Bending the Coleco Talking Teacher
Here's my take on bending the Coleco Talking Teacher toy. There are a few schematics floating around, but the bends on them don't quite work as advertised.
The two of the glitch loops use 25K potentiometers in such a way that the bend is deactivated when the potentiometer is rotated to maximum resistance. This means a switch is not necessary to activate the bend and that the bend is adjustable. Different sounds are produced by these bends a different resistances. At lower resistances the sound will subtly glitch between what it should be and a slightly off variation. At higher resistances, the sound is fully glitched and unrecognizable. The bend which does use a switch did not react to variable resistance in an interesting way.
To perform the pitch modification the onboard pitch adjustment trimpot must be removed. Because this part of the board is crowded, the easiest way to do so by wiggling the trimpot until it breaks free of the board. After this has been removed, a new 500K potentiometer can be soldered in it's place.
This is one of the most stable talking toys I have bent. The long and short loops are repeatable, so the glitches can be played like you would a drum machine or keyboard. The sound is also very clear.
Here is a schematic for the best four bends I could find: