----- Original Message -----
From: "P�l Jensen"
Subject: Stiff aperture rings
> I've noticed that the aperture rings on my A 35/2.8 and A
24/2.8 are getting progressively stiffer. You almost need to use
force on the 24mm. Is this "normal"..any remedies...
I've had that happen on a couple of lenses. Unless you are
mechanically gifted, send em off for repair. The lubricant used
in the aperture mechanism does dry out over time. I have
successfully fixed this problem on M series lenses, but the only
time I tried to fix an A series, it blew up on me. I still have
some of the parts on my desk, but I fear the poor thing will
never work again.
Collin Brendemuehl posted this a while back. He gives very lucid
instructions for the procedure.
Aperture Ring Maintenance.
Precautions: Clean, flat area to work. Preferably not above
carpet.
Additional tools: Large plastic bag, magnet.
Often the aperture ring will be jammed or jerky because
1) a spring under the "A" button is broken
2) the ring itself is stretched from use
The aperture ring has a "slot" location on it where,
when reached, frees the "A" pin. It can easily fly out
when reached.
The "A" pin component is actually 4 parts:
#1 Spring
#2 Pin
#3 Base, sits under the spring and has a tab that
extends inward to the interior of the lens.
#4 Brace, the pin slides in place on this tab. Its arm
reaches
down into the aperture ring where a tab keeps it from
coming
out until the ring is turned to the release point.
Removal of the aperture ring can be accomplished by:
Step 1: Turning it until the pin/spring assembly comes out.
It may fly out. You may want to do this inside a
plastic bag
with a magnet present to catch the parts after they're
released.
Step 2: Lift the ring off. You may encounter some resistance
in various
positions. Turn it carefully until you reach a place
where it
lifts off easily.
Underneath the ring is a small bearing that hits the detents for
the
aperture settings. This bearing can be easily misplaced because
it
usually has a good amount of grease on it. Keep track of it,
and the
spring behind it, should there be a lack of grease and they fall
out
when the unit is disassembled.
Also be certain to keep track of the "A" button. It's also
easily lost.
If a spring is broken, it can be repaired by:
(a) 1) Drill out the spot where the melt mount dislodged
2) Fill in the hole with a small piece of plastic
3) Melt the plastic into place like the original.
(b) 1) Drill out the spot where the melt mount dislodged
2) Screw the spring into place with a tiny screw.
--This may be difficult to find as it needs to be
fairly flat and fit under the aperture ring and
still allow it to turn freely.
Reassembly:
When reassembling I use a thin piece of paper or Scotch tape on
the
detent bearing and springs so that the ring does not push
against them
and they break free or spring free and get lost.
Slide the aperture ring into place with the "A" pin notch in
place
for remounting the pin assembly. Be certain to pull out your
paper/tape
spring and pin holders as needed so that you don't have extra
material
inside the ring.
"A" Pin replacement:
Then, with a tweezer put the base in place under the
"A" pin spring location.
Next, set the "A" pin spring into place.
Then, holding it down with your finger, turn the aperture ring
to lock
it into place.
RECOMMENDATION: THere's enough broken old 50/2 lenses out there
for
nothing, or a buck or two. Get one and experiment with it.
You'll learn and have spare parts that you may need for the real
repair job.
(Like springs and bearings!)
IDEA: If you want to make your camera Really Versatile, leave
the detent
bearing out. You'll have continuous aperture, just like those
TLR and LF
cameras! (Might be fun or useful to do with that second, extra
lens.)
Collin Brendemuehl
William Robb
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