I purchased this item for a DVD Player for my car.  It was advertised to have various tips so it would fit most any component and also had voltage settings.  Some of the reviews talk about blowing fuses and would not work.  Well the reason for the problems is the tip has to be installed properly.  If it is installed backward it creates a direct ground. That blows a fuse.  The center pin has to be positive and the outside has to be negative.  It is not marked so I used a volt meter to assure which was which.  It works great.