B speed not working on Fed-2

[fanshaw]

I have a Fed-2 which has a shutter that seems to fire at 1/30 when set on B. I took the top off and it worked OK. When I replaced the shutter speed dial the fault re-appeared. It seems that the extra weight of the dial was enough to stop it working as it should. If I brake the dial as it turns, by letting it rub on my finger, the shutter stops open as it should until I let go of the shutter release. Is this due to wear somewhere in the shutter mechanism? Can anyone suggest a likely cause?

 

[fanshaw]

No, I noticed the fault when I got it and I want to fix it first.

 

[wolves3012]

Have a close look at the crescent-shaped arm that sits under the speed dial (roughly speaking). It's that that controls the proper operation of "B". It should be lowered when you press the shutter. When lowered it traps the second curtain. On other speeds it gets pushed aside after the set interval, on B it's held until you release the button and the arm rises again. It should be under pressure from a small spring which pushes it downwards and inwards.

 

[fanshaw]

Thanks Wolves and Pixtu. The arm and spring are in place. Thinking about it again, one possibility is that the tang (if that's the right word) that is caught by the arm and detains the second curtain is slipping past the arm sometimes. Perhaps if I try bending it upwards it might cure the problem. That looks a better bet than trying to bend the arm, which is obviously meant to be flat. It seems that I am answering my own question, but I thought it worth asking if anyone had solved the same problem.

 

[wolves3012]

It must have been fidget that did the drawings since it was not me. It's worth making sure the step in the arm is "square", where it traps the second curtain. If it's worn rounded then a little careful filing can restore it.

 

[fanshaw]

Thanks again, Pixtu and Wolves. I shall have to try bending and/or filing the arm.