Why isn’t yamaha improving the power supplies for these keyboards ?
Because most power supply failures are the user's own fault. Wrapping the cord around the power supply's "brick", when it is not in use, is the number one killer of power supplies - in either of two ways. The sharp edges of the corners of the case kink the wires, inside the insulation, over an over, and finally cause them to break - like bending a wire back an forth until it breaks. Most user's who do this also bend the cord at a sharp 90 degree angle where it comes out of the case, and cause it to break there. Then there are the folks who treat the power supply brick as though it is actually just a brick and drop it, throw it, or what have you. I continually see threads on forums by users who think a power supply is a power supply is a power supply, and in a pinch, will connect any ole power supply to any ole device without ever checking voltage and wattage specs to make sure they match.
Like andyg, above, I have been in this business since the mid-80's, have had many keyboards, laptops, and various peripheral devices over the years, and have never experienced a power supply failure. Yes - some power supplies do fail, but if the situation were as bad as you state, andyg and I both should have had several by now.
