Category Archives: Schematics

Schematics for various circuits.

Circuit Bent Doomsday Device Board Scan


Here is another board “scan”, this time of the Doomsday Device, a vintage sound circuit that lends itself to some good touch point circuit bending. The initial kit instructions only include 7 points of interest, but many builders of this kit have sent me modifications and their newly discovered bends. In order to document those hacks better we now have a blank circuit template.


To illustrate the point here is a close up photo from Jon on adding a 1 Meg potentiometer to control the overall pitch of the Doomsday Device.


Feel free to share your modifications in the comments. Enjoy!

Inside The Leap Frog Alphabet Pal

Beaked Fuckapede 2.0

by Austin

For better or for worse, it seems that many people’s favorite toy that I have circuit bent is the Leap Frog Alphabet Pal, aka the Fuckapede.  It is the the only toy that I have bent that has seemed to spark enough interest in other people for them to decide to write about it and it is almost always the favorite of people newly introduced to circuit bending.  This toy, despite being one of my less musical bent devices, seems to strike a chord with people. I think the cute and unique design of the toy itself, the demented make-over I gave it, and its simple bend interface, not to mention its penchant for generating curses, appeal to the lay-person and benders alike.

Here’s the original Fuckapede in action:


To hear the swearing, go to 1:48

Leap Frog Alphabet Pal, Unmolested

This foul-mouthed toy created quite a stir when it was first released by Leap Frog in 1999. Though the toys were never officially recalled, as I understand, many angry parents returned these toys. When I first found a working Alphabet Pal in a thrift store, I was immediately drawn to its unique design; I had never seen a toy put together in segments like the ‘Pal and the individual feet buttons intrigued me.  It’s also disgustingly cute. I noticed the toy had three modes, Letter Names, Letter Sounds, and Colors. I began playing immediately in the Letter Sounds mode, as I thought those would probably be the toy’s most interesting sounds. Pressing A makes a short “A” sound, as in cat, B makes “Buh,” C “Kuh,” D “Duh,” E “Eh,” and F “Fuh,” etc. I then, like countless children across America, pressed F and C in succession to make it say “Fuh-K.” To my surprise, it actually said what sounded pretty close to “Fuck.” I knew then and there that I had to bend this toy. Little did I know, however, that this would be one of the more frustrating bending projects I would face nor that this toy had apparently infuriated enough uptight parents to be re-engineered several times since its initial release.

While researching the ‘Pal’s F-word fiasco, I noticed that there seems to be some confusion about this toy’s swearing. A lot of people’s online comments seem to indicate that they think the toy has some sort of filthy Easter egg phrase that some crafty toy designer programmed so that it says “Fuck” when you hold down some odd combination of keys. Others think that later versions of the toy says “Fuck You” when “F” then “J” are pressed.  There seems to be a lot of uncertain response videos on Youtube. The actual case is simply that a surprising amount of cuss words can be formed with the toy’s Letter Sounds function, provided you have the uncensored version of the toy; I sat down with my cousins one day and we figured out as many different dirty words as we could make it say. It has quite the naughty vocabulary, from expletives as simple as “Ass” to the more complex “Cocksucker,” if your fingers are nimble enough and expectations for clarity low enough (see video). Leap Frog corrected later versions of this toy by programming it to insert another phrase already programmed into the toy between any of the objectionable letter combinations… pressing F then K on these censored versions sounds like: “Fuh” – “Hyuh, hyuh, hyuh, hyuh… That Tickles!” – “K”

Just a side note, I feel like parents should be more annoyed with later verions of these toys, having to hear “Hyuh, hyuh, hyuh, hyuh… That tickles” over and over, every time their baby happens to hit “F” then “K” or “D”-“I”-“K”or whatever.

Here’s a short companion video to this article:


These toys are a real pain to bend for several reasons. There is a thin, easily-damaged plastic membrane that contains the leads for the buttons in the three rear segments of the caterpillar’s body; kink the membrane and you’ll lose more than half the toy’s sounds.  To gain access to the toy’s brains in the front segment, you’ll have to peel up cardboard and hot glue from the bottom of the circuit board. The plastic feet buttons easily fall out, there is not a lot of real-estate for adding controls, and if the toy’s speaker is disconnected, it messes up the sound. To top it off, there are a number of different (and less bendable) versions of circuitry within seemingly identical versions of these toys. But I know you people out there, you’re like me; you really want to hear this toy say “Fuck” in a James Earl Jones voice and you’re not going to stop until you do. Let’s get started.

