\ General Repair Tips
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\ General Repair Tips
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©Infotech 2004
Several tips and procedures apply to a variety of cameras—modern or antiques. We've assembled several of these procedures in this article. If you're new to camera repair, the information provided here should help you get started.
DISASSEMBLY TIPS
1. Keep parts in order as you remove them. Reassembly is the reverse of
disassembly. If you know the sequence you used to remove the parts, you’ll also
know the sequence to replace the parts. In some cases, keeping the parts in
sequence may require more bench space than you have. You may then prefer to use
parts boxes like the one below right—or even egg cartons—to hold the parts.
2. Keep springs, screws, and washers with the parts they hold or operate.
Screws are often specialists—they go in a specific position or with a specific
part. Using the wrong screw may damage screw threads or cause other problems.
The parts boxes, like the one shown at the right, can again be helpful if space presents a problem.
The individual compartments help you keep the screws and washers with the proper
parts. Plus you can group related parts together—for
example, all the screws that hold the front plate in one compartment, all the
screws that hold the bottom cover in another compartment, etc.
3. Before you remove a part, try to figure out the purpose
of that part and how the part works. This knowledge will be invaluable for
reassembly. It’s difficult to test the operation of the part if you don’t know
what the part is supposed to do.
4. Make notes and sketches of such things as spring positions and washer
positions. A digital camera can be very useful to provide a picture
reference. Record the step-by-step disassembly.
5. When you remove a spring, it’s usually best to disconnect the longer end
first. Keep one finger on top of the spring—just in case the spring decides
to fly into space. On reassembly, normally connect the short end of the spring first.
6. Use scribe lines to mark the positions of internal parts (but never on
external parts where you can see the scribe lines after reassembly). For
example, perhaps you’re removing a mechanism plate. On reassembly, the mechanism
plate must go right-side up and in the correct rotational position. Put one
scribe line on the mechanism plate and a matching scribe line on
the shutter
housing. The scribe line on the mechanism plate tells you which side goes up.
For the proper rotational position, just match your two scribe lines. And
scribe the timing between gears before you disengage those gears. The timing
may or may not be critical. But scribe the timing anyway, just to be safe. Place
a scribe line on the tooth of one gear and another scribe line on the tooth slot
of the second gear.
In the illustration at the left, we've used a watch scriber to scribe
the position of the blade-operating ring with respect to the shutter housing. A
scriber has a sharp, carbide tip that will scratch a line in most metals; in
watches, it's used to mark a repair number inside the case back.
However, you don't need a scriber for the soft metals used in shutters. Just
about any metal tool with a sharp tip will work.
7. If you’re working from a manual or other source of information, be on
guard for variations. Use the manual for assistance—but don’t rely on it
entirely. Manufacturers often make modifications. There may very well be minor
variations between the mechanism on which you’re working and the one that’s
described in the manual. Even worse, not all manuals are perfect—there may be a
mistake or two, even in manufacturer’s manuals.
8. Study the mechanism during disassembly. Try to get an idea as to how
the unit works—that information can help you on reassembly, particularly in
testing and troubleshooting.
9. On reassembly, check the operation of each part after you install it.
Make sure that moving parts move freely and that the part does what it’s
supposed to do. If you remember to check each part after you install it, you
know the mechanism will work properly when you complete the assembly. But if you
don’t check each part—and if the mechanism then doesn’t work after
reassembly—you may have difficulty locating the problem.
10. Screws should be tight enough that they don't work loose. But with brass screws, plastic screws, or screws with very small threads, there's some danger of breaking the screw. With antiques, that can be a problem—you may not be able to find a replacement screw. One method you can use is to first firmly tighten the screw; then keep your screwdriver in place and hold the screw in the tightened position for a second or two. Holding the screw in the tightened position allows the screw to seat. Vibrations—for example, from an airplane ride—cause screws to work loose. With a modern camera that you're using, you want the screws very tight. But with an antique that's just going to sit on a shelf, the screws aren't as likely to work loose.
What do you do if you break a screw? Usually the main problem is in removing the threaded shaft of the screw from the mechanism plate, camera body, or other part into which the screw fits. If there's a portion of the screw thread extending above the part, you may be able to cut a screw slot—use a screw-slotting file to cut a screw slot in the broken end of the screw thread. You can then use a screwdriver to remove the threaded shaft. But quite often the screw thread is flush with the part.
