I think I have one of those welders . It's square , gray has a low and high range and has a handle on top that makes about a half of a turn . If so use high range and follow the amp range for 7014 contact rod . High range will give you the longest duty cycle because you will be towards the lower amperage side of the dial . Keep the rods dry . As far as a setting for amperage goes . 1/8" probably maxes out at about
145 amps and minimum would be say 115 . You will have to adjust your heat to suit the thickness of material and type of joint . Outside corner would be less and inside fillet would be more . If the rod melts apart before it's used up or you burn thru the material then the amps are too high , If you have too hard of a time holding an arc or you get slag trapped in the weld then the amps are to low . If you have to turn the amps up so high to get penetration that the rod melts apart before it's finished then the rod diameter is too small . If you burn thru the metal even though the amps are so low that it's hard to keep an arc then the diameter of rod is too big .