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  1. #1

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    Nikon F4 aperture lever repair

    WARNING : Those instructions are for skilled persons with some knowledge of mechanics and electronics. Don't follow if you are unsure about your skills.

    F4 Aperture lever problem driving the lens down.

    This will be a long thread with ~100 pictures. please be patient, i don't have enough time to edit all in one day so return after few days. PLEASE KEEP THIS THREAD CLEAN. Post your questions & comments here : http://www.apug.org/forums/forum52/1...pletely-3.html
    Tools needed : slot screwdriver 1 mm width, screwdriver PH 00, soldering iron, cutter / knife, sealing plastic bags & labels.
    Put all disassembled parts and most important the screws in sealing plastic bags and write with a marker from where they were removed, also you can take pictures for reference.

    Disassembling instructions:
    Left side

    1: remove rewind knob
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    2: remove clip ring, washer, lever. Pay attention to lever spring and small pin
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    3: remove the round nut retaining iso selector, 3.1 remove iso selector. Pay much attention to brush from behind
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    4: remove 3 screws of left cover. 4.1: Press lever R2 to rewind position. 4.2: Remove left cover.
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    Last edited by F4user; 06-05-2014 at 05:42 PM. Click to view previous post history. Reason: title change

  2. #2

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    Episode 2 - right side cover

    Right side
    5: Remove ornament cap of exposure compensation knob
    5.1: Remove the screw & knob
    5.2: Remove 3 screws of indexing plate.
    5.3: Remove mode selector.

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    6: Remove shutter speed selector rubber. Attention do not scratch paint of knob. Insert slot screwdriver at the bottom of knob and use a round tooth stick to remove the rubber
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    7: Remove 3 screws placed at 120 degrees around. Use 1mm slot screwdriver. Do not loose too much, one turn at a time each until the knob is free. Pay attention the screws are very small. Do not loose the spring inside.
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    8: Using two 1mm slot screwdrivers remove clip ring 8.1: Remove illuminator lever
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    9: Remove red dot and the screw.
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    9.1 Remove right side cover screws and right cover
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    Mandatory - see the next post. Forum's limit is 15 pictures per post.
    Last edited by F4user; 06-05-2014 at 04:38 PM. Click to view previous post history.

  3. #3

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    Attention to this pin. Do not loose.
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  4. #4

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    Episode 3 - more work

    Bottom cover

    10: Peel bottom rubber. The rubber is attached using double adhesive tape. Start from battery side, start gently. Insert a small slot screwdriver between the rubber and brass sheet. Between rubber and the bottom case there is a brass sheet also attached with adhesive tape. Pay attention and do not peel the brass sheet, you will have more work to do. Press the brass down with a slot screwdriver. Plastic knife can be used.
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    11: Remove bottom cover screws
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    12: Remove bottom cover. Start from battery side. Lift gently and with care. There is adhesive between brass sheet and tripod nut and allow time to peel off. Pay attention to the wires. Do not insert any tool between bottom cover and the rest of the case, most of the electronics are there.
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    13: Using soldering iron remove the connections. Pay attention to static electricity. Do not wear plastic fabrics, use only cotton and do not wear plastic shoes. For ex: touch metal case of a running PC to discharge static electricity. Avoid excessive movement on the chair where you stay to avoid recharge with static electricity. From this step forward this precautions apply to all steps because the electronics will be exposed.
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    14: Remove tripod socket plate. Pay attention: the screws have thread blocking paste. Apply increasing force until they start to move.
    14.1 Remove more connections ( 2 black & 1 orange wires on left side and all on the center ). Peel black acetate tape up to the dotted line only. Remove flexible band connector with small movements ( green markings ) keep parallel to the socket. Pay attention to flex cable.
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    Top .. less.

    15: Remove shutter button assembly screws. Keep them close for reassembly. Remove LED connections ( green and orange ) .
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    15.1 : Gently lift shutter release button assembly ( screws side ). Pay attention to the flex cable on the front. Lift as much is need to insert a screwdriver to remove battery plate screws. Reattach shutter button assembly using the screws
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    Last edited by F4user; 06-06-2014 at 01:58 PM. Click to view previous post history.

