You may not be able to find separate F+ or F- leads coming out of small generators. Working on generators much smaller than 200 KW isn't something I generally do. However, I happen to own a 2000 watt generator made by Dayton and sold in the Graingers catalog. It was used for a project I built years ago and don't use much anymore. I checked that generator and here is what I found. The field part rotates and is energized by a set of brushes and slip rings. Power for the field comes from the stationary coils as does the output power. Since the field requires DC there's a diode bridge that rectifies the AC before it's sent to the brushes. In my generator the brushes can be gotten to, but I would have to dismount the diode bridge to determine which brush is plus and which is minus. I would then have to solder or carefully use clip leads to connect to the field. If you aren't sure just what you are doing, and aren't familiar with diode bridge rectifiers then the project most likely isn't something you would want to 'do it yourself.' Many 'do it yourself' projects require some level of knowledge and/or experience with simular technology to be successful. Many of the generators that I've worked on in the past used rotating rectifiers and are truely 'brushless'. The field leads coming out of the generator are, in fact, field leads for the generator's exciter, not the generator itself. I would assume that most small generators don't go to that extreme and just use a slip ring/brush setup. I would make that assumption unless your generator says 'brushless' somewhere on it. The big ones do. [links]