Artboy
Joined: 04 Dec 2018
Posts: 20
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 Posted: Sat Oct 05, 2019 4:08 pm Post subject: |
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Artboy wrote:
You can try to DIY it:
Part 1: The Focus & Release Assembly
Remove the release button with four screws. Can lubricate this unit without further disassembly. Clean and
then graphite lube. Be sure the action is smooth, and reassemble.
Focus to infinity, set to f/4, and mark the way the lens should rejoin before separating. Mark the position of
the top of the focus barrel at infinity with a line on the aperture ring. From the back of the lens, remove the
thick spanner ring (thickest and furthest outside of the 3 visible spanner rings).
If this spanner ring is too tight the auto aperture mechanism will bind and not close down, especially for
wider apertures (may have to back off later). The lens will come apart into 2 main components, the lens
assembly and the focus/release assembly. A spacer ring around the lens assembly is loose and can fall off
the assembly (an important item for attaining precise infinity focus later).
Observe the release/focusing assembly, with the inner helical ring in place. Note that the cocking
mechanism moves a quarter circle (running from about 10 to 2 o’clock in the above photo), then pops out a
pawl. On release the pawl pops back in.
Don’t perform the following separation if at all possible. To separate the release assembly from the
focusing assembly, remove the focus stop screw, a large black pan head screw inside and screw off the
focusing assembly by turning counterclockwise—the helical drives up until it dethreads (when it is
approximately flush with the top of the focusing assembly), and then you continue unthreading the focus
assembly from the release assembly. So, two sets of threads were unscrewing, and then just one. Even
though the helicals will rethread in many ways, those helicals must go back together with particular threads
meshing with their matching grooves. You’re in for hours of trouble trying to get the helicals back together,
and timed correctly with the focusing mechanism.
So you separated them anyway. Another spacer ring (silver side to front) will fall out of the focus assembly
if you invert it (likely also important for precise infinity focus later). The shutter release assembly is still
operational. Clean the mechanism and buff the aluminum at this point. Don’t allow any protrusion to catch
while buffing! Cleaning the cocking mechanism leaves it unlubricated and gritty feeling—relube it without
further disassembly by forcing your lube in.
As mentioned, the inner aluminum helical will (reverse) screw up and out when it gets flush to the top of
the focusing ring. It can be painful getting it back together, so clean and lube it. After experimenting with
Molykote and graphite I switched to Nyogel 701 which worked pretty well. Probably should use NyoGel
Helical 744 if I had it. The helical will screw back in (with effort and patience, and from the top, not the
bottom). Note that the helical pushes out toward the front of the lens as you turn the lens to closer
distances. On reassembly, the rear of the focus assembly should almost hit its stop in the back of the release
assembly. That’s your best indication you got the appropriate meshing of the helicals.
The trick is to set the inner aluminum helicals at a certain point and then use the spanner wrench to hold the
inner helical with its two grooves matching and meshing the upright posts on either side of the inside of the
release assembly, while you turn the outer focusing ring clockwise to screw the helicals on and down. You
can see the rigid posts (at 1 and 7 o’clock) and the rotating aperture cocking post (at rest at 8 o’clock) in the
next photo.
Here’s the trick to reassemble the release and focus units: you have to reassemble the release unit and the
focusing unit WITHOUT the inner aluminum helical tube in place. Screw the focusing unit on all the way
(clockwise) until it stops, and then unscrew it a scootch so the index mark matches infinity. Using this as a
reference point, unscrew the focusing ring one full turn plus a little (go past infinity to the 2.5 meter mark,
which is a point a little more than one full counterclockwise turn from your reference point). Now drop the
helical tube into place, aligning its two grooves so they will mesh with the release unit’s two alignment
posts, and keeping the aperture cocking post within visibility at all times (you can see a special cutout for
its action at the bottom of the helical tube). The helicals are reverse threaded, so nudge them CCW. Just
start to screw the helical into place (a fraction of a turn, just where you hope it will start). Now place your
spanner wrench in the slots of the helical tube which accept the posts, and “focus” the focus ring down
(clockwise). If all goes well the helical tube will catch its threads at precisely the right point but your
spanner will keep it “stationary” as the focusing ring turns clockwise. You will likely repeat this step
several times. It helps to put your spanner in a vise so it acts as a third hand. If the helicals started at the
right place, the rear portion of the focusing unit should just meet its stop point at the rear of the release
assembly as you approach the infinity mark. Now check to see if the focus stops (cutouts) are positioned
appropriately by viewing through the screw hole (the black flat head stop screw you removed earlier). The
cutout should stop as you reach the extremes of the focus ring (infinity and .5m) If so, put the focus stop
screw back in place. Whew! The big question is whether you got those helicals started at the perfect point,
so that the lens focuses correctly at infinity. May have to go back and repeat this procedure, experimenting
with points to either side of that magic “1 full turn plus a little more to the 2.5 meter mark” point. (Note: at
the 2m mark, the lens hits infinity focus too soon; at the 3m mark, everything looks good until you try to
focus at infinity, and realize it can’t be reached because the elements are not close enough to the film
plane).
