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Old 21st May 2013, 08:20 AM   #1
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Default Need help starting keyboard mod project

Hi Everyone,

I am starting to get into some keyboard modding and I wanted to see if anyone could help field a few of my questions (these seem like they would be very basic, but I'm having trouble finding information that is specifically helpful to me). I'm in no way an expert when it comes to PCBs so I apologize in advance if these questions offend you with their stupidity.

First off, I have a fully functional, but slightly busted up, Williams Encore keyboard -- pretty nice, but nothing special. I just bought a new Casio Privia as my main keyboard, so I wanted to do something fun with this old one and use it as a MIDI controller. I'm not entirely sure what I want to do with this thing yet, but I have a lot of ideas: however, I want to find out more about the reality of the situation before I get too excited. I'm thinking I might attempt to strip it down to the keybed board and try to take some of the weight out, and customize the keys a bit. Or if possible, plug in an entirely different raw data source to the main board instead.

I've mapped all of the cables from each of the boards to each other. Pretty straightforward. I understand where the data is coming and going at least. My most important fundamental question is, how interchangeable or "standard" are these parts usually?

For instance, does the 11pin ribbon cable coming from the board in the keybed (which I imagine carries the raw MIDI keystroke data), which plugs into the main board have any chance of interfacing with a different main board? That cable is the only connection between the keys and the rest of the system, so I assume the keybed draws power from it as well. What is the potential for plugging in a different keybed? Or is the reading of the specific input layout of the keys only possible from a mainboard designed for it?

This goes for the mod and Pitch bend wheels (each are connected to the input board via 3 wires), Volume/Soft/Sustain Pedal inputs, and control panel as well. Is there any reliable way (without a complete design schematic of the thing) to determine, or at least educatedly guess what raw data is being sent back and forth so I can determine dependencies among boards (i.e. is the sound board going to fry, for some odd and incomprehensible reason, if I pull out the mod wheel and power it up again). I feel like assuming that everything in the system is inextricable and complete must go against some core DIY mantra, but I don't want to rule it out.

Another thought is that I wanted to maybe pick out the amp & speakers (decent quality, and loud) and inputs/outputs, and somehow make a small monitor to connect to my Privia (which has no speakers). However, the 12v in from the dc adapter goes through the amp board and what looks like a 9v out into the main-board etc....if I unplug the rest of the keyboard from it, will i have to reduce the source of the power accordingly?

I can diagram the wiring out for anyone who is curious, or can just put up pictures. Feel free to attack as many or few of those questions as you want to. As I said, I'm just narrowing down what is possible, so feel free to tell me what isn't. Thanks!
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Old 21st May 2013, 05:36 PM   #2
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Location: Jeffersonville, Indiana USA
Well, this is true do it yourself, you are way out there.
Taking the keys out of the casio and running them somewhere else is technologically doable, IMHO. but you will have to figure out what matrix diode scheme they are using to multiplex the keys, with a meter. Hint- very early keyboards used a 8x8 matrix or 8x6 matrix, but this caused a lot of problems. Most keyboard matices after 1980? used a 12xX scanning layout.
Building a separate amp for your newer keyboard is a different project. I suggest an IC amp, like a LM3886. See various vendors in the below forums for PWB's, chipamp.com advertises via google on diyaudio, I don't know how good they are but the name is easy to remember.
As far as salvaging the tone generator parts of the casio and dumping the amp part and power supply part, you will have to measure the voltage going to the tone generator part when it is still working, and make sure you replicate that voltage when you design your own power supply. If you can't find a wall transformer with a suitable supply (Salvation Army has a whole bin of them near me), then read Thomas Floyd Electronic Devices the Electron Flow Version about power supply design and test. It is an old community college textbook I found at Goodwill.
Something not usually doable, is remote mounting the mod and pitch wheel, and the various control buttons, away from the Casio computer board. The microcontroller IC tends to do everything in modern packaged music systems, and putting extended wires on these input functions transmits RF interference to the microcontroller, which tends to drive it nuts. Replacing this board gets into microcontroller design, which is beyond my skill level at this point (although I was pretty good with an Intel microcontroller development system back in the days of the 8080). People tend to use ardino, PIC, and Rasberry microcontrollers these days, but there are other forums that are better for messing with these than diyaudio.com.
I tend to monkey more with old organs, which are totally analog, but that is a different subject. I like the Hammond H100, it is practically a sine wave synthesizer hand wired, and hundreds go to the dump every year because they don't sound like a B3 without replacing 71 capacitors. Modifying old hand wired analog organs is a hobby limited to North America, UK, Anzac, and maybe Germany, as old junk analog organs are thin on the ground in other countries.
Good luck and have fun.
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Last edited by indianajo; 21st May 2013 at 05:42 PM.
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