Pitch Bend

Basic Bends – Kidtunes Electronic Keyboard

Sam

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.

Basic Bends – Little Tikes Pop Tunes Keyboard

Sam

The latest toy to come across my work bench was a Little Tykes Pop Tunes Keyboard. This toy stood out to me at the thrift store for a few reasons. First and most obvious is the awesome LED ring located between the power knob and speakers. Further it had some weight to it and appeared to be solidly constructed which gave me some hope for what may be found inside. Finally the song samples made it stand out from a lot of other toy keyboards I had played with. Rather than ear shattering renditions of “Old MacDonald” or “Mary Had a Little Lamb” the pop tunes keyboard featured recognizable (if a bit outdated) popular music  (“ABC” by the Jackson 5 for example).

Upon opening it up I found a fairly simple SMD circuit board with a black blob IC. There were quite a few transistors and resistors though a large quantity of them seemed to be associated with the LED functionality. Still there was plenty to play with so I set to it.

The first step (as with all my toys) was to set up a kill switch and line out for the toy. For the kill switch I simply cut the battery positive wire and placed a switch on it. As far as the line out I cut the speaker positive wire and ran it through a toggle on – on switch. The other side of the on – on switch I ran through a 1K resistor and into the tip of a 1/4 inch jack. I then placed a 10K ohm resistor between the tip and ground and ran a wire from the ground back to the ground point on the speaker. I recommend experimenting with different resistor values to get the volume level you require as it can vary from device to device and also depending on where you are sending the signal.

Next up I set up a pitch bend on my Pop Tunes Keyboard. First off a big thank you to alienmeatsack who made a great post about this toy on Electro-Music.com and led me to this bend. This pitch bend is slightly different than the ones I’ve used in the past as it makes use of three points on the board rather than replacing a single resistor. For this bend I used R1 as the pitch base and soldered it to the center pin of a potentiometer. I then connected the outer pins of the potenetiometer to R07 and R011 which shift the pitch up and down respectively. The toy will crash if you shift to far to either side so you may want to buffer the pot with resistors on the outside pins. I found around 4K to 5K worked fairly well for this but there is no substitute for experimentation.

I was blown away by the low end bass when the pitch was shifted down on this device. The quality of the rumbling drones you can produce are just incredible for a toy like this.

Alienmeatsack also talked about getting good results from a voltage starve on this device so I may try that out. And I’ve found a few glitchy areas on the board which I would like to investigate. I should be back to update you on my progress soon.

NOTE : Shortly after writing this post I was experimenting on this board trying to force a loop when one of the resistors cooked itself… There was a little puff of smoke and many tears. I will come back to this toy and see if I can replace the resistor and get it running again but it may be on it’s way to toy heaven. This problem was not caused by the pitch bend which seems to be very stable and produced excellent results but if you are exploring the board be careful as some of the resistors appear to have a very low tolerance.

Vtech Apple – Demo

Sam

Hey guy’s I just created and uploaded a quick video to show off my progress on the Vtech Alphabet Apple. Unfortunately I was having some issues with my portable amplifier so I ran it through the internal speakers but this should still give a good idea of what the bends I’ve completed so far can do. The demo starts off a bit slow but picks up after 1:20 or so. I also get into a really interesting glitch near the end of the video using the voltage starve.

If you want to have a look back at any of the previous posts they can be found here :

VTech Apple Part 1 – Kill Switch and Line Out

Vtech Apple Part 2 – Exploration and Pitch Adjustment

Vtech Apple Part 3 – Voltage Starve

Vtech Apple Part 4 – Body Contacts

Vtech Apple Part 5 – 555 Trigger Oscillator

 

 

Speak And Spell 2 – Pitch Bend and Hold

Sam

Pitch Bend and HoldAfter a lot of experimentation and some frustration I feel like I am beginning to wrap my head around the Speak and Spell’s operation. This is by far the most complex toy I’ve attempted to bend and as such there has been something of a learning curve as I explored the circuit and began manipulating it. That being said because this is such a popular toy for circuit bending I’ve been able to find a wealth of information to supplement my own experimentation and give me direction as I delve into this project. Today I’ll take you through the addition of a pitch bend up knob and a hold switch to my Speak and Spell.

Pitch Bend

Speak and Spell Pitch BendFor the pitch up bend I actually used three points, I initially found and started experimenting with the pitch bend using the two points on the board above (The 2nd and 4th pins from the right on the synthesizer chip) but found I was able to get a greater range by connecting the third lug on the potentiometer through a resistor to the point shown on the smaller board on the right side. I used a 100K pot and a 15K resistor though I recommend experimenting with different values until you find what works best for you.

Hold

wp-1467656667322.jpgHold and loop functions can be some of the most fun bends on any device as the allow you to create a constant repeating noise from the device which you can modify or play with in all kinds of ways and from my research into the speak and spell I understand it has a number of these type of bends available. Above is shown the first of these bends I was able to locate. If the switch is flipped while the device is making a noise it will continue to make that noise until it is flipped back down. You can then modify the noise output using the pitch bend.

