Today I got my garage sale special 50/1.8, courtesy of Doris (thanks Doris! :-)
Glass looked really good, but the aperture ring was frozen and it appeared to
have some serious corrosion on the rear mount.
Well, after about 3 hours of cleaning, dissecting, cleaning, and more
cleaning, it now works smoothly, and even looks pretty good!
I removed the rear lens mount flange first, and found more corrosion inside,
although the glass and focussing helicoid looked fine. I had to use emery
paper to remove the corrosion on the brass flange, which left some pitting in
a few places.
Then, removing the front ring with "MC ZUIKO etc" using a small screwdriver
tip, I found the cause of the corrision: salt crystals were found beneath the
ring. Removing the front element group held by 3 screws also revealed more
salt and dampness, and the cause for the frozen aperture ring: the steel
coupler had tons of rust jammed between it and the aluminum barrel,
combined with grains of salt jammed between the ring and barrel.
(Watch out for the tiny ball bearing for the aperture "click", although it is
usually stuck with grease)
After seeing all this salt I decided to thoroughly rinse and scrub all parts
(aside from the elements) to remove the salt. Some more emory paper on
the corroded parts, plenty of q-tips to clean the focus helicoid, and some
stiff
dampened paper to clean the aperture ring groove, and all was ready to
reassemble.
It went back together without a hitch after a few false starts lining up the
aperture coupling levers (I soon found they are designed to fit only one way,
with slots mathing the different sized levers).
After all this, I am amazing how much work one can do on this lens with
simple tools and without fear of dissassembling elements. I'm not sure what
is involved in separating the helicoid, but I may try this next - there is
still a
tiny amount of grit which can be felt.
Shawn & Janis Wright
swright@xxxxxxxxx
http://Zuiko.sls.bc.ca/~swright
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