Nikon Series E 75-150mm Zoom Creep Repair

Repair Nikon Series E 75-150mm Zoom Creep
Disclaimer: Use at your own risk. If you ruin your lens, it’s your own responsibility.
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Getting Ready
To save time and not to leave a disassembled lens for couple of days, it’s a good idea to have the
replacement parts and any special tools ready before you start. The zoom creep problem for the
Nikon Series E 75-150mm lens comes from the material used in the zoom/focusing collar. A strip
of felt with paper backing was the only thing used for dampening between the collar and the front
half of the lens barrel. It’s in a shallow groove at the front of the zoom/focusing collar, beneath the
“Nikon series E 75-150mm f3.5 XXXXXX” engraving. This material, once failed, does not
provide any dampening for the zoom/focus collar. As shown in Fig 1, the backing of this felt strip
already turned into powder (the black dots on the surface).
Fig 1. The old felt strip
Replacement
Even one could find the original OEM replacement part; the result would still be poor. For a “better
than Nikon part” solution, a manufactured 1.8mm foam rubber (also called sponge rubber) with felt
on one side has been experimented with excellent result. Cut into the same size as the original felt
strip, it’s compressed into the groove to provide tension on the lens barrel, while the felt side,
facing the barrel, allows the collar to move smoothly. If you often deal with industrial suppliers, ask
for a sample sheet. A good alternative, which also works well, is buy foam rubber sheet and high
density felt pad (not the one used at the bottom of lamp) from crafts and hobby stores and glue
them together. The foam rubber usually comes with 3mm, 2mm, and 1mm (not common, so ask)
thickness, and they are easily available at Michael’s, Hobby Lobby and Wal-Mart’s craft
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department. It’s mostly used for scrapbook and children’s decorations, available in many colors. A
good combination is a glued 1mm foam rubber and 1mm felt pad. A 2mm foam pad ($0.33/
8”x11”) and a thin felt pad ($0.99/ 8”x11”), with combined total thickness less than 2.5mm, also
works well. Material with total thickness exceeding 2.5mm can be too strong for zoom action and
is difficult to be compressed into the shallow groove. If your foam and felt come with adhesive
back, use the adhesive backs together, but test the strength of the adhesive. To test, try to pull the
foam and felt apart. If the adhesive rips the foam or felt, it’s strong enough. Otherwise, you need
some good foam glue. Ask when you are at the craft store. There is also a thin velvet pad to
substitute the felt pad.
Tools
Seal Compressor: If you don’t know what it is, don’t worry. You can make your own. It maybe
primitive and slower, but works just fine. Prepare a steel sheet metal strip, 0.5 inch (8mm?) wide,
slightly longer than the outer perimeter of the zoom/focus collar. Although you can cut out a piece
like that from a food can (canned chili), it’s a little difficult to work with. A thicker metal strip makes
the job easier. Air duct clamp, like those used to hold vent duct to a clothes dryer, makes an
excellent compression tool. To ensure no finger is sliced and no scratches added to the lens,
smooth out all sharp edges with a deburring tool or sandpaper.
Screwdriver: Phillips 000 with large handle (not the precision clock screwdriver). If you don’t have
it, it costs just few bucks. It’s used only to tighten/remove screws.
Other tools and supplies: skewer and toothpicks (both made of bamboo); adhesive remover
(“Goo Gone”); rubbing alcohol; paper towel; small pliers; high temperature molykote grease; razor
blade or scissors; medium strength thread locker(Lock Tite blue); ruler; ring compression tool(not
required); a latex or plastic surgical glove(only the fingers needed)
Getting Started
Attach a UV filter and a rear lens cap to protect the front and the rear of the lens.
Double check infinity focus
Before you start, check the lens infinity focus on a camera. Try to focus at a distant object at 100m
(yard) and 300m away. Take a note where the distance scale is. It should be either near or at
the”∞” mark. This is the ultimate test for proper infinity focus.
