solenoid plunger binding or dirty
slide linkage to carb improperly adjusted--causing too long a stroke for plunger to bottom out in solenoid
if you don't have full 110 you will not have full weld
check your engine speed at high idle
check voltage at bullet nose brush holder studs--across the 2 at high idle you should read 110
check the taped connection behind the front panel (brown and black wires taped together with 3rd wire going to board)
check the condition of the rheostat
disconnect the blue wire from the rheostat and the brown wire from the taped connection-- across the 2 you should read 41 ohms.