The simple solar dehydrator is a sheet of roofing metal or plastic with food on it, drying in the sun, but I am assuming you want a dehydrator that protects the fruit from UV or insects or which can function without your input during rain showers.
About 15 yrs ago I made one. It worked well in Nova Scotia in the summer for apples. The inovative thing about the design was to have the air moving down while doing the drying. This had been proven more effective in design trials.
So here is what you need think about when building it:
Fruit sits on a non-reactive screen in a frame. If you already have framed fiberglass mosquito screens, you are on your way.
These frames sit one above the other in a drying cabinet. (put door on front so you can slide screens into place)
Hot air enters cabinet at the top and exits at the bottom. (chimney needed to pull cooled air out)
To get the hot air, build a long, shallow box, the same width as the cabinet, open at the top and 2 short sides. Paint bottom and sides flat black and cover with a window or clear plastic.
Leaving out many details (like how to hinge doors or keep out insects), so you can see the basic idea without being overwhelmed with info. Please let me know if the basic idea is still unclear.