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[phantompowers]

This is a great keyboard to bend as it has a resistor controlling the pitch and a record playback feature. The sounds aren't too bad either. If you can't get a second-hand one, (I paid £2 for mine), they sell them at Argos for £9.99 or two for £15. I'm also using a 555 timer module to control the pitch and the playback feature.
Check out my video and then I'll explain how I did it.

Circuit Bent Chad Valley Keyboard With Pyramidi Controller..AVI

There are only 3 points to solder to on the main circuit board and they are easily accessible.



The voltage starve mod was achieved by cutting the red lead coming off the battery pack and putting a 1K pot in series. This will reduce the input voltage which really messes the sound up! This bend is worth trying on most keyboards and toys but sometimes reducing the voltage disappointingly only lowers the volume.

555 timer circuits are a circuit benders secret weapon as they can be used to create loops, vibrato and tremolo effects and as a trigger for bends as well as many other uses.
The circuit is really easy to build as the 555 timer chip has only 8 legs, one of which you won't use and only a few components.  I made my circuit out of cardboard and poked holes in it with a dart for the components to fit in and then jumper wired it all together.
Alternately you can buy these ready made or in kit form from get lo-fi.com.



Original schematic on 555 timer LFO came from - http://www.mikmo.dk/cblfo.html

Since doing this video I have fitted a timer circuit inside the keyboard to control the vibrato. I also added a capacitor across the legs of the LED inside the vactrol which can be switched on and off. This gives a ramp wave effect and sounds amazing.
Details on vactrol and LFO arrangements can be found here - http://www.getlofi.com/?p=1978

I think that covers everything. If you want more info let me know.

Happy bending!

[phantompowers]

These keyboards are also marketed under the brandname, 'Beanstalk'. Get one!!

[Circuitbenders]

Nice job.

Is this your site? http://www.mikmo.dk/cblfo.html

I'm not sure if your board layout is actually originally from that site or they got it from somewhere else, but i thought it'd be polite to put up a credit link 

[Bogus Noise]

Hahaha, that's mad, I just did pretty much exactly the same mods on one here last week! Minus a few LEDs, but with a different control layout and a distortion I got by bridging R7 on the amp/power board with a 47k pot.

Didn't have the 555 triggering the Playback button but might have to put that in... have used that technique before on a VTech Smart Start Scholar and an Endangered Species thing with great results. I'm torn between using a switch or replacing the osc circuit with a 556 for independant LFO control.

I found the voltage drop to work best when the keyboard's been pitched up quite a bit. Some cool glitchy clangs were definitely heard though

[phantompowers]

Sorry about the credit omission, I have modified my post. It was an honest mistake as I like to give credit when credit is due.

[phantompowers]

Nice one Bogus! I need to get another one of those keyboards,. Great sounds and really simple to bend.
I was playing around with it last night and the new mod I added, the ramp wave vibrato sounds amazing. On a slow setting it turns the mandolin into a ray gun!!
I didn't do the pitch up bend as I found it to unstable. Also the distortion bend I found was just like a heavy drone so I left it out. I would like to hear yours though.
I will be putting another vid up with the fitted 555 timer unit as soon as I get around to it.

[Bogus Noise]

Am going through a bunch of projects putting finishing touches and making videos, will post footage of this one up when it's ready

[boneless]

Thanks for the thread - I should manage to get photos of mine up sometime soon. Much fun.

One thing I have noticed is a recent degradation in the sound quality of mine - whenever a key is pressed I get clicky noise mixed in with the sound.

I'm not sure is this is because I'd been experimenting with crashes a lot - and how long I can keep it hanging on before it crashed -

- or because I'd been experimenting with a 555 timer and 4016 chip running off 9v to switch different bends off and on. I'm not to familiar with the 4016 and wondered if the 9v might have screwed the 4.5v of the keyboard somehow...

Has anyone else ever had experience of something like this happening to a bent instrument?

I just hope the thing doesn't gradually die on me coz I'd just got it finished!

[Bogus Noise]

What kind of clicky noise are we talking about? Is it related to the speed of the 555, random noisiness, or a single click at the beginning of each note?