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Recently my midi keyboard was damaged and it is not powering on, But now I realize I don't really need many features including speakers of the keyboard. So I thought I can convert into a small portable midi device. So the circuit in the image is the one which is giving midi output. Also this is the only one circuit the keys are connected to. So if I can power that circuit up I think it is going to work as a midi device, How to Power up only which pin should I connect to GND and power source, also how much voltage, Where can I find these details of a circuit board. The modal of keyboard is CASIO CTK 3000, and what are the precautions I should take. Also How can I power up the circuit with a USB cable from my laptop(if possible) The 13 pins at the bottom of the image are the one, which is connected to the other board wich takes power input Here is the Circuit Board which is giving midi output

enter image description here

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  • \$\begingroup\$ Find the schematics for the device first to know how to start modifying it. \$\endgroup\$
    – Justme
    Commented Sep 16, 2020 at 9:30
  • \$\begingroup\$ It's unclear exactly what you are asking. Repair questions are off topic. If you wanted to rip out the electronics and substitute something else that is possible but not advisable. The entire project is too broad fit a stack exchange question, though a very specific part of it once you have done research on what is needed and have an overall plan might fit. But again it is not really a worthwhile project - too many keys to wire up, likely poor results. There are also previous questions here about aspects of such attempted conversions. \$\endgroup\$
    – Chris Stratton
    Commented Sep 16, 2020 at 14:45

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I'm unclear on whether you want to make your CTK-3000 into a MIDI controller, where the keyboard would generate MIDI signals to control other instruments, or a MIDI module, where the device would generate sound based on incoming MIDI messages. Either way, this seems like it would be a long project.

I could not find any technical data on the CTK-3000 keyboard, but I did find a service manual for the related CTK-2000 keyboard at https://manualzz.com/doc/1881381/casio-ctk2000-service-manual . The models share the same user manual, so they are likely very similar, but you'll want to look at the layouts and schematics carefully to see where your keyboard differs.

Looking at those schematics, I can tell you that converting to USB power could be hard to do. Part of the 9VDC power from either the wall wart or the batteries is converted to 5V to run various ICs -- and some of that is likewise converted down to 3.3V -- but it looks, from my quick look, like there are some parts run off the 9V natively. I don't know if those parts are the ones you want to keep using.

Good luck to you.

EDIT: After looking over the CTK-2000/3000 user manual and the CTK-2000 service manual that I linked to, I think I found the differences in the two: on the schematic, where there are portions labeled "Not used", those are parts that are in the 3000 and not the 2000. So these should be complete schematics to your keyboard.

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  • \$\begingroup\$ Main PCB M800-MDA1 (page 22) this is the one I want to use. I want to use the keyboard as a device which only need to generate midi signals when a key is pressed, I don't want to convert MIDI signals into sound, I just want the midi signals to come out through the USB port which is in the above mentioned PCB. How can I understand the use of each pin among the 13 pins on that PCB? some of them must be for giving the input dc voltage. I think If I can connect those pins to a source I will get signals from USB output. pins are named(MIC,PEDAL,ADIN,MUTE,DG,APO,VC,VA5,LOUT,ROUT,AG,BEND,VD3).Thanks \$\endgroup\$
    – Sandeep S J
    Commented Sep 16, 2020 at 13:40
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    \$\begingroup\$ From my understanding of the schematic, VC is +9V, and DG and AG are ground. VA5 is actually an output of 5V from a converter on this board, and VD3 is an output of 3.3V from another regulator here. So putting +5V to anything on that connector won't work. What could work is wiring a jumper from the USB port's VBUS (at the ungrounded side of C75 -- see page 7, bottom view on the left) across to the output of IC5 (which is its pin 2) -- on the same side, between FU2 and C84. The schematic suggests that the digital stuff only draws 130mA, which should fit in standard USB's 500mA limit. \$\endgroup\$
    – Taper Wickel
    Commented Sep 16, 2020 at 18:27
  • \$\begingroup\$ (I want to stress that this is my understanding of the schematics, and that this is pretty delicate work -- I believe it should work, but I don't have proof, and it'd be really easy to mess something up with this. You should also completely remove those CN3 connections, to make sure that the power supply/analog stuff board isn't trying to partially power on and messing things up. Good luck!) \$\endgroup\$
    – Taper Wickel
    Commented Sep 16, 2020 at 18:29
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i don't know if you still want to do this mod, but i just did it. I managed to take the whole top part, and just leave the keys only. I had it like that for a month, and then decided to start looking for ways to remove completely the LCD board, and the power ON & Volume board as well. I did it by just removing the LCD board completely, and also the power switch board by desoldering all the cables.

It's only soldering two pins in the power supply board together

AND bridging with a 2 wires cable the pins as i draw on this Manual Service PDF, look at page 22 and 23. That's it. Only thing missing is the power switch but you can manage to add one, i didn't need it as i need the keyboard turned on always and i have a surge protector so i don't mind that much

There you go, enjoy!

PDF with drawings on where to solder what:

https://drive.google.com/file/d/1mrGx7RRyUG_X9heFgEng9REZitL0Nrqy/view?usp=sharing

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