First try "tickling" out the screw thread. Push your closed tweezers against the outer circumference of the screw thread and push the screw thread in a counterclockwise direction (clockwise for a left-hand thread). Continue trying to push the screw thread in the unscrewing direction a little at a time. When there's a sufficient portion of the screw thread extending from the part, you can grab the screw thread with your needle-nose pliers. Then continue turning the screw thread until you can remove it from the part.
If the screw thread is too tight, the tickling technique won't work. You may then have to drill out the screw thread. But that's dangerous—the screw thread may be harder than the mechanism plate, camera body, or other part. Often the screw is steel and it goes into a brass part. Most drill bits cut in the screw-tightening direction. So, as you attempt to drill out the thread, you're actually tightening the screw. Fortunately, you can get special drill bits that cut in the opposite direction—the direction that loosens the screw. When you turn the drill in the loosening direction, you'll often find that the drill bit grabs the screw thread. The drill then unscrews the thread rather than actually drilling it out. You can get the special drill bits from Fargo Enterprises (left-hand drill bits).
Here's another concern you'll sometimes encounter
regarding screws—locating (or shoulder) screws. A locating screw has a shoulder—a
section without screw threads—that passes into a hole in the part held by that
screw. The shoulder serves to precisely position the part being held—perhaps a
mechanism plate where the position is critical. Some of the screws holding
the
part may be locating screws while others are regular screws. If you know in
advance which screws are locating screws, remove those screws last. Why?
Tightening the other screws tends to shift the part against the shoulders of the
locating screws. The locating screws may then be very tight; they'll be easier
to remove after you take out the other screws. But replace the locating
screws first. The locating screws then serve their purpose to properly
position the part.
OTHER THREADED PARTS
1. Threaded parts—such as retaining rings and lens barrels—may not want to start
properly. Be very careful to avoid cross-threading the parts—the finer
the screw threads, the more easily you can cross-thread the parts. Here’s one
reassembly tip that usually works: start by turning the threaded part in the
opposite direction (the direction for unscrewing the part) while applying slight downward pressure. For example, suppose
you need to turn a part in a clockwise direction to screw it onto another part.
Start by turning the part in a counterclockwise direction. When you hear (or
feel) a slight “click,” you’ve found the starting thread. Now turn the threaded
part in the proper direction (clockwise in our example).
2. Most threaded parts have right-hand threads—you turn the screw, retaining
ring, etc. in a counterclockwise direction to remove it and in a clockwise
direction to install in. But be on the lookout for left-hand threads. If
a part won’t unscrew by turning it counterclockwise, you may have to turn it
clockwise for removal. Left-hand threads may be used in cases where the normal
operation of the part may cause it to unscrew. For example, you turn the wind
lever in a counterclockwise direction to cock the shutter—that’s the direction
that may unscrew a right-hand thread. It’s therefore not unusual to use
left-hand threads around the wind mechanism, such as the cap screw that holds
the wind lever. Try to avoid using excessive pressure when removing a threaded
part—if you’re turning the part in the wrong direction, you may break a screw or
strip screw threads. With antiques—and even with modern cameras that are a few
years old—you can’t always get replacement parts.
3. If a ring has two slots or two holes spaced 180°apart, it's most likely a threaded retaining ring. Here you should have a spanner wrench like the one pictured at the right. Spanner wrenches come with straight tips for slots and pointed tips for holes; the spanner wrench shown at the right accepts interchangeable tips.
For example, in folding cameras a
retaining ring usually holds the shutter to the lens standard. You can
reach the retain
ing
ring by collapsing the bellows (storage position) and opening the camera back as
in the photo at the left. In this example, use a spanner wrench with straight
tips to unscrew the retaining ring. The illustration below of the front of the
Miranda shows a situation where you want the pointed tips—unscrewing the
retaining screw that holds the self-timer cocking lever.
It's sometimes difficult to reach a retaining ring that holds a shutter—there's not much room when you're working through the back of the focal-plane aperture. However, you can reposition the tips in the versatile spanner shown above; this flexibility allows you to reach and unscrew most retaining rings. In illustration A below right, we've flipped the tips 180° from the illustration above; a spring-loaded ball locks the tips in place. Or you can tilt the tips as shown in illustration B below—change the angle to reach the particular retaining ring within the limited space for the spanner. Careful: Since the tips in B are no longer locked firmly in place, be very careful to avoid slipping. If you slip, the spanner-wrench tip could scratch the retaining ring or, worse yet, the rear lens element.
