Newbie level 3
I have an inverter TIG welder that all of a sudden started working at maximum current. Tried using it and burn a hole right through a 1/8" piece of aluminum and my welding table . None of the controls affect it. It's about 20 years old and has analog circuitry to generate the PWM. The pin on the board driving the IGBT has obviously gotten hot but I've tested most of the components and they seem to be OK. Is it common for IGBT's to permanently latch when they fail? Could this also cause high current through the gate causing the burnt spot around the pin to the IGBTs? The IGBT's are down in the bottom of the unit and I have to take the whole machine apart to get at it so I have not been able to identify the specific IGBT's or the layout. The machine is an Italian FIMER unit and the schematics are not available. Any ideas if I am on the right track?