I’ve been working on a new toy and I wanted to give a quick update on my progress with it. Today I’ve been working on a Kidtunes Electronic Keyboard which I picked up at Value Village. The Kidtunes electric keyboard is made by a Chinese company called Scientific Toys and though I wasn’t able to find an exact year I would assume based on the circuit that it came out in the early 2000s. The keyboard itself is a little odd as it has two octaves (from G to F) but is missing the second F sharp. I guess they assumed kids wouldn’t notice. The toy is monophonic (only one note can be played at a time) but has two distinct voices. There is a sustained organ voice as well as a shorter cleaner piano sound. The Kidtunes keyboard also features a demo mode and a low-high volume control.
One thing struck me as odd on the circuit board of this toy. It looks like, though they have used a black blob IC, they manufactured it separately and then added it onto the board. This has left easy access to the pins of the IC where it was connected to the main board. Though the majority of these solder points are triggers for the keys it still allows a level of access which is rare with modern toys. Additionally all of the components outside the main IC are though hole which allows for fairly easy bending and modification.
The first thing I added to this keyboard was a simple pitch bend. To do this I located the pitch resistor and removed it. On this toy the pitch resistor was located immediately below the IC. The resistor I removed was 220K ohm so I replaced it with a 100K ohm pot and a 150K ohm resistor in series. While playing with the pitch bend I also noticed I could illicit some very interesting glitches by attaching one of the legs of the pitch resistor through a capacitor to the base of a transistor on the far left of the board. I wired this up through a switch and moved on to see what else was available.
The next two bends I found were fairly straight forward point to point connections which I wired through switches. The first (red wires) involved connecting one of the resistors on the board to the trace running across the emitter of the transistor I mentioned in the pitch bend. This bend seems to impact the sustain of the Kidtunes keyboard. By connecting these points all sustain is removed so that the keyboard sounds like an xylophone. The second (yellow wires) connects one of the trigger points to a resistor on the board. When the keyboard is in organ mode this has the effect of holding any note played indefinitely when the switch is turned. Further in demo mode this will cause a note to play repeatedly. This second functionality will be extremely helpful while searching for further bends as I will no longer have to keep pressing keys.
That’s as far as I’ve gotten with this one so far. If I am able to find more I will be sure to provide an update. Also I should have a video of this toy online within the next day or so.