4. To unscrew a
retaining ring or other part that doesn't have notches for a spanner wrench, you
can use a piece of rubber to provide a grip. Or you can use rubber stoppers that
come in a variety of sizes. Another handy to
ol is shown below right—a tool designed for unscrewing the backs of watch cases. The tool has
a bottle stopper on one end to provide a suction grip; a chair tip at the other
end serves as a handle as well as a rubber grip for other sizes. A hole in the
tool allows you to insert a rod for increased torque. You can get the tool from
Fargo Enterprises as well as from companies that sell watch-repair supplies.
5. If a threaded part is frozen in place by corrosion, rust, or a locking agent, you may be able to get the threads loose by using a solvent such as acetone (but never use acetone on plastic parts—stick with alcohol). Apply the solvent just to the threads or between the threads of one part and the threads of the other part. Allow the solvent to penetrate and then try to loosen the parts. You may have to reapply the solvent several times.
Here's another technique that sometimes works:
lightly tap the retaining rings or barrel using a brass or fiber hammer. Tapping
the frozen part with a hammer will often break loose whatever is locking the
threads. But don’t tap so hard that you mar the part—especially if that part can
be seen from outside the mechanism. You may want to protect the part with a
rubber pad; then tap the rubber rather than the part.
As a last resort, you can use penetrating oil such as Liquid Wrench™,
available from hardware stores.
Work a small amount of the penetrating oil into the junction between the threads
of one part and the threads of the other part. But, unless you’re going to
completely disassemble the mechanism, be very careful to avoid getting the
penetrating oil into other parts of the shutter. As the name states, penetrating
oil does penetrate. If the oil gets on the shutter blades, it will freeze the
operation. You may then have to do a complete disassembly to clean the parts. Be sure to thoroughly clean any parts on which you’ve used the
penetrating oil.
BLADE-TYPE SHUTTERS
1. Disassembly of a blade-type shutter often requires unscrewing the front and
back lens cells. You'll sometimes find that a lens element is loose after you
unscrew a retaining ring—that is, not contained
within a cell. Here it's critical that you replace the lens element right side
up. You can tell if a lens element is upside down when you check the focus—the
lens doesn't focus at infinity. But to facilitate reassembly, you can mark the
lens element. Use a soft pencil to draw an arrow (>) on the edge of the lens—the
arrow points to the front of the shutter.
2. Avoid touching the shutter blades and diaphragm leaves with your fingers—always use tweezers. The oil from your fingers will quickly etch its way into the metal, leaving permanent marks. If you do accidentally touch a shutter blade or diaphragm leaf, clean the part immediately (see the article, Cleaning Techniques).
3. Removing the mechanism plate of the shutter frees the shutter blades. Before
you remove the mechanism plate, move the blade-operating ring (the ring that
carries the shutter blades) to the blades-opened position. The blades then
have a better chance of staying in place when you remove the mechanism plate. If
the blades stay in place, you have an opportunity to note the proper starting
position and direction of installation as described in (3) below.
4. After you remove the mechanism plate, note the positions of the shutter
blades—the position of the starting blade and the rotation for assembly
(clockwise or counterclockwise). Also note any special blades—blades that are
different in shape from the others. The special blades, used in many shutters,
must go in specific positions (usually—but not always—the first blade and/or
the last blade). Once again those reference pictures from a digital camera (or a
film camera if you can wait for the processing) can be invaluable.
5. Also note the position of the blade-operating ring (the ring that
carries the shutter blades). You might use scribe lines to mark the
blade-operating ring in the blades-opened position (see shutter photo near the top of this
page).
6. You should probably avoid disassembling iris diaphragms. Unless you’re
blessed with excellent dexterity, the diaphragm leaves can be difficult—and
frustrating—to reassemble.
CAMERAS
1. With an unfamiliar camera, you should normally remove the bottom cover
first (if the bottom cover is a separate part). In most cases, you won’t
cause damage or lose timing points by removing the bottom cover. Plus, with the
bottom cover removed, you can often gain valuable information about the
camera—both as to the operation and to the condition—just by observing the
parts.
