Neither adaptor nor batteries will power up my keyboard. I suspect a TO-220 package 3 lead transistor.its labeled BI342 but cannot find this anywhere.Any ideas where to troubleshoot?
It's probably a 2SB1342 bot a BI342 often the prefix is ommitted and that I is likely a 1. The 2SB1342 is a TO-220 pkg. and it's specs are here: 2SB1342 Datasheet
What makes you think it's the culprit? Is it obvious by looking at it?
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.