If you are using a dimmable ballast, tell me youre using a 400w bulb and not using a 600w bulbimmed down to 400w. The balladt is not meant for that. It REALLY overworks the ballast and sometimes if the duty cycle is different it can literally shake the inside of the bulb apart. Or what usually happens is nothing, nothing at all. Until the fire. So please tell me that you use a 400w bulb when the ballast is dimmed to 400Yes Ive had some problems. I bought two of their 600w HPS One I used immediately the other had to wait until new seeds arrived which took a month. Hooked the 2nd one up and the ballast died after 5 days. It was over 30 days (Amazon Warranty) but they gave me a one-time over warranty return. I reordered another same day. The replacement works fine so far and the first light works excellent also but the ballast has gone to whining loudly but otherwise working fine but since plants are in veg Im only using 400 watts. Im concerned the whining may be a warning. I contacted Vovosun directly and they replied wanting the invoice number just waiting to see it they think it is an issue and will do anything about it. The whining doesnt bother me since its in a dedicated grow room I just hope it doesnt go out. Other than that they are kickass lights for the money.