Hello everybody. I just purchased a new Dynasty 200 DX TIG welder after having used one at a "Demo day" at my local welding store. When powered up, the machine makes a fairly loud humming sound that I did not notice on the demo machine. When powered down, the humming kind of winds down slowly rather than instantly going away. It is there no matter what setting the machine is on, but it does go away after starting an arc in the DC setting. I also own a Maxstar 150SL and that machine does not make this sound. The machine welds fine, but I'm wondering if this is normal or not. My first thought was that there was something wrong with the cooling fan, but it's not the fan. The fan kicks on and off normally.

Any input is greatly appreciated!