Workshop facilities include space to have a full sized electric stage piano on our test bench for diagnosis.   We can obtain many OEM parts from the main leading brands including Korg, Yamaha, Casio, Technics however sometimes as pianos extend past 10 years parts do start to become obsolete.  We typically find faults are where they interface to the outside world, this includes broken and intermittent keys.  Headphone jacks being broken and power cable issues and sockets.  Typically pianos in excess of £400 in value are worth repairing.  Our costs are higher for piano repairs due to the complexity of the cases and how much they have to be taken apart to get to the parts.  The longest it's taken to get to a component on a synth has been 3 hours and about 200 screws! But usually electric stage pianos have a minimum of 20 screws to separate them!