Ambiano Milk Frother (Aldi) Transistor motor replacement

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Error pattern: As soon as the milk frother is supplied with voltage, the motor starts to rotate slowly. Because of this, the power of the motor is insufficient to froth the milk. The problem was transistor Q3, which is used by the microcontroller to control the motor.

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You can now start the troubleshooting. To do this, supply the DC part of the circuit externally, e.g. by soldering cable ends to D8 (in the picture on the left side of the diode) and to ground (in the picture at the very bottom left of the board) and a laboratory power supply. I have always used 20V.