This was a difficult reassembly; my helicals didn’t want to thread at 2.5m, but were glad to thread at 2m
and 3m. I finally marked the top of the helical tube at what would be infinity for ease of doing the
alignment, and kept on trying. At one point I thought I had success but I noticed the lens was hitting
infinity just a bit before the infinity mark was reached – and realized I had left out one of the two spacer
rings (the one that is around the lens assembly). Put it back in and it hit infinity exactly. So, it’s likely that
these spacer rings fine-tune the focusing setting (different dimensions used for fine tuning the infinity
focus, and when the ring around the lens assembly was zero dimension, true infinity came early at the 15m
mark).
To rejoin the lens assembly with the release/focus assembly at this point, there is a linkage between the
two. Don’t “straddle” the linkage units on each other, that’s not how it works. The grooved linkage of the
lens ass'y is moved aside by the cocking tab and caught by the cocking pawl. The linkage from the lens
assembly merely needs to be to one side of the cocking tab as it negotiates its quarter turn, to be caught by
the cocking pawl. Check to see that the infinity reference and the aperture reference line up. Thread the
“hefty” spanner ring back on by hand (to make sure it’s threaded correctly) then tighten with spanner
wrench. If the cocking mechanism binds, or if f/16 snaps down with much more authority than f/2.4, this
spanner ring is probably too tight, back it off.
One way to tell if the lens is sufficiently deeply seated in its focusing mount is this: On infinity, the space
between the front of the focusing ring and the back of the raised portion of the engraved aperture ring is 3
to 3 1/2 mm, depending on whether you measure to the base or the top of the raised aperture ring. (I
advised you mark this position at the outset.) If the lens is together wrong, that space will be wider.
Part 2: The Optical Assembly
It’s easiest to access the front 2 elements with the lens assembled. The Carl Zeiss Jena nameplate ring
screws off. Note where it sits relative to the shutter release (the ‘a’ in Jena lined up with the release on
mine). Now to remove the nameplate ring. After many unsuccessful attempts to unscrew it with various
aids, I had to place six drops of penetrating oil on the threads around the perimeter (deposit then immediate
wipe up) and let it sit a couple of hours. Then a rubber leg tip caught the ring and reversed it out, about 4
turns CCW. (Be certain that the rubber leg tip or rubber cork--or whatever--doesn’t touch the front element
of the lens!) Once the nameplate ring is off, clean away any penetrating oil. Now the front ass'y is ready to
come out – mark positions before unscrewing it, so you can return it to factory specs. Once the front ass'y is
out, remove the spanner ring around the front element – about 3+ turns and it’s off. (This ring was loose in
my lens, needed to be tightened down another 1/8 turn on reass'y). Now you have access to all the element
surfaces of the front lens assy. Go after them with 2 alcohol swabbings to get rid of the fungus. The front of
the aperture blades are also accessible at this point. I left them alone as they were clean. Reassembly of the
front lens ass'y is simple.
To access the rear lens assembly, it’s probably easiest to separate the lens ass'y from the focus ass'y first
(although not necessary). Now separated, unscrew the innermost spanner of the 3 spanner rings visible
from the back. The rear lens element will fall out. Immediately mark it for direction; it’s curves are subtle
(the moderately convex side faces the back, the flat side faces forward). You also have access to the back
surface of the next highly convex lens element inside; leave it in place if you can. Clean these and
reassemble. On reass'y, check infinity.
Final infinity adjustments: Infinity focus can vary after a mere disassemble/reassemble of the main assy’s.
On one reass’y, infinity was perfect. On the next, it arrived early at 15m, indicating that the elements are
further back than they should be. Hitting infinity correctly is controlled by the spacer ring that sits around
the lens ass'y, but also by the bottom (fragile) portion of the focus assembly, which is easily bent. Bending
it forward can help make certain true infinity isn’t reached too soon. Also, the tightness of the large spanner
ring holding the main assy’s together will affect where infinity focus is. Sneak up on the final tightening,
testing the focus as you tighten the main spanner ring. |
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