I have a roughneck petrol welder and I have no output on the welding side as well as no voltage output, the rheostat is ok as well as the static Board and slip ring brushes look good! Do I need to use a battery to excite the rotor windings? Windings measure ok I did find one diode D1 short circuit on the static board and replaced it but still have no output as well as no voltage on the 240volt socket out lets the power switch I checked and change according to the test I am performing, just wondering if anyone can help me?