Failed action while the Self Timer was running, resulting in the Self Timer stopping before the end of its run, and the shutter not working.
This also happens to be the normal position of the Cocking Rack after the shutter has been charged. Just to the right of the rack knob lever at the top of the shutter barrel you can see the Stop and Catch for the Self Timer position of the rack. This has to be manually depressed to let the Cocking Rack go into the Self Timer position.
Compur Shutter Failure 2 by P F McFarland, on Flickr
1) B Hold: Did not retain the B Lever.
2) B Lever: Fully released, allowing the Shutter Trip Lever to return to the start position.
3) Shutter Trip Lever: Did not keep the Catch clear of the Cocking Rack.
4) Catch: Was allowed to hook the first notch in the Cocking Rack, stopping all action, and resulting in a total failure of the shutter.
Normal action while the Self Timer is running. (The toothpick is there to freeze the action)
Compur Shutter Failure 4 by P F McFarland, on Flickr
1) B Hold: In proper position to retain the B Lever in a mid position until the Self Timer runs off.
2) B Lever: Keeping the Shutter Trip Lever from returning to its start position, and holding the Catch open.
3) Catch: Being held away from the Cocking Rack by the Shutter Trip Lever, so the Self Timer can complete its run.
B Hold lever parts.
Compur Shutter Failure 5 by P F McFarland, on Flickr
1) Retaining Screw
2) B Hold Lever, underside
3) Tension Spring, broken off.
NOTE: The shutter will operate normally without the B Hold being in a working condition. However, if the Cocking Rack is ever moved to the Self Timer position, the shutter will fail, locking up the action.
There's a couple more photos on Flickr if you're really interested.
https://flic.kr/s/aHskniAu9Y
PF