VTech Apple Part 4 – Body Contacts

Sam

circuit bending vtech appleThe next stop on our circuit bending exploration of the Vtech Apple is going to be to add some body contacts. I really love body contacts as a control method as you can get a lot of range and really interesting tremolo effects with very little effort. The bend I’ll be adding them to is a second pitch modification I found while exploring the circuit. Oddly enough this bend seems to change between modifying the pitch up and down dependent on which mode the toy is set to (using the worm on the right side), On the modes where it lowers the pitch you can get extremely low droning noises using the body contacts which I’ve been really enjoying.

VTech Apple Part 1 – Kill Switch and Line Out

Vtech Apple Part 2 – Exploration and Pitch Adjustment

Vtech Apple Part 3 – Voltage Starve

Vtech Apple Part 5 – 555 Trigger Oscillator

Vtech Apple - Body Contacts CircuitThe above photo shows the two solder points on the board I used to produce these effects, Once I had attached the wires I experimented with a number of different control methods and components including potentiometers, resistors with switches and buttons, and even strings of capacitors and LEDs (too see what would happen). I was able to create a number of strange effects but the one I found most interesting and which worked most consistently was body contacts.

Once I’d settled on a control method I drilled holes in the case and threaded 2 screws through them. Though I used screws on this project there are really limitless materials you can use to create body contacts. Any conductive piece of metal should work so it is really a matter of taste. Some examples I have seen used include thumb tacks, guitar strings, conductive tape, pennies or nuts and bolts, the possibilities are endless.

Vtech Apple - Body ContactsOnce you have the screws threaded in place you simply solder the wires onto them. I try to strip a longer portion of the wire than normal and wrap it around the screw to ensure maximum strength and conductivity. To finish it off I typically apply a healthy glob of hot glue over each screw (liquid electrical tape also works if you have it) to hold them in place and to make sure nothing inside the case comes in contact with them.

Now you can close up the case and start playing with them. Try using different fingers to touch the contacts or different hands, tap on one contact as you hold the other or slide you hand back and forth across them. Take notice of the slew of interesting ways you can now control your device and above all have fun.

Vtech Apple Part 2 – Exploration and Pitch Adjustment

Sam

circuit bendingIn Vtech Apple Part 1 I got started bending my new Apple toy by adding a kill switch and audio output. Now with those modifications in place we can really start to have fun with the circuit, today I’ll be taking you through some cursory circuit exploration and I’ll add my first bend to the circuit, a basic pitch/clock control. Before we get to far in though I’d like to go over the 2 main techniques I use to explore a circuit for possible bends :

Lick and Stick

This is something of a “wide brush” approach as it is not exact but can help to identify areas where bends will be possible. Typically the first thing I do when I open up a circuit is trigger a noise, lick one of my fingers and begin lightly pressing on different solder connections across the board. When doing this your finger will act as a connection between the points it touches (with a small amount of resistance added) and you should be able to start eliciting different reactions from the circuit. As you go mark down on a photograph or a piece of paper where you were able to get different effects from.

Probes

Once you have found some possible bend points it is time to refine and identify exactly which points you’ll be attaching wires to. To do this it is best to use a set of connected probes. If you do not have probes on hand you can make an impromptu set very easily by connecting two jewelers screw drivers with a set of alligator clips. Touch the probes to the different solder points you identified with the “lick and stick” method, To explore further options you can try placing different resistors or a potentiometer between the probes with alligator clips. Again mark down any bend points you identify on a photograph of the circuit or a piece of scrap paper.

Pitch Bend

Vtech Apple - Pitch Bend CircuitTypically the first bend I complete on a toy once I’ve explored the circuit is a basic pitch bend. On most toys the clock speed for the processor is set by a resistor placed somewhere on the board, through my exploration of the circuit I was able to identify that this was done using the resistor marked R1 on the bottom of the circuit board (highlighted above) when I bridged this resistor with my probes or with another smaller resistor the audio sped up substantially and the pitch rose.

From here I removed this resistor using my de-soldering tool and attached two lengths of wire, one from each end of where the resistor had been. Once these two wires are in place you can begin experimenting with different potentiometer values to find the one which works best. I will often also experiment with a rudimentary voltage divider by attaching the third lug on the potentiometer to ground which often gives you a wider range of pitch though I did not have success with that method on this particular toy. I ended up getting the best results using a 1M linear potentiometer. With this toy I also found whenever the potentiometer was turned to too low of a resistance the toy crashed. I was able to solve this problem by adding a 47K ohm resistor along one of the wires leading to the potentiometer to stop the resistance from ever dropping below that point.

Apple - Pitch Bend WiringOnce you’ve soldered the potentiometer and resistor in place you need only to drill a hole, fasten the pot in place and secure the wires. Close up the toy and you’re done, you’ve now got a pitch bend knob to modify the pitch and speed of your devices audio output. During my exploration I was able to identify a few more possible bend points so next time we can start getting into those and perhaps find an interesting way to fill the extra hole I made on the left side of the above picture. Until next time, Have Fun!

Vtech Apple Part 3 – Voltage Starve