Please be careful when working with a ballast.

Some ballasts have huge ass capacitors in them.

A capacitor can hold a lethal charge even when the power is disconnected!

ALWAYS make sure any capacitors are discharged before working with your ballast. If you are unsure what this means, or how to do this safely, please contact a professional.

Please read this safety guide for more information.

Sci.Electronics.Repair FAQ: Safety Guidelines for High Voltage and/or Line Powered Equipment
Hempfester Reviewed by Hempfester on . help with this ballast please i have this old ballast, i'm not sure if it's mh or hps, the guy i got it from said he thought maybe it was a mercury vapor, i'm hoping not though... it's a white box with a big loop bold coming out of one side and a large socket coming out of the other, i took it apart and can see that it was originally 277v, but it has wires to switch to 208 and 120v. someone has already rewired it for 120. there's a sticker on the inside saying hpf, 400w, it also says ruud lighting. i'll upload pics soon as Rating: 5