a-pro 500 usb connection bad

Replacing that little connector probably isn't something you want to tackle yourself unless you're confident in your soldering skills. But letting a technician do it will still cost less than replacing the keyboard.
 
Another option might be to use the 5-pin DIN connectors instead of the USB port. That would only be possible, however, if you are a) using the optional wall-wart power supply rather than USB for power, and b) you have an audio interface with MIDI ports.