Have you tried the battery check? In case you do not have the manual it may not be clear how to do it. Set ASA to 100, shutter speed to 1/2000 and turn the spring loaded rotary switch on the left shoulder; for a new battery the needle in the viewfinder should rise to the index mark. If it doesn't and the contacts are clean, the galvanometer is dead or there is a dry joint. This would not affect this test, but note that the current PX625 is the wrong voltage, 1.5V, when the camera is designed for the original 1.35V battery. The Wein zinc air cell provides the correct voltage. It is also possible to use a hearing aid battery in an adaptor.