The Original Fuckapede, circa 2006

There are several versions of this toy, so it’s critical to select the correct version to bend. The toy we are after will have a green, truly segmented body; the bodies of later models of the toy are made to look segmented but are actually one solid piece of plastic. The revised version of the toy is censored, as are some versions of the ‘Pals with segmented bodies.

This is easier to see than it is to explain, the pictures below show the original and revised versions of the toy.  The first toy pictured below has the body design we want.  There are really glossy plastic versions with this body design that are censored or partially censored.  You want one that is less glossy than the one pictured, at least I think, but really, there’s no way to be absolutely sure if you have the circuit that I’m writing about without listening to and opening up the toy (and probably several):


These are later versions, they are censored, and I assume they are types we don’t want:

alphabet_pal_dont_want.JPG So, if you have a segmented ‘Pal, put batteries in the toy and hit “F” then “K.” If it says “Fuh-K” without saying “Hyuh hyuh hyuh hyuh… That TICKLES” between “Fuh” and “K,” that’s a good sign. The third potential indicator that you have the desired version of the toy is the Item Number. The Item Number is located on the bottom of the rear segment of the toy. The Item Number on the version we want for our nefarious purposes looks stamped or melted into the plastic.  Other versions have the Item Number Printed in black.  So far, I have only found the uncensored, surface mount circuit board in the ‘Pals with the stamped Item Number, though I have found other circuit boards in these as well.  If it’s green and segmented, open it up and compare it to the image below.  The circuit on the right is the one this article covers.

Bendable and Not-So-Bendable Alphabet Pal Circuit Boards

If your toy is uncensored but has regular-sized resistors on the board and its circuit board looks like the one on the left in the image above, you may not find any bend points (I didn’t find any good ones).  But I encourage you to try any way, if you have this version of the toy, and let us know if your results differ.

Now you’ve finally found the version of the ‘Pal that you want to bend (probably after buying and opening several) and you’re raring to go. Don’t get rid of those other caterpillars, they come in handy for spare parts. All I have done to the toy is add a simple pitch bend, but it still makes for good sounds. The Letter Sounds for T, C, K, X, P, and S are nicely percussive. H, M, R and U sound like weird grunts, groans, and sighs. For reasons I can’t remember, the first version I made uses several buttons and switches to connect different (and since forgotten) resistor values in parallel to a 500k potentiometer to create stepped pitch ranges which could be momentarily engaged or locked on (diagram 1).  The lettered resistors in the diagram refers to resistors in my added circuitry, the numbered resistors refer to the resistors on the ‘Pal’s circuit board.  Look at the ‘Pal’s circuit board so that the component labels read right; the solder points in the diagrams are determined by this orientation. I did no de-soldering on this project.

Diagram 1:

Diagram 1

I decided to simplify the bends by substituting body contacts for the buttons and switches for the new ‘Pal I cracked open and bent for this article. I find that body contacts are usually quite expressive as a general rule, but I think the reason I may have abstained from adding them to the first Fuckapede is that they are a tad touchy on the second Fuckapede. They seemed rather stable when I was first putting the second one together, but when I plugged it into my amplifier they caused the toy to crash like crazy. I couldn’t figure out what was causing this problem, so I tried a number of different audio output configurations to see if it would correct the problem. What finally corrected the problem was not changing my wiring but rather plugging my amplifier into a properly grounded outlet. Don’t ask me why this worked, I’m sure I’m breaking one of the cardinal rules of circuit bending by even plugging it into a non-battery powered amplifier, but it seemed to mostly correct the problem (though the body contacts do still seem to cause it to crash/reset from time to time, especially when the potentiometer is turned far to the right or left).

Leap Frog Alphabet Pal Bend Points

Leap Frog Alphabet Pal Loose Controls

Leap Frog Alphabet Pal Bend Lead Placement

Before I wrap up, I’ll add a few helpful hints about bending and decorating this toy. The first thing I did after opening up the front compartment, under the Alphabet Pal’s head, was disconnect the rear button membrane from the main circuit board; I found out the hard way that if you compromise this membrane, the rear buttons won’t work and you’ll have to find a replacement membrane from another Alphabet Pal.  Avoid this by detaching the rear three segments immediately from the front segment and setting them aside to reattach later.

I mounted the output jack in the first Fuckapede’s forehead, but it was a very difficult installation, as you have to entirely disassemble the head. Even though the jack looks really cool there, I had to heat and bend the light-up antenna assembly inside the head to accommodate the jack, and the cord still doesn’t quite insert all the way. If you absolutely must put the jack in the head, you might try mounting it in the side of the head or using an 1/8” or RCA jack instead of a ¼” jack.

