I have a Yamaha PSR-S700. Recently, the touch sensitivity in one of the keys stopped working. Very little pressure applied would cause the note to sound as if the touch sensitivity was off completely. Now the key has stopped working completely and the action feels different to the other keys. The keyboard has never taken any knocks or been damaged in any other way. The key in question is an 'A' key which is commonly used, but no more so than many other keys. Just wondering if anything can be done about this problem. Thanks in advance for your help.

You MAY be confusing touch sensitivity with VELOCITY sensing. Touch sensitivity is PRESSURE put on AFTER the note sounds that causes modulation. VELOCITY is what is used for example to control the loudness of pianoo notes depending how fast they are struck. VELOCITY sensing is done by using TWO contacts at every key... one closes first. IF one of these gets dirty, FULL velocity will be sensed and it will be LOUD. The contacts can be cleaned using ONLY 99% isoprophyl alcohol and Qtips after MUCH disassembly of the keyboard. The contacts are conductive rubber pills in silicone rubber domes. Clean boththe contacts and the circuit traces they pres down onto.