The Sunbeam Retro Mixmaster is a remake of the older Sunbeam mixers of the same series. Not as well built or quite as nice but they work and look all right. I picked one up free as it wasn't working and thought there can't be too much wrong with it. Here is how to open one up without destroying it.
There are no visible screws and that is often a bad sign. Not today! Push the Boost switch forward. Carefully lever the back end of the boost button up. It should un-clip and lift off.
Remove the small screw from the front end of the boost housing.
Lift the black top handle cover keeping it parallel to the mixer. This will avoid destroying the locating pins further back.
Pull the top of the chrome front cover out until the tab with the hole just clears the main body.
Pull the front cover upwards to release it from the main body. It will lift off a tab and come free.
Using your favourite technique, (mine being destroying the tip of one of my favourite flatheads,) remove the two triangular tip screws from the front end of the main body. Hey Presto, you now have access to the guts of the appliance.
This is as far as you need go if you know what to do from here. Feel free to continue to see how mine was diagnosed.
Step 7: Diagnosis.
When I tried to turn on my mixer, nothing happened. After looking at the circuit board I thought it was probably the pot/switch that had failed. I un-soldered the pot/switch (after I removed the transistor to get access) and disassembled the switch half. Pretty simple switch, you turn the knob, the shaft turns and allows power to flow between the contacts. When I turned the shaft, the switch didn't move, suggesting a broken shaft.
I disassembled the pot side, finding that yes indeed the shaft had broken. This made it a theoretically easy fix. Replace the pot/switch and we are good to go. After a not-very-quick Google I decided that the very specific pot/switch combination required was too much trouble and junked the whole unit. If you really wanted to make it work and you had the same problem you could bypass the switch half by jumping straight across the pin points and just use the power-point to switch it on and off. The pot would be a lot less trouble to hunt down and replace.