2. Removing the top cover may disturb critical timing points, especially
in a camera that uses a cross-coupled exposure meter. Here a repair manual may
be invaluable—use the timing information someone else has already discovered. It
usually helps to make a note of your disassembly settings (shutter speed, film
speed, etc.). Check the manual to see what settings you should use for
disassembly. Using the wrong settings may even cause damage. The exposure
meter or other parts may be under spring tension. On disassembly, use the settings that let off as much of that spring tension as possible. In
some cameras, the spring tension on the exposure meter housing may cause the
meter to rotate so fast that the exposure-meter needle breaks. Or, in the Canon
AE-1, a thin tungsten wire connects the speed-knob parts to a spring-loaded
resistor. Using the wrong disassembly settings may cause the spring-loaded
resistor to break the tungsten wire. Usually the speed-knob settings that let
off most of the spring tension are bulb
and the fastest film speed (that’s also true for the AE-1). But there are
exceptions.
3. You’ll usually have to remove the rewind knob to pull the top cover. In most
cases, the rewind knob simply screws onto the
top of the rewind shaft. Wedge the
rewind fork to prevent it from turning (you can just slip the handle end of your
tweezers through the rewind fork as shown at the right). Then unscrew the rewind
knob. However, use caution—look for a screw at the top of the rewind knob. The
screw may be holding the rapid rewind crank to the rewind knob. Or it might be
holding the rewind knob to the rewind shaft. In the latter case, the rewind knob doesn't screw onto the rewind shaft.
Remove the screw if it’s holding the rewind knob to the rewind shaft. Then lift
off the rewind knob.
With the Nikon F shown at the right, there's another caution. The rewind knob does screw onto the rewind shaft as with most cameras. However, a setscrew locks the rewind knob. Loosen the setscrew before you attempt to unscrew the rewind knob. A locking setscrew is unusual. But it serves a good purpose. People often try to turn the rewind knob in the wrong direction when they're rewinding the film. The rewind knob then unscrews, leaving the photographer with loose parts. The loose parts under the rewind knob may include a spring (usually a flat spring) for the rapid rewind crank and one or more washers. Nikons often have several loose parts under the rewind knob. Unscrew the rewind knob carefully and note the positions of any loose parts.
Note: If the rewind knob is very tight, it's safer to
grip the rewind knob (rather than the rapid rewind crank as we're doing in the
illustration above—just to prevent damage to
the rapid rewind crank).
4. It’s often necessary to remove or peel back leather-like body covering to
reach retaining screws. In some older cameras, like the early Rolleiflex
cameras, the body covering is genuine leather. Later cameras—including
later Rolleiflex cameras—use a plastic material that
looks like leather (usually termed "leatherette"). Removing the body covering
without damage may present a problem—especially in an old camera. The body covering suffers with age. Rather than peeling off, the
body covering breaks or tears. You can obtain
bulk leatherette to make new body covering. But unless that material
closely matches the original, you’ve lowered the antique value by changing the
appearance. If you’re working on a newer camera—one for which you can get
replacement parts—you don’t have to worry about preserving the old body
covering. Just order replacement body covering from the manufacturer (but you
may want to make sure you can get the replacement body covering before you
completely destroy the old body covering).
If you really have to remove that body covering, use a flat tool such as a jeweler’s screwdriver to get a starting point—pull a corner away from the camera body. You can then use denatured alcohol or isopropyl alcohol as a solvent (don’t use acetone—acetone may destroy the body covering). Apply the alcohol between the back of the body covering and the camera body. Then carefully lift up another section—the section loosened by the alcohol. And reapply the alcohol to the next area that doesn’t want to come loose. When you replace the body covering, use a rubber cement such as Pliobond™. You should then be able to remove the body covering if necessary. Some technicians prefer using a special double-stick tape to hold the body covering; you can get the double-stick tape from Fargo Enterprises or other tool suppliers.
5. With cameras that accept interchangeable lenses, the
flange-focal distance (the distance between the lens-mounting ring and the film
plane) is critical. If you remove the front standard (also called the front
plate or the front apron), watch for spacer washers at the screw po
sitions.
The washers fit between the front standard and the camera body. Be sure to
return the washers to the same positions. Removing the lens-mounting ring
carries the same precaution—there may be washers under the lens-mounting ring at
the screw positions. That's true in the Tower camera (similar in design to the
screw-mount Leica) shown at the left.
