LCD Display of Digital Piano Keyboard: Common Issues

Hi, LED indicators on Electronic Piano Keyboard Question: I bought a second hand keyboard and used it only one time. Then we had an overloading. We replaced all circuits but in the main circuit there isn’t a 5V input. The speakers are working, however sometimes the display is on, but the system cannot turn on. No LED indicator light and keys are not working. I showed it to several keyboard specialists but they can’t fix it. We don’t want to throw it because this keyboard was quite expensive when we bought it. Any suggestions on what can we do now? We don’t have schematics. – by susan (Ráckeresztúr,Hungary)