I would like to understand in detail what this circuit of an old kitchen mixer consists of.




On the left, just before the motor phases, there is a diode bridge and an RC filter, but I'm interested in figuring out what signal is input to the diode bridge, directly the AC input?

1. there are two red buttons, I can't tell if they are just buttons or there is something else inside, I usually see the tiny 4-pin buttons for use in breadboards, not as big as these in the picture.
2. the blue component has 3 pins and a small dissipator plate on top (can't be seen in the picture), what is it used for? Is it a transistor or a linear regulator?
3. the green resistor?
4. the purple one is an inductor? (it's MKP62 275 - X2 684K 40/110/56/B)

The diode bridge converts AC input to DC, so I exclude that the components just listed are part of a DC/DC converter.

 

It states DC motor so hence the bridge! but is there any markings on the blue Mosfet/Transistor?

 

The blue diode by the small gear is a Diac, so the three legged device must be a Triac operating in phase control to regulate the motor’s speed.

 

It states DC motor so hence the bridge! but is there any markings on the blue Mosfet/Transistor?

The blue diode by the small gear is a Diac, so the three legged device must be a Triac operating in phase control to regulate the motor’s speed.

Unfortunately there is nothing written on it, in the pcb it is indicated with Q1

 

The blue diode by the small gear is a Diac, so the three legged device must be a Triac operating in phase control to regulate the motor’s speed.

So if I understand correctly, Triarc adjusts the phase angle of the AC voltage so the amount of power delivered to the motor is controlled. When the phase angle is adjusted, the effective voltage applied to the motor changes

Am I wrong?

 

You have understood correctly.