician but i would not risk it run the light of the ballast made for it.How much are you paying for them because there is a nice little shop i have just come across called the kit bag shop.Got tent 600 hps exaust fan for 250 the tent is worth that alone.Go on e bay and get one of there you can pick one up for about 40 50 pound,or buy your friends and take the risk.

yeah dude dont risk it, that shit can get really messy eh, like tyke said just get one off the net for next to nothing.