Camera video with images is here.
The camera was working on bulb (B) most of the time but not instant (I). The lens was in dire need of cleaning too.
This isn’t a complete tear-down. I didn’t open the viewfinder or remove the wind knob. This started just as notes for myself so there are some gaps in the images. I’ll try to fill in with text instructions.
Remove the lens ring inside the body. It’s a left hand thread. I couldn’t get a lens wrench past the film gate so I used a couple of small screwdrivers.
The lens ring also holds the inner copper (?) body. It won’t quite come out without removing the wind knob but it wasn’t necessary for getting to the shutter & lens.
The lens/shutter assembly comes out after removing the ring. The little screw is the Instant/Bulb selector. It didn’t need to come off but I didn’t know that at the time. The trim plate acts as a washer so it might be part of the lens distance as well as being cosmetic.
The lens surround is press-fitted to the shutter. A gentle squeeze to the shutter body near the I/B selector (there’s a little bump out on the shutter body) while pulling with your thumbnail near the shutter switch will pop it off.
There’s the culprit. The spring had come off of its post. Sitting there without tension for however many years may be why my shutter is fast. If it didn’t need cleaning (and if I wasn’t curious) I could have put the spring on the post and reassembled here.
The I/B selector screw screws into this springy copper bit. The springy bit provides friction so the selector doesn’t flop around. The end of the screw blocks the spring post on the inner (brass) shutter to provide bulb.
The big brass screw holds the outer shutter and the outer shutter return spring. The upper part of the spring presses against the shutter body and the lower part presses against the edge of the outer shutter blade (the black part). See the previous image for its proper location.
The copper springy bit. This is reversed from how it goes in. The round part goes in first toward the back of the shutter body, away from the lens.
The inner shutter pivots on this flatter brass screw. It has an unthreaded part that acts as a spacer and shaft for the shutter.
With the inner shutter removed, you can see the aperture. It’s held in with the small brass screw.
Finally, all the way to the bottom. The screw also acts as a spacer for the aperture. That’s some quality blackening on the aperture.
Not shown: 1) Cleaned the shutter parts. I used cotton swabs and lighter fluid. 2) Re-blackened the aperture with a permanent marker. 3) Cleaned the lens front and back with lens cleaner. I doubt if it is coated so window cleaner might be OK.
I tried pre-fitting the inner shutter screw but I couldn’t seem to get the screw lined up with the hole in the aperture.
Instead, I used a tapered lens wrench piece to line up the aperture in the inner shutter and the aperture and then inserted the screw.
That’s pretty much it. Do the steps in reverse to reassemble. Before I put the lens/shutter assembly back on the body I did shutter speed tests.
This is a sequence of stills from a 240 frames per second video. I did about 12 shutter tests. Shutter opening didn’t vary much – most were open for four frames.
1/240 frames per second = 0.004166666666667 seconds per frame (~4.2ms).
Open for 4 frames = shutter open for 0.016666666666667 (~16.7ms).
Turn it into a nice shutter speed style fraction: 1/X = 0.0167. X = 60.
If I’d been thinking, since 240 is a multiple of 60 and 4 and the shutter was open for 4 frames, I could have just done it in my head. Duh.
In my defense, I do this for a lot of old, slow shutters and it’s rarely this clean.