Hello,
one of my old Topcons has given up recently. During shutter action a really strange "springy noise" could be heard. Since then the mirror has been stuck in the top position and the advance lever can't be moved by more than a few millimeters.
Initial investigation revealed the shutter button behaves like the camera is not cocked and the mirror can be forcibly lowered by pulling the short "mount aperture tooth" down. The DoF preview lever does nothing (as the mirror is in shooting position). That's about it.
I got myself the service manual and successfully unmounted top right front and plates - I've even obtained a 1.4mm "holding" screw as the manual instructs. However, under the top right plate, there are no excessive dirt/dust particles nor loose parts in sight.
At this point I'm quite scared to continue disassembling since I got no clear idea what subpart should be inspected next. The service manual doesn't seem to describe of such issue so I'm out of ideas.
Do the symptoms sound familiar to anyone, please?