Diagnosis
Motor is overheating due to excessive load or failed bearing. These are low-torque motors not made for prolonged runs.
How to Fix It
Unplug it immediately. Let it cool completely. The smell may linger. For next use: ensure you are not overfilling the cup. Liquid must cover the blades before starting. Use the pulse function; do not hold the button for more than 5-7 seconds at a time. Let it rest for a minute between pulses.
If That Didn't Work
If it still overheats with correct use, the motor windings are shorted or the bearing is seized. This is not user-serviceable. The base unit is a sealed assembly. Replace the base.
Heads Up
The burning smell is insulation on the motor wires. A continued short can be a fire risk. Do not keep using a base that smells hot on normal loads.