6. Be on the lookout for mechanical adjustments. Try to scribe the
positions before you disturb the adjustments. For example, there may be a screw
passing through an elongated slot. The slot seems much longer that necessary.
But this is an adjustment point. After loosening the screw, you can move it to a
different position along the slot. In this case, you can put a scribe line at the side of
the slot that marks the screw position. Pentax often locks adjustments with red
lacquer. The color serves as a warning—this is an adjustment point.
COSMETICS
It's often possible to improve the appearance and value of the camera
without disassembly. Here are a few cosmetic repairs.
1. Clean the covers and the lenses. Some technicians
like to use Windex™ for cleaning the exteriors of cameras—the
leather body covering as well as the covers.
The ammonia in Windex™ gives the camera a new-camera aroma. Windex™ makes a good
general-purpose cleaner, both for the covers and for the optics. A chamois is
handy for wiping off the camera exterior (but don't get any solution on the
chamois). You can get a chamois from a hardware store.
2. Use leather dressing to improve the appearance of the body covering (if the body covering is leather or leatherette). Fargo Enterprises has leather dressing for use on camera leather. To recolor the body covering, you can use liquid black shoe polish such as Kiwi™.
3. Quite often you'll find that the engraved calibrations in speed knobs and other controls have lost their color. What was once a black or red calibration may now be just the color of the metal. You can use lacquer sticks to fill in the calibrations. The lacquer sticks come in different colors. Just rub the lacquer stick over the engraved calibrations. Then rub the surface of the part with a Kimwipe™ or cloth to wipe off the excess lacquer, leaving just the lacquer that fills the calibrations.
You can even use the black lacquer stick for small leatherette repairs—use the lacquer stick to fill in small areas where the leatherette has broken off. Then dimple to lacquer with your tweezers or screwdriver to simulate the leatherette pattern.
4. SLR's often use a light-trapping felt material inside the
mirror box. The material seems to catch and hold tiny bits of dust or lint that
are visible with the lens removed. You can easily remove the dust and lint with masking tape. Just
touch the sticky side of the masking tape to the mirror-box wall.
5. Brass and aluminum parts often suffer from corrosion, giving a dingy appearance to the metal. The aluminum counter dial shown at the left provides a good example of how corrosion can detract from the appearance. You can polish brass parts with Brasso™, a polish that's available from convenience and hardware stores. Use an aluminum polish for aluminum and other metals. Jewelers' rouge, a very fine polish that's available from watch-repair suppliers, makes a good finishing polish. Apply the polish by hand or with a felt wheel in a rotary tool such as a Dremel™ tool. The counter-dial picture at the right shows the results of polishing. Be careful in polishing that you don't change the appearance from the original; changing the appearance can lower the antique value. If the surface has a design—such as etched or embossed patterns—avoid using an abrasive polish. And don't use power tools. You may polish off the design, a major blow to the antique value. The counter dial shown above should be hand-polished to prevent removing the recessed numbers. Refill the calibrations with a black lacquer stick (#3 above).
6. With age and exposure to the elements, the porous-plastic
light traps and cushions (also called foam or sponges) tend to
deteriorate.
Sometimes the deterioration is so bad that you'll find the sticky black residue on the focusing screens and mirrors of SLR's—this
comes from the porous-plastic strip at the top, front of the mirror box shown at
the right. Here the
porous-plastic strip serves as a cushion—when
the mirror moves up, it strikes the strip of porous plastic. When the
porous-plastic strip is completely deteriorated, the mirror makes a bone-jarring clunk
as it reaches the picture-taking position. You can get the porous-plastic
material in bulk sizes. Just cut the bulk material to the size you need. A
rotary cutter makes a good tool for cutting the porous-plastic material. Some of
the porous-plastic material comes with a self-adhesive backing; just peel off a
piece of protective paper and cement the porous-plastic strip in position. If
the porous plastic doesn't have the self-adhesive backing, use Pliobond™ or a similar
rubber cement to cement the
new material in position. You'll also find porous-plastic light traps at the back of the
camera and the inside of the back cover. These light traps are prime suspects if
there's a light-leak problem. And how about cleaning off the gunk that's the
residue from the porous plastic? Use the standard materials and procedures
described in our tutorial on cleaning optics.