Unfortunately this story doesn’t have a happy ending – or at least it doesn’t have a happy ending yet.
Having got the light seals replaced and the mechanism on the mirror box all cleaned up and lubricated I continued to see if I could work out why the shutter would cock but not fire. I decided that I might get further if I re-assembled the shutter into the camera chassis and tried fitting the front of the camera on again to see what interacted with the shutter and see if I could work out the sequence.
So I fitted the shutter back in and carefully refitted the lens mount/viewfinder unit. With it in place and the linkage at the bottom of the camera replace, I wound the film advance and was pleased to see that the shutter blinds correctly moved from the bottom of the shutter to the top showing they were cocked. When I pressed the shutter however the same problem as I had originally occurred: the mirror flips up but the shutter doesn’t fire.
The shutter should start to fire when the mirror had reached the top of it’s travel, so I tried finding a lever or control arm which should be interacting with the shutter to get it to fire, and I think I found where that is supposed to happen. I removed the front unit and the shutter again and once again tried to see what the problem was. And that’s when I found that a small spring, which should hold one of the wheels under the speed selector in tension, had come off the point where it’s meant to hook. It’s position is quite difficult to see and I’m fairly sure that it is the reason the shutter isn’t firing. The wheel which isn’t in tension, and therefore isn’t moving, seems to initiate the opening of the first shutter blind.
I think it probably means this shutter is not repairable – at least not by me. My eyesight is not good enough to be able to hook the spring on (I can’t actually see where it fits!) and I’m sure I won’t be able to strip the shutter down and repair it, so I think the Singlex will need to wait until I can find a donor camera which can give up it’s shutter 😦
Still, it’s been fun trying to get it fixed, and I certainly fix more cameras than I can’t fix so I’m not too disappointed.
I’ll reassemble the camera and wait until I can find a beaten up Singlex TLS with a good shutter unit.