Remove the rubber grip (Do not use any metal tool)
Use your fingernail and gently pull back the second row of wafers at the front edge of the collar.
Once a small gap is revealed, slide a toothpick under the rubber grip. Put a bamboo skewer, with
sharp end trimmed, under the rubber grip, and take out the toothpick. Avoid push the skewer
directly on the rubber. Roll the skewer around the collar and push slightly toward the other end to
break the thin film of adhesive under the rubber. Do so for two full rounds. Once the adhesive is
fully broken, roll the skewer again and push the rubber grip out of the groove at the back end of
the collar (lens). Make sure the whole perimeter of the grip is out of the groove, then pull the grip
towards the back of the lens and remove it. Watch out the lens’ meter coupling ridge. Do not let
the rubber grip slide out tightly against it, or it can damage the grip or the metering ridge.
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Disassembly
Once the rubber grip is removed, you’ll see a small bronze sheet metal secured with a tape.
Fig. 2 conventions used for rotation
Remove the tape and the metal piece. Clean the adhesive with adhesive remover, such as Goo
Gone. Do not put fluid directly on the collar. Clean around the long slot, but not inside. Clean the
adhesive remover (Goo Gone) with rubbing alcohol. Refer to Fig.2 for clockwise (CW) and
counterclockwise (CCW) rotational directions.
Do not remove any screws at this time! The following procedure is extremely important.
Failure to follow the alignment check will result in loss of focus!
Fig. 3 Infinity focus alignment
The guide/stop screw in the slot is marked as G. Do not remove it at this time. There are three
screws at the rear edge of the zoom/focus collar. Two are marked as A and B. Screw A is the one
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right at the”∞” mark, and is on the opposite side of the long slot on the collar. Screw B is the one
closest to the slot. These two must be identified or labeled. Pull the collar all the way towards the
aperture ring (150mm mark) and rotate CCW all the way till it stops. The”∞” mark and screw A are
now aligned with the index mark, as shown in Fig 3. Use this position of the Distance Scale mark
as an important alignment point. Keep the Distance Scale ring at this location all the time
through out the whole repair process.
Warning! Sample variation does exist. In the following process, read the
procedure carefully and always check alignment mark on your own lens.
Internally, this lens is constructed as two pieces. The front assembly (referred as focusing
assembly hereon), including 3 elements at the front of the barrel, along with the zoom/focus collar
provides focusing. The back assembly (referred as zoom assembly) is the prime and zoom lenses.
The two assemblies are linked by the helicoid.
Fig.4 End of the helicoid
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Remove three screws, including A and B. Keep the Distance Scale ring (referred as ring
from hereon) at 150mm and the”∞” mark. Pull the zoom/focus collar (referred as collar from
hereon) towards the front and separate the collar from the ring. Now you can see the
Distance Scale ring is actually not a ring, but another collar inside the zoom/focus collar.
But for convenience purpose, it will still be referred as “ring”.
Refer to Fig 4. Rotate the collar CCW until it stops. Check where the Screw hole A is
aligned on the ring. For this particular sample, it aligns with the yellow number “20” in feet
(ft) on the ring. Take a note of this. It marks the end of the internal helicoids. This alignment
is used to check proper focusing during reassembly.
Now rotate the collar along with the focus assembly CW until screw hole B is close to be
aligned with the index mark. See Fig.5. Stop at this point.
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Fig. 5 Stop here!
•
If you rotate the collar CW a little further, the internal helicoids on the focusing assembly
and the zoom lens assembly will separate. So extreme care must be used to find out what
is aligned with screw hole B at the point of the separation. Rotate the collar very slowly until
you feel the click. Stop and check what is aligned with screw hole B.
Fig. 6 Point of separation
In Fig. 6, this particular sample separates the screw marked with a solid line. Some sample
separate at the screw marked with a dashed line. Your sample can be different. Check the
alignment very carefully and take note of this. Exact point isn’t necessary. But the
alignment must be as close as possible.