  5. #5

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    Episode 4 - Big split

    I recommend the back film cover to be in place to protect shutter blades.

    16: remove right side and left side rubbers
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    17: Remove right & left side rails and the screw near right side rail. The right side rail have some light seal sponge over it. Cut it clean after screws removal.
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    18: remove cover and pressure plate over flex cable contacts
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    19: Remove front screws. Don't touch the screw with yellow marking. Remove all ( 7 ) electrical connections near focus mode selector
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    20: Remove side screws ( left & right ) and back
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    21: Remove LCD - LED assembly screws. Gently lift the assembly starting from grip side no more than 3-4 mm. Pay attention to the flex cable on the ISO side, the flex cable is short . Lift the assembly until is free from its position.
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    Take a break. You need it

    22: Now you can start split the camera. Pay attention to the flex cables on battery side. Keep them inside the case with fingers or a small plastic tab. When the cases start to split swap over the case the flex cable of LCD-LED assembly. Pay attention don't break it.
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    Gently move the front case up, down left & right until complete split. Now you can admire Japanese technology.
    Click image for larger version. 

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  6. #6

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    Episode 5 - Who killed JR Ewing

    Inside job.
    As you can see the mirror mechanism and aperture lever are pure mechanical with no motor.
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    The mechanism from back side of the F4's body push 2 levers toward front of the body , one for charge ( green ) and another for shoot ( blue ) releasing mirror mechanism and aperture lever mechanism, both are spring actuated. Pushing the lever ( green arrow ) will charge the mechanism. Push release lever ( blue arrow) for shoot mode. The aperture mechanism must follow the mirror mechanism and is more complicated having a lot of toothed gears.

    Click image for larger version. 

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    The culprits for defective work are: aperture lever spring and hardened shaft grease of toothed gears.
    The aperture spring is under PC board and is hard to take a photo of it. Will come.

    Charged position look like this:

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    Observe mirror lever ( pink arrow ) secondary mirror ( purple circle ) and aperture mechanism ( yellow circle )

    Release position:

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    Observe mirror lever ( pink arrow ) and aperture mechanism ( pink circle ).
    The lever is in touch with the aperture lever adjusting screw.
    When all mechanics are in released position you can play ( move ) the aperture lever with your finger to see if the movement is fast. Also you can charge - discharge mechanism to see if the aperture driving mechanism is fast enough to follow mirror mechanism. Pieces shown as in the picture above must move together or very close. Total time must be under 20 ms and that's fast, hard to see.

    Faulty position because stuck gears:

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    Observe " mirror up " position ( green ) and aperture mechanism in charge position behind adjusting screw.

    The repairs.

    First remove the circle clip of the first gear and remove the first gear.
    Pay attention to the rest of gears, they start to spin up fast.

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    Remove screw of the plate. Be careful there is a spring under brass gear and can escape in the room.

    Click image for larger version. 

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    Clean the remaining gears shaft pouring some cleaning fluid. Also clean riveted mechanism
    I use for everything, even for lens, MOTOREX brake cleaner. http://www.motorex.com/index.cfm?oid...=eintragDetail
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    Repeat until gears and levers move easy. Oil with clock oil a very very small quantity
    I think is not necessary to say removed gears need also cleaning.

    Aperture mechanism:

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    The aperture spring soften with time so there are 2 possibilities : change or adjust the mechanics. ( next episode )
    Last edited by F4user; 06-18-2014 at 03:41 PM. Click to view previous post history.

  7. #7
    frank's Avatar
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    Wow, thanks for posting this. I paid $100 to have this repair done on my F4. Money well spent in my case.

    This damage was caused to my camera by using a lens with a sticky aperture.
    My blog / photo website: http://frankfoto.jimdo.com/

  8. #8

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    Excellent article. Very well done. Larry Lyells would be proud. BTW, I am a camera technician.



 

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