Sony WM-EX631 Speed Control
The MM1279XVBE is a motor controller IC used in the WM-EX631 stereo cassette player Walkman. An interesting feature of this driver IC is that it has a comparator between pins 9, 10, and 11, and the variable speed control is achieved through setting the bias at the non-inverting input.
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Sony WM-EX631Inside Look
Drive Belt
Speed Control
Cassette Compartment
Audio Tape Head
Battery Compartment