SA 46 might be a Casio keyboard. If so the manual at the following link indicates that it uses an an external tethered-brick style AC/DC 9.5VDC adapter to run off mains AC power.
Use a multimeter to determine if the adapter is outputting close to 9.5V. If it is, which seems to be the case based on the initial post, plug it into the keyboard and measure whether it is maintaining 9.5V, which may require partially dismantling the keyboard.
If it maintains 9.5V, trace the circuit to see where the power stops. The problem might be something as simple as the power input socket having a broken solder joint. If that is the case, determine if the copper trace to it is intact or whether it needs glued down or a jumper wire and possibly epoxy used to fit the socket in place and complete the circuit to the next point along the trace.
http://support.casio.com/pdf/008/Web_SA46_47ES1C.pdf