Some of the mixers have common connectors.

It appears that for the three pin connector, pin 2 is center tap of AC source, and pins 1 and 3 are the ends of the transformer windings.

This is from a schematic of a MX2643A which MAY be similar to yours. One of mine has a 3 pin Amphenol connector with a locking screw ring...

Use this info at your own risk, however, the power inout is easy to trace out to verify. They use a typical bridge rectifier to get plus and minus from the external transformer.

The pin markings on the connector CAN be confusing.

Suggest you use the light bulb trick of putting a small lamp in series with the 120 line as an auto reseting fuse.