In the late 1960s, my college roomate asked me to fix the lens on his Mamiya
35mm camera. (I don't know what got into him.) The problem was that the iris
blades didn't stop down fast enough to get to the correct setting in time,
causing random but gross overexposures.
The solution was to disassemble the lens, clean out the pivot holes through
which the little pins staked to the iris blades passed, and reassemble the
lens. Cleaning was accomplished with the very tip of a round swiss file,
making the pivot hole slightly larger, so brass wear dust would simply fall out
of the space between the steel pivot pin and pivot hole (in brass), rather than
accumulate and cause the pivot to become stiff. This was basically a minor
design flaw - the tolerances were too tight for an unlubricated bearing, and
the bearing had to be dry or it would draw dirt.
The problem was that to get to the iris blades, one had to disassemble the main
focus bearing, which consisted of two v-shaped races in the edges of two brass
rings, filled with one or two hundred 1mm steel balls, lightly lubricated but
not really greased, so they don't much stick to the races.
So, roomate is watching intently as I take the lens apart and gently shake all
those little balls out into a seamless aluminium baking pan. Shaking? This
really isn't looking good. Eventually he gets the courage to ask just how do I
plan to get all those tiny balls back into the lens. I parry the question,
finish reaming out the pivot holes. He still worries, mostly in silence.
Tweezers don't work well on such things, and most of the balls will likely be
lost. How can this work....
The trick is to lay the lens out with bottom race horizontal, pick up a chain
of balls with a small screwdriver and a magnet touching the screwdriver blade,
lay the chain down in the race, then pull the magnet away from the screwdriver
blade, releasing the chain in place. It took two or three repeats to get all
the balls back in place. Then gently screw the rest of the lens back together,
being careful not to dislodge the tiny little balls.
Afterwards, the lens worked just fine, and was used for decades.
So, camera repair and medicine have something in common: it's best if the
patient's loved ones don't watch.
Joe
At 3:04 PM -0400 10/15/02, John Hermanson wrote:
>There are 370 of those ball bearings (2 races of 185 ea.) , golly, good
>luck.
>_________________________________
>John Hermanson www.zuiko.com
>Camtech, Olympus Sales & Service since 1977
>21 South Lane, Huntington NY 11743-4714
>631-424-2121 For Free Olympus manuals,
>please call 1-800-221-3000
>_________________________________
>----- Original Message -----
>From: "Jim Brokaw" <jbrokaw@xxxxxxxxxxx>
>To: <olympus@xxxxxxxxxxxxxxx>
>Sent: Tuesday, October 15, 2002 12:27 PM
>Subject: Re: [OM] setting infinity focus on Zuiko 35-70/3.6 lens
>
>
> > Only about 30 of them fell out, and I managed to find about 25 and put them
> > back... then screwed the end on 'vewwry wewwry carefullwy'. That was one of
> > those "oops...!" moments... It all still works the same, just won't focus
> > correctly.
> > --
> >
> > Jim Brokaw
> > OM-1's, -2's, -4's, (no -3's yet) and no OM-oney...
> >
> >
> > on 10/15/02 7:16 AM, John Hermanson at omtech@xxxxxxxxx wrote:
> >
> > > Are you serious about the ball bearings spilling out? I hope you were
> > > kidding.
> > > _________________________________
> > > John Hermanson www.zuiko.com
> > > Camtech, Olympus Sales & Service since 1977
> > > 21 South Lane, Huntington NY 11743-4714
> > > 631-424-2121 For Free Olympus manuals,
> > > please call 1-800-221-3000
> > > _________________________________
> > > ----- Original Message -----
> > > From: "Jim Brokaw" <jbrokaw@xxxxxxxxxxx>
> > > To: "Olympus mailing list" <olympus@xxxxxxxxxxxxxxx>
> > > Sent: Monday, October 14, 2002 11:34 PM
> > > Subject: [OM] setting infinity focus on Zuiko 35-70/3.6 lens
> > >
> > >
> > >> I have a nice 35-70/3.6 zoom that won't focus to infinity. When the focus
> > >> ring hits the infinity stop it is somewhere about 12-15 feet, not
> > >> infinity.
> > >> I already unscrewed the end and spilled all the little 1mm ball
> > >> bearings...
> > >> I got most of them back (I think).
> > >>
> > >> I didn't see anything obvious under the focus ring, so what is the
> > >> secret?
> > >> Any advice or help is appreciated.
> > >>
> > >> Thanks,
> > >>
> > >> Jim Brokaw
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