I've been helping my friend build a tailgate for his dump trailer and noticed that I don't seem to be getting full output on CV mode when using it with my feeder. So while he was welding I watched the voltage output with a multimeter and it was only making 22v with the knob all the way up (settings say 17-28v so should get 28 turned all the way up I assume). It measures 28v when there's no arc but as soon as an arc is struck it drops to about 22. I haven't tested with lower setting yet.

My first thought is to check the brushes. Anything else to check while I have it open?

Serial KK053142, STOCK NO. 500397-01-3