Sunbeam Mixmaster will only operatte on high speed.

SOURCE: Sunbeam Mixmaster mixer is smoking from the motor or the back are

you fried the motor it is not worth repairing

SOURCE: Regarding the Sunbeam Mixmaster (model

Pry the beater release button out with a screwdriver. There are two screws underneath it and one under the motor housing between the the beater holes. This will allow you to remove the chrome front cover, but not the motor and drive assembly. Getting to the part that contains the gears requires complete disassembly of the mixer. It is not designed for service, and requires patience and a variety of tools to disassemble.

It has a metal worm gear and plastic drive gears. If the beaters are out of alignment, then one or both of the plastic gears are stripped and the mixer is junk. Repair plus shipping costs equals the price of a new mixer. This is the weak point of these mixers and a fundamental flaw in an otherwise robust and sturdy design. It is definitly not the same mixer *********** bought 30 years ago.

SOURCE: Sunbeam Mixmaster Heritage Series Model 2350 speed problem

The speed control on the back is simply a variable resistance potentiometer, the same thing that controls the volume on older amplifiers. The output current to the motor is supplied by the printed circuit board in the bottom of the unit. This allows gradual increases in speed to avoid over-torquing the motor on speedup. Even the poshy-posh-posh mixers do this.

At least it still works. The most common problem is the cheap plastic drive gears that strip out with a mild cookie dough, this jams the beaters together and requires burial-at-dumpster.

SOURCE: Kitchenaid mixer professional motor

DO NOT DO IT. The Hz will destroy the morotr. The transofrmer only converts the voltage. You are better off buying a 220V version.

SOURCE: My Kitchenaid K5SS 300 watt standing mixer launches into the highest speed regardless of the speed ....

I would recommend that you first check the Hall effect sensor which determines the speed.  I had this exact problem (but mine occurred with a 600 professional model) and I actually went out and bought another Hall sensor for about $13.  I replaced the original sensor and made sure that the connection between the sensor and control board was nice and snug. My blender worked as good as new! But I was curious to know if my original sensor was defective so I put it back in mixer and again made sure all of the connections were tight.  Guess what?  My original sensor also made my mixer work!  There was nothing wrong with my original Hall effect sensor except the connection between the control board and sensor was not adequate--unfortunately I didn't check the connections before I decided to buy another one. My guess is that the connection between the control board and the sensor probably loosens or comes undone over time from use and vibrations. 
1.  Download the mixer parts and diagrams from the Kitchenaid website to see what the Hall effect sensor looks like. 2.  You'll need a phillips head screwdriver to open up the mixer. 3.  Make sure that the connection between the control board and sensor is absolutely tight and snug. 4.  Also, make sure that the orientation of the sensor connection between the control board and sensor is correct. it's hard to know which way the sensor should be connected because the control board has three prongs and the sensor can attach facing up or facing down. If, after you've made the connections, the mixer still doesn't work.  Disconnect the sensor and reconnect it with the prongs facing the opposite direction and try it.  I actually found the right orientation through trial and error.  By going through this trial and error, I also had my Eureka moment when I realized that the original sensor probably would also work it were reconnected with correct orientation.   5.  This whole process probably takes less than 10-15 minutes to perform.