dehydrating prpblems

I have an Excalibur 9 tray dehydrator. I got it mainly because so many on forums like this were saying how good they are. I needed to get serious about my preps so I sucked it up and bought one. I must say that I've had limited success with it. Either I'm not doing it right or that's just the...

I have just a basis 4-5 tier dehydrator. When i try to dehydrate banana's or strawberry's even if i cut them large they shrivel to nothing. the banana's turn mostly dark brown/blackened. It seems to do apples, oranges, pineapples okay. any suggestions on how to do better at banana's? my...