need help with lincoln 250 idealarc welder

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hello, i just bought a old lincoln model 250-250 ac/dc stick welder.  got it home and hooked it up i don't understand the setting for the dc- and dc+ and straight ac i was wondering if anyone could tell me what settings i should use these for andwhen i should use the dc- and dc+ i have never had a ac/dc welder before thanks for any help.
Reply:Copy the exact model and serial off your machine and see if you can download a owners manual off the Lincoln site.  Also there is lots of educational material.  Electrode positive or reverse polarity is most common and can be used for any electrode I can think of.  It would be easy to just use that arrangement most of the time.  Electrode negative or straight polarity is nice for E 7014 and E 7024  AC is a good choice when you develop arc blow on DC.  For a beginner don't worry about it until the arc wanders around for some unkown reason.   This usually happens when welding into corners where magnetic fields are developed by the flow of welding current.
Reply:+ and - polarities have to do with which direction the electrons are flowing. as basic science states electrons flow from positive to negative. so when you're using electrode positive your electrons are flowing from the work piece to the electrode. with electrode negative your electrons are going from the electrode to the base metal and it is a much more violent arc and the electrons actually perform a sandblasting like function because they are moving so fast from the torch to the base metal the it's like a sandblaster, it is generally much more difficult to weld with electrode - then with +. ac stand for alternating current which is when the machine switches from dc + to - about 60 times a second. ac is generally used for aluminium because it has the cleaning action of electrode - but the more stable arc of electrode +.
Reply:thanks guys for all the help.