How do I diagnose a xm1 thats not turning on?

I know this is a very old camera, but its a beautiful 1. I managed to get my hands on a xm1 in mint condition for 150 euros. After a while of using it it stopped turning on. I am not really experienced in diagnosing electronics, but i gave it a shot. I took the camera apart and started trying things out. I found that the camera gives a reading of 0.3 volts without the battery inserted, and 8.25 volts with the battery inserted. However nothing changes to the readings if I use the on and off switch. I hope somebody can help me with this issue.