XMT 300 - buzzing noise when turn contactor switch ON

[ctag]

I'll try to keep this simple... Picked up a XMT 300 for a good price. Got it hooked up on 230v/50a. Turns on no problem, and actually welds fine. The only concern i have is the buzzing sound it makes as soon as I flip the "Output (Contactor) switch to the ON position. Doesn't make a sound if that switch is off. Anyone have any insight on this issue? Thanks in advance

[ctag]

Heres a video to make things alittle easier.

https://www.youtube.com/watch?v=NlL5Q9wa5CE

[cruizer]

Quite normal for this unit

[ctag]

That seems to be the answer i've been getting. Good deal, Thanks for the response