I have a CP-33 in the shop with slightly sluggish action. The keybed is clean, all joints are well greased, and the grease is not drying up or gunky. The key return springs are slightly bent in the middle, but I am pretty sure this is normal. The replacement springs description says, “Key return flat springs”, does anyone know if the spring is actually flat? Or is this referring to it being a flat piece of metal? If they are indeed flat and not curved, that would produce more key resistance. Any help is appreciated, thanks.
Those springs are very nearly flat - they have a slight curvature when removed. But usually sluggish keys on these keybeds are not a spring issue - it is usually caused by a small crack at the back of the key itself, which then causes the key to sit slightly cocked, and thus not travel as smoothly as it oughta. So I would take a close look (perhaps with a magnifying glass) at the back end of each troublesome key, and see if you can detect a crack where it snaps into place on the chassis. In the rightmost key in this photo, the cracking would occur at the small tab in the lower left corner:
