What generally happens as these Yashicas grow older is that the white wire going to the bottom of the battery chamber either gets corroded or actually breaks at the connection. It's an easy fix if you're handy with tools. First remove the bottom plate and check out the battery chamber; see if it's corroded. If in question remove two phillips head screws that holds the battery chamber in place and pull it out to check the white wire soldered to the bottom. It may not be broken but it may not be making a good connection to the battery chamber. If you have a test meter, check across the battery spring inside the battery chamber and the connection to see if you have continuity. If not, resolder the wire. I've had to do this on 3-4 of my Yashicas, and generally speaking this will cure the problem.