brand new engine lockups

[bubkiss]

 :-[HI, I have bought three expensive engines new in the box, and all of them are locked up. one is a forney, one is a 4-4-0, and one is a 2-6-0. no matter how much power you apply in either forward or backward the engines won't move. if you thy to turn the drive wheels they are locked up. can somebody please help me? I have already sent another engine back to bachmann and they charged me 50.00 to fix it. I don"t want to spend 150.00 to fix them. thank you in advance for any help you can give me.