pipeliner 200G ocv's are dropping

admin

four year old pipeliner 200 g even with the arc force knob on ten the ocv's should be at 98.and when you first start it they are .however without welding or anything the ocv's start dropping. they get down to around 91 or 92 within fifteen minutes or so.  the excitor output which starts at 130 also drops. it gets down to around 120 or so, doesn't weld great but welds alright. As the day gets hotter, they drop on down. gets so low that you can't hardly weld with it. won't burn a rod.Has gotten as low as 86. rpm's stay up at 1600 where they are suppose to be with the arc force knob at ten. have checked the excitor brushes, cleaned the excitor, checked all the main brushes and cleaned. any other ideas.