I bought 2 of these 13A supplies off of the same person on ebay. I questioned about combining the shipping price for both and they said they could lower my ship price or throw in a extra power supply. I went for the extra power supply. The people were great and all 3 supplies work great. If you turn the voltage up to much it will shut off on you and the light will not come on. Even if you turn it down a little and plug it back in. You have to wait a little while for the caps do discharge or something. If nothing you try works I really believe just buy another one. These are a great deal. I use all 3 of mine several times a week for several hours at a time. If you exceed the amp rating it should just blow a fuse. Make sure you let it have decent air circulation during use. My opinion-just buy another from ebay its definately worth it!