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•
Pull the focusing assembly and the zoom lens assembly apart. Immediately put the
focusing assembly on clean paper on the table with the front element pointing up, and
cover the zoom assembly with a 52mm front lens cap. This way all the exposed internal
elements are protected from the dust in the environment. Move the zoom assembly to a
safe location, as most of the repair does not need this assembly.
Remove the guide/stop screw G in the slot, and pull out the front focusing assembly from
the collar. You can take a quick look at the internal of the focusing assembly now, shown in
Fig 7. Set the assembly on the table with the front element pointing up.
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Fig. 7 Focusing assembly internal
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Now it’s time to work on the replacement part. Take out the felt strip in the groove at the
front of the collar, shown in Fig.8. There is no adhesive on the back of the felt strip. Notice
there is actually 1mm gap between the ends.
Assembly
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Cut a strip of your homemade, “better than Nikon’s” dampening pad to the exact width as
the old felt strip, but slightly longer. Put the new strip into the groove, with the felt side
visible. Trim off the end and leave with a 1mm gap.
If you have the seal compressor, compress the strip all the way into the groove then push
the focusing assembly into the collar. This only takes a few seconds. If you don’t, take out
the replacement felt strip. Then put in the metal strip and expand it all the way till it’s tightly
against the inner wall of the collar. Mark the end and cut the metal strip. Smooth out sharp
edges. If a thin sheet metal is use, use a small plier to bend one end slight in the middle to
make a small notch. Install the new felt strip. Use the sheet metal strip to compress it all the
way into the groove. Expand the metal strip till the ends against each other. Use those
cutouts from a surgical glove on your index fingers to help. Another way to do it is drill a
hole on each end of the metal strip and use the ring compression tool to expand.
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Fig. 9 Not acceptable. Make sure no felt is visible.
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Make sure no felt is visible. Turn the collar upside down and push the metal strip slowly till
it’s flush with the front edge of the collar. Push in the focusing assembly slowly till it passes
the felt. Take out the metal strip from the other side of the collar. Make sure no felt is
caught in between. This process may require several try, so be patient. Align the screw
hole G with the slot on the collar, and install the screw with the spacer. Lightly tighten the
screw.
If regreasing is needed, use a toothpick to apply tiny amount of high temperature molykote
grease (or moly, available at auto stores) only into the helicoid thread of the zoom lens
assembly. See Fig.10. Wipe off excessive grease on the threads and the edge of the
threads. Grease with high volume Molykote is preferred. Use of high viscosity grease will
also help fine adjust the focusing action.
Fig. 10 Threads to be regreased
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Although precise alignment is not required, this is a good time to practice assembly. Hold
the threads of the helicoid of the two assemblies tightly against each other and slowly
rotate the focusing assembly CCW and the zoom assembly CW to engage the threads.
Once engaged rotate back and forth several times at the full range of the helicoid to
squeeze out excessive grease and then disassemble. Clean off excessive grease.
Carefully align the screw hole B with the mark during disassembly phase and engaged the
threads. To check for proper installation, rotate the focusing assembly CCW all the way till
it stops. Pull the collar towards the distance scale ring and check screw hole A for
alignment. Fig. 10 shows this particular sample was installed properly.
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Fig. A check alignment
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Now turn the collar CW slightly until screw hole A is aligned with infinity mark. Push the ring
into the collar and align the holes. Install three screws and lightly tighten. For a final check of
infinity focusing. Attach the lens to a camera and test it on the distant objects as you did
before you started.
If infinity focusing is satisfactory, remove the screws, including guide/stop screw G in the long
slot, one at a time. Apply medium strength thread locker (Lock Tite blue) to the threads and
reinstall. Fully tighten all screws this time. DO NO OVERTIGHTEN.
Cover the long slot with the original bronze metal and secure it with scotch tape. Reinstall the
rubber grip from the back side of the lens.
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