I bought 2 years ago a mig welder that also can weld as a mma. i can´t weld properly with it ,because it melts the wire but not the work piece . An eletronic repair man saw the welder and said that the control board doesn´t produce pulse (he said that the welder doesn´t change the frequency) for the welder to melt also the work piece. I check the welder and it has voltage on the output. the display voltage and display amperameter don´t change if i twist the potenciometer (also check the potenciometer and there is a small change in resistance). My question is can the welder melt the wire without changing the voltage? i did a video where with a amperemeter clamp i can see the amperage on the welder and saw also the voltage that is gone from 51v to 23 volts. Can anyone help me out here so i can figure out how an inverter welder works?