Ubiquitous String, Out, 1/4? Audio Output Dongle, In

Another option would be to do what I did in the second version of the Fuckapede, which is to make a dongle for the audio jack. The Alphabet Pal has a string that protrudes from its chest which, when pulled, plays the alphabet song. The string is attached to a button assembly that presses a button on the main circuit board. The string’s handle is almost always broken or missing when you find a ‘Pal. I removed the string and wired the button leads to a normal push-button switch, now mounted to the left of the string hole. I made the dongle similarly to how I make the jacks for my Crème DeMentia Bottle-Cap Contact Microphones and simply ran the jack’s wire through the hole left by the removed pull-string. I coated the jack assembly and some of the cord with hot-glue and Plasti-Dip to give it the look of an organ popping out of the caterpillar’s chest. The eyes were painted using acrylic paint covered with clear nail polish.  The original Fuckapede’s fangs are plastic fork tines.  The new Fuckapede’s beak was stolen from a chicken toy and its tongue made from a rubber band, two zip ties, red Plasti-Dip and hot glue.

The green plastic seems to be very prone to collecting paint scuffs;  they can be removed handily with a Mr. Clean Magic Eraser. There is space to mount controls in the rear segments, but make sure that you run your wires through the hole in the red connecting donuts before soldering them in place. I added a green lanyard to the rear of the original Fuckapede so you could hang it around your neck when playing it, but it’s still pretty awkward to play.  This toy automatically shuts off (and plays an annoying song before doing so) and the time before this happens gets shortened or extended if you have the pitch dial turned up or down, respectively.

Thanks for reading!

Creme Dementia’s Recipe for Circuit Bending the Protech Drum Toy RY-1286T, pt. 1


Greetings LoFiers! Tommy from Roth Mobot supplied me with a dupe of a toy I’ve bent before, the RY-1286T Protech Drum Toy. Tommy has the best toys.

I’m very fond of the Protech Drum Toy (or the “RY-1286T” if you read it’s most likely peeling label on the back), and it has special significance for me, as it was the first toy that I ever circuit-bent. With instruction from Patrick from Roth Mobot at a free workshop in 2005, I was able to find and figure out how to wire a pitch bend and a noise/buzz bend. Thus was born the Drum Invader, and it remains one of my favorite projects to this day, here it is in action:

The toy pretty much looks like this when it’s not bent, minus anything silver on the outside you see in the video. There are no star stickers, either

Here’s a picture of the circuit board of the Protech Drum Toy that I bent. It’s followed by a schematic drawing of my bends, and an explanation of these bends.

Circuit Bending Protech Drum Toy

The Bends Explained:

A nice pitch sweep can be attained by soldering a 1M potentiometer in the configuration shown, using leads from the right sides of resistors R3 (center lug), R1, and R5. Nicely responsive body contacts can be installed using those same points. What really makes this toy sing, though, is the noise/buzz bend. By connecting the top (-) leg of C3 to J7 on the board, you get a loud buzz. By varying the components between these two points, you can control the timbre and volume of the buzz. I used a 15k resistor and a 473 capacitor to get two different buzzes. Try some other components! These buzzes are, for some reason, affected by the pitch bends. This essentially gives you two different wave forms that are pitch-controlled by the potentiometer and body contacts. The most interesting tones result from masking the the drum tones with these noise bends; the rhythms created by the toy “modulate” (not sure if this is the correct term, but you get the idea) the buzzes, creating rhythmic buzz “melodies” out of the drum beats.

Circuit Bending Protech Drum Toy

So, you may ask, why am I re-opening this toy now? For starters, some joints were poorly soldered and it’s beaten up from touring. Also, despite its excellent bending potential, this isn’t the most well-designed toy on its own; the small buttons that allow you to record patterns for playback and select rhythms and drum pages have a tendency to stick down and the on/off switch has a tendency to get really staticy. I think it’s ripe for a re-house and I think I may do the both of them simultaneously, creating one Amalgam of the two toys. So, why not document my progress for all you happy people?

We’ll call that Part 2.

Creme Dementia’s Recipe for Bending the Sesame Street All Star Band by Golden

Greetings all you people out there in Internet Land! This is Austin, aka Creme Dementia, and this is the first of hopefully many posts that I will be making for I’ve been circuit bending for about 3 years now and this is probably completed project #12 or so. I was introduced to bending by Patrick of Roth Mobot, while living in Chicago, and through him I have met many other benders. Daniel, aka Spunky Toofers, inspired me to start tackling obscure toys, ones that I haven’t seen bent much or that are just pretty whacked-out to begin with. The Sesame Street Keyboard is a good example of a pretty “whacked-out to begin with” toy, and the bends that I have found make for a lot of fun with the toy. I have come across 2 of these toys in my thrifty adventures; with the help of a third from eBay, I was able to Frankenstein-together the finished result you see. If you take the precautions I list in step 1 and solder quickly, I think you will probably only require 1 of these toys to bend it as I have.

