I have a friend who has a Yamaha psr740. This thing has to be over ten years old. That was my first keyboard. There are three keys in the uppermost octave that have stopped working. Not producing any sound. I recall seeing some thread on here about this over the years but a search did not reveal anything. Anyone know... can a layman possibly fix this? It wouldn't be worth spending much money on such an old keyboard.

I don't have an arranger anymore. Thinking about all this stuff, might buy a used one again and dink around, lol. I have only played guitar for several years now.

Need to replace the strip underneath the keys. You can order it from Yamaha and it's not TERRIBLY difficult to do if you are handy with a screwdriver. Alternative is getting a technician to do it. Yammys are notorious for this. You could try taking the cover off, cleaning around the strip and being certain position is correct, but they do wear out.