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The power supply is a 12V adapter... the circuit board where the power enters, has several caps, resistors, and this transistor together with a smaller one. When I hold the power button on for a while this transistor warms up. The only thing that happens is a barely audible thump through the speakers. The LCD on the keyboard doesn`t get any juice.
is the LCD display backlit? or is it completely out without even segments? can you measure voltage on other board locations that may have marked voltages on it? If so the power supply isn't the issue. Often board connectors will be labeled as to each pin's function. Look for 12 volts and or 5 volts dc. for starters.