Some older keyboards are not compatible with Roland and Boss D-Type sustain pedals. If you find your sustain pedal is causing modulation data to be sent when pressed, there are two ways to fix this:

1. Purchase a simple Casio, Yamaha type pedal. These all work fine with the keyboards.

2. The problem is solved by replacing resistor R6 on the main board with a 1K Ohm resistor.