Only do this modifications if you know what you are doing. I will not be responsible
for damage done to you, your device or the people around you.
For an installation called Boom Boom Station, we chose several cheap and easy to play instruments like the Korg Monotron, a delay line from behringer and a stylophone. To save money and battery-induced environment pollution we opened the Korg and the Stylophone to add extern power, so that they can constantly driven with a standard power plug.
The input can now come from any power supply (6-20V), the output goes directly to the Monotron: as you can see on the pdf schematics which Korg was kind enough to release, there is a 5V PIN already set up at the circuit board (middle left “VCC +5V”). In the standard circuit the 3V from the AAA batteries of the Korg are amplified with a step-up converter to create the 5V needed to run the biest.
To ensure that you don’t destroy the valuable Korg, you can add 1N4004 Diode, to protect the circuit against reverse polarity (like in the circuit above).
Here is the Korg schematic again:
Same goes for the stylophone. In the standard use it is powered by 3 AA batteries, creating Voltage of 4.5V. The 7805 power regulator outputs 5V, but hey – +0.5V lets the stylophone only run faster! It works.