Airco 300 Heliwelder IV Blown circuit board component

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PicturesMy welder started to weld as if my current dial was set to 0 at all times.Upon examining the circuit board i found 1 transformer that blew up. I circled it in the picture. Unfortunately the label side of the transformer is the side that blew off. I do not know what exactly the thing is. There is another similar looking transformer with part number PN3645. My initial hunch is to just replace the blown one with the same type located near it on the board. However the back side of the 2 parts are slightly different. The one still on the board has a completely round back with color bands (yellow, red, orange) from top to bottom. the one i removed is only partially round on the very bottom then it's cut away to a flat surface. So if they are the same part they came from different manufacturers. Which is possible but not probable. I'm hoping someone has a schematic of this circuit board and can tell me exactly what my bad part is.