Basic Bends – Little Tikes Pop Tunes Keyboard

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renditions of “Old MacDonald” or “Mary Had a Little Lamb” the pop tunes keyboard featured recognizable (if a bit outdated) popular music  (“ABC” by the Jackson 5 for example).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.

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Toy Keyboard Salvage

Scrap Keyboards
So I’ve been tinkering away in my workshop on a very cool new project I think you’ll enjoy, it is still a work in progress but I should have it finished up and online next week for you guys to check out. In the meantime though I wanted to share some keyboard salvage pictures I took while tearing apart some toy keyboards I had kicking around my shop.

As someone who compulsively buys cheap used electronics from thrift stores every so often I find the random chunks of plastic lying around my shop are starting to pile up and get in my way. When this happens my destructive tendencies get a chance to come out and play. I can spend some time reducing these large monstrosities to their small and easy to store component parts.

Further I know if you’re anything like me you want to see what’s inside every toy you encounter. I’m very much of the mind that the more photos of toys and devices opened up with their innards exposed there are out in the world the easier it will be for us as circuit benders to judge toys at thrift stores or garage sales without the weird looks you get when you start taking things apart in public. Today I have three keyboards I’m going to pull apart and let you have a look at.
Simba Super Concert

The first is a “Simba Super Concert Keyboard”  which works relatively well but I have had very little luck bending. The buttons on the face seem to have been poorly constructed and many are not working very well. When I trigger these buttons directly from the board the sounds are still there so it seems this is just a mechanical issue with the keys. This is reassuring as there are a number of interesting sound samples on the board (animal sounds and different instruments) which I may incorporate into a future build.

From the board you can see there is very little going on, the small vertical board holds a black blob IC and a pitch resistor but little else. The reverse of this board simply contains a large button matrix.

Chinese Keyboard
Next up is a cheap toy keyboard from China I picked up at a discount store. There is no brand printed on it but it appears to be made by Jinjiang Shengel Toys ltd. I have to admit I did not have high hopes for this one, it sounded foul and felt worse. The plastic was extremely lightweight and poorly constructed. My favorite feature was the USB port on the right side of this photo, which is to say the rectangular hole in the body labelled USB with no port or supporting electronics to be found.

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I did have one pleasant surprise when I opened this keyboard up though. It’s probably a bit hard to make from this photo but this is a fully functioning LM386 amplifier which was used in the keyboard. I was  pleased to find an LM386 as it is a chip I am fairly familiar with and one I have worked with in the past. With some simple modifications I should be able to add gain and a volume control to this amplifier and re-use it in a future project.

20170116_175907_HDR
Last up for this keyboard salvage session was a Kawasaki Pro-37 keyboard. Unfortunately this keyboard was in pretty rough shape. It was given to me used and the sound circuit had been essentially destroyed from battery corrosion. I didn’t get a picture of the inside for this reason but it was not a pretty sight. That being said I was still able to salvage some useful hardware from the toy.

Spoils
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So at the end of the day I walked away from these three keyboards with several large button matrices, Some small sound generating circuits, an LM386 amplifier, a few speakers (of varying quality), several battery compartments (cut out from the keyboard bodies), several sets of keys, a small pile of switches and buttons and most importantly some space on my shelf. Hope you guys enjoyed these keyboard salvage pictures. I should be back next week with an exciting new build.

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