I have an older manual flash that connects via the PC Sync port (the trigger voltage is 6v so it is safe) so when I plug it in and take a photo, the flash does not fire. The test button fires the flash so I know the bulb is ok. I have also tried the pc sync to hot shoe adapter on a couple of Nikon cameras and it still does not work. Is there a menu setting on the camera that I need to set for manual flash mode? I know there is a setting for manual lenses is it the same for a flash? Thanks!