I've had this motor at least for 5 years (salvaged from something) and I remember it working then. However it doesn't work now (5 VDC mobile charger) and so I opened it up expecting to see just the split rings. But I was surprised to find this circuit built in it. Why does it need that circuit and what does it do?
The motor body says – (If the picture is not clear)
6JS E 06 R
2400N 6V
Link to a better quality picture
http://postimg.org/image/l4unckkin/
Best Answer
That looks like a DC motor of the type used in tape cassette players.
For music reproduction with accurate pitch constant motor speed is required. Achieving this in battery powered equipment requires addition of a voltage regulator or speed controller as DC motors' speed varies (nearly linearly) with voltage. The potentiometer in the motor allows the speed to be factory set.
I modified one such motor on a good tape deck, adding an external pot and switch to allow some pitch adjustment so that I didn't have to keep retuning my guitar between tracks / albums.
The TDA1151 seems to be one simple device intended for such applications.