I wrote this in a step-by-step manner in an attempt to make it accessible to beginners and pros alike. If it’s TMI, so be it, it’s better then TLI. My custom paint-job was done by splashing red nail-polish across the surface and adding several coats of clear-coat (I masked off the “On” button and keys with masking tape and newspaper). I did the eyes on the Sesame Street Characters in a similar manner with white nail-polish, markers and clear-coat. To mount the PCB buttons, I made a paper template and marked and drilled the holes for each leg for each button. I then soldered two leads to each, fed the leads and the legs into the holes, and put a dab of JB Quik Weld epoxy putty under each button to hold it on securely. Otherwise, this is all pretty simple, save for de-soldering. I’m sure you could creatively skirt having to desolder anything in this project, but I found it made things easier for me. I enjoy desoldering and its a good skill to learn if you haven’t yet. Treat yourself to a desoldering pump, it’s a great gadget to have around.

Alright, so here we go:

The Sesame Street All Star Band Unmolested:


Bending The SSASB

1) Before you open the toy, here is a list of some key precautions and some notes on my bends; read these instructions thoroughly before you get started. There are two shorter screws in the outer case, those go in below the numbered rainbow keys. A good way to hold onto your screws, as taught to me by Patrick of Roth Mobot, is to stick them to the toy’s internal speaker, but I’d get a container for them if you plan to have the toy open for any more than a day.

There are several ribbon wires and plastic membranes with printed traces inside the toy, be very careful not to bend or break these, as they could easily disable the buttons. I went through 3 of these toys before coming out with the finished product, and I think one the problem I encountered may have been from unknowingly breaking one of the wires in the ribbon wire. I encountered a membrane breakage in another toy, the Alphabet Pal (Fuckapede… see my MySpace page. Also, I do not give specific capacitor values for the last bend in these instructions; the values you could choose are rather open-ended. You’ll want to either experiment with a capacitor substitution box to find the values you want or experiment with capacitors that you have on hand. All the values I used were below .22 uF. Also, there is an auxiliary battery compartment with button cell batteries under the main circuit board. I removed these batteries and the leads traveling to it; I assume they were put there to power the toy at the point of purchase. When you load in AA batteries, the batteries push open a switch that breaks the connection to these auxiliary batteries, which are left to rot inside the toy. Most likely they are dead, as this toy is from the early 90s. Test them for charge and dispose of them properly if they are dead. Don’t just throw out those batteries, collect them and give them to the Lion’s Club or Radio Shack or Walgreens or the Fire Department or SOMEONE for proper disposal.


The SSASB Circuitry Bend Points

2) Looping –

Solder leads to pins 13 and 14 on the Sesame Street All Star Band 9124 Chip. Connecting these points will give you looping sounds. I wired a toggle and push button switch in parallel which would connect these two leads through a 47 ohm resistor, so that you can audition and hold loops.

I used solid core CAT5 strands to solder to the chip; they solder quickly. Quick soldering is key to avoid overheating and damaging the chip, which may also have been the culprit behind the problems I encountered in my first attempts at bending the toy.


My Control layout inside the SSASB Handle – It’s about the most open space you can find inside the toy.

3) Body Contact and Pitch Switch –

Desolder R6 from the SSASB Keyboard circuit board and retain it. Solder a wire lead to the remaining hole where R6 connected directly to C3. Connect a second lead to the loose end of this lead. Mount an on-off-on switch (SW1) in the case and solder the joint of these two leads to the middle terminal. Mount a body contact in the case and solder the remaining lead to it.

4) Pitch Switch Continued –

Attach the desoldered R6 to one of the outer terminals of SW1, and solder 2 wire leads to the other end of R6. One of these leads will connect back to the SSASB keyboard, soldered into the other remaining hole where R6 had been removed. The loose lead will connect in the next step.

SSASB Pitch Dials – I put these on the left side of the keyboard

5) Pitch Dials –

Mount three potentiometers in the case, two (or more) 1M potentiometers and one 5K potentiometer. Wire them in series, and add a 180 ohm resistor at the end of your loose lead and solder the other end at one end of the sequence of three potentiometers. At the other end of the potentiometers, solder a wire leading to the remaining terminal of SW1.

