My brothers Kitchenaid mixer got knocked off the counter and the cord ripped out. He hooked the cord back up and now it runs backwards so he reversed the cord and it still runs backwards. The motor does have brushes. Anyone got an idea what's going on and how to fix it? Thanks Karl
Of course reversing the cord won't make a difference. The cord is a two-pin plug isn't it? Is it even new enough to have the wider pin to polarize it? Anyway -- it is AC coming from the wall, so it is revering the power sixty times a second (in the US -- fifty times in the UK) anyway.
It is probably series connected -- one side of the line to one of the brushes, through the rotor, and out the other brush, then though the stator winding.
Reversing either the brush connections or the stator wiring (but not both at the same time) will change the direction of operation.
Probably one end of the stator is connected to one of the brush holders, and the brush holders got interchanged in the excitement. Open it again up and try to swap positions on the brush holders.
I repurposed an old Kitchenaid mixer which indeed used a universal motor such as that. I ended up having to reverse it for the application I needed (driving a solenoid winder), which, while straightforward, was still a rather tedious job.
I wonder how OPs ended up reversing itself due to mechanical shock.
If the brush holder moves, it could have gotten knocked into a position where the motor is reversed. Have a couple of universal motors where the reversing is done that way instead of electrically switching brushes or field windings. Actually is a better method since it cuts down on brush arcing when running in reverse. One these motors, the brush holders are mounted in a ring around the commutator and the ring rotates about 90 degrees for reversing. Something to check, anyway.
Years ago I tried several times to repair my wife's old Kitchen Aid mixer. I don't remember the particulars, but the governor was a mechanical weighted device and it could have been moving one of the brushes to regulate the speed. Are they still made that way? If so, the movable brush might have slipped so far as to cause a reversal of the motor. Does the speed control still change the speed?