Hacking the Yamaha PSR-300

May 22, 2014 – 11:29 am

For one of my projects, I needed something to generate notes from MIDI data. I looked at eBay, and there were MIDI sound modules on there, but they were going for £40 upwards. I thought that there must be a way of doing it more cheaply.

So, I started looking at musical keyboards. Companies like Casio and Yamaha make lots of different models of keyboard which have MIDI in and out ports. Since there are lots of these out there, they tend to go quite cheaply on eBay, especially since they are difficult to post, so they tend to be collection-only, meaning that the number of possible rival bidders is much lower.

Anyway, to cut a long story shorter, I ended up buying a Yamaha PSR-300 for 99p.

Opening it up, it turns out to be a really good candidate for what I wanted, since the circuit board is only 4.5″ by 10.5″ – quite small for a keyboard.

Yamaha PSR300 Circuit Board

For my project, the only button I needed was the on/off button, since I could set the voice and play notes purely by sending MIDI data. If you look at the circuit board from the component side, with the MIDI sockets at the top, the power button is connected between the 2 right-hand pins of the white 14-pin connector.

Yamaha PSR300 Power Button

For sound output, I cut the speaker cables, and attached connectors so I could wire up my own speakers. I decided to keep the volume control as it is, but you could always wire up your own instead.

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