6) Capacitor Bay –

C3 on the SSASB Keyboard also affects the pitch when you connect other capacitor values in parallel with it; they drop the pitch into a different range. I added 4 PCB momentary buttons that put 4 different capacitors in parallel with C3. I would recommend experimenting with different capacitance values to get the sounds that you want.

7) Cut the positive lead from the AA battery compartment and add a reset switch (the looping can get crashy). Add an output and possibly a speaker switch and you are all done:



SW1 will give you three modes, Normal, Pitch Controlled, and Open. Normal mode is when you route it through the pole that R6 is soldered to. Flip it that way and turn the toy on. Press a sound, and during that sound, move it to “Open” (off). This will give you a long stream of noise that will last for quite some time. Move it to the last position, Pitch Controlled. Turn the 1M potentiometers so that they are at 0 ohms, move the 5K potentiometer to center and it should sound about normal. The 5K potentiometer will give you pitch control over the sounds above and below its normal pitch range, while retaining the integrity of the original sounds. As you add more resistance with the 1M potentiometers, it will get that shimmery quality of the noise stream caused by breaking the pitch circuit in “Open” position. While the toy is making a noise, hold down the looping button. If the sound starts looping, you can lock it on with the looping switch. Play with the controls in tandem, there’s quite a vast sonic range.

PLEASE, use this is as a jumping-off point and experiment, you might find a preferred layout or different control options.

The draw to me for this toy was its strange appearance and all its great factory tones, its easy dis-assembly and the fact that it’s made by Golden. More on that later. Thanks for reading, I will hopefully have some video of my bent toy for you to enjoy soon.

Da Da Da da-da DAH *SMASH* Oh Boy!


Yamaha RX-17 Circuit Bending

Yamaha RX-17 Circuit Bending Schematic by Eraser -
Eraser from was kind enough to share his bend point schematic for the Yamaha RX-17 drum machine. The points are labeled with pin number and a chip ID along with their suggested corresponding connections. More info at RX-17. Pictured below is another RX-17, recently crafted by Logan aka LameBoy from 8Bit Collective.

RX-17 by LameBoy

RX-17 Modding by LameBoy
The controls and RCA patches are on the main PCM chip without any extra circuitry like timers or sequencers, nice wooden case, and a kick ass modular look.

Casio SK-1 Modifications from back when

Casio Twins sk-1 modified
Here is a link
that Roger sent me a while ago. Its a website by Frans Samshuijzen with detailed descriptions of some mods that he did to a set of Casio SK-1 keyboards appropriately titled: “Casio Twins“. The mods include a full pitch mod with the use of a TI 74LS624 voltage controlled oscillator. It is also worth noting that a 555 timer circuit would theoretically do the same thing, except that the max frequency of a 555 is about 2Mhz and with the LS624 chip the schematics indicate a range of between 1.5 and 10Mhz with a max of 20Mhz. The downside however is the fact that the LS624 is far more expensive, $2.55 a pop. Still worth every penny considering that the Casio will provide for a full 3 Octave mind melting sound experience, along with longer and grainier recording times. Other mods include a nice line level adapter schematic for the microphone input and a remote trigger option. Audio of the improvisations on the Casio Twin set can be heard here and there is more information about what all the controls are here.



Building Guitar Effects + Other Circuits

Random Note Generator
This link I’ve been hanging onto for over a year now, Laurier’s Handy Dandy Little Circuits. The guy has quite a collection of various Wah-Wah circuits ranging in complexity and features like an added Fuzz circuit. Through some browsing other little circuitry gems can be found including this simple oscillator collection and a random note generator. Good pleace to get some ideas for experimenting.

Casio Sk-1 with a Video Out

Casio SK-1 Video Out

Gijs of has just sent me some information on their recent experiments with patching signals from an Casio SK-1’s ROM chip to a video monitor. The circuit is simply a diode to prevent the back flow of current and a resistor to drop the +5 Volt logic gate to a +2 Volt required for generating a video signal. The color of the pixel is determined by the voltage in between 0 ( Black ) and 2 ( White ), so if multiple points on the ROM chip were mixed with various resistor values color images will occur. Gijs’ result is a series of lines that appear on a monitor in a scrolling fashion. The resulting image is neat and in sync with the sounds generated, however it is out of sync with the screen. The NTSC and PAL video standards require a sync pulse to be sent every so often, without it the image will scroll. Very nice work and I am sure that this technique will work with other circuit bent devices.
Video on of the bend is on YouTube.

Casio SK-1 Video Out Circuit Bent