Problem with Nikon FG AI follower

Discussion in 'Modern Film Cameras' started by craigd, Jul 3, 2011.

  1. Yesterday I was given a Nikon FG, a pleasant little SLR from the early '80s with program, aperture priority, and manual modes. It seemed okay electrically and mechanically at first glance, but I've noticed a minor problem that I hope someone can tell me how to fix. The AI follower on the camera body doesn't move very far. If I turn the lens down to f/22 and then open it up, the follower stops at about f/11 or f/8. I can push it farther by hand, but it won't go farther by itself. The net effect of this is that the camera is usable in program mode (where the lens is always left at its smallest aperture) but not in the other modes where you would actually turn the aperture ring. Well, it wouldn't work below about f/8, at least.
    I've tried exercising the follower by hand (I once fixed a Minolta XK this way), but it doesn't seem to be doing any good. Does anyone have any other suggestions about what to do to fix it?
  2. It's possible that the inner ring of the AI mechanism is gummed up with dirt preventing it from moving freely. The AI follower on the FG is a 2 pc. plastic ring. The external plastic ring with the follower tab keys into another plastic ring that fits flush inside a hole behind the mount flange. If there is dirt on the outer diameter of the second ring, it could cause enough drag to prevent the mechanism returning to the max aperture position.
    If you remove the mount flange from the FG (don't worry, no springs will go flying, but do note the orientation of the flat spring/shim immediately behind the mount) you can lift the AI follower tab ring straight off and you will see the second ring that connects to the indexing mechanism inside the camera. Try applying a little solvent around the outer diameter of the ring and see if that frees things up.
    If that doesn't help, then the problem is probably internal.
  3. I have succesfully fixed this problem by spraying WD-40 into the ring. Should be careful. Many people seriously said it's bad but I have done it and it works. Just excercise care.
  4. I would try a little bit of Ronsonol or similar lighter fluid, before WD-40, which can leave a sticky residue.
  5. Well, I didn't really want to take the lens mount off unless I had to, and I didn't have any lighter fluid on hand, but I did have some WD-40. Here is what I did: I removed the lens from the camera, but did not unscrew the lens mount. I folded up a piece of tissue and held it tightly over the lens mount, exposing only the outer edge where the AI follower ring is. I applied three very short bursts of WD-40 more or less equally spaced around the lens mount and immediately wiped away excess. Then I threw away the tissue, held the camera face down (in the hope of allowing dirt particles to fall away) and exercised the AI follower with my finger, sliding it around the lens mount as far as it would go (toward the f/32 position), then back again. After a few minutes of this, it moved much more freely. It now easily follows a lens all the way to f/1.8. Unless it gets sticky again, I think I can consider this a reasonable solution. Thanks to all for their suggestions.
  6. Among camera repair persons, WD40, and its fellow travellers ,is known as the Camera Killer.
    Many will not touch a repair which smells of this product. The common wisdom is that it may have a place if allowed to settle in a container. The lighter,top fraction can then be used for light lubing.
    It is not hard to get into that area and determine the problem.
  7. Ditto the cautions regarding WD-40 and camera equipment. The two should never get any closer than being in the same house. The very properties that make WD-40 so useful for the intended purposes also make it one of the worst possible things to put on a camera or lens: it spreads along surfaces readily (it's sometimes referred to as a polarizing oil) and creeps into nooks and crannies; and it dissolves some adhesives, making it great for cleaning residue from old duct tape, and breaks down some plastics.
    I recall meeting a Leica vendor at a camera show several years ago who made some rather sarcastic remarks about a well known Leica repair tech who apparently had used WD-40 in servicing, at least for awhile before realizing it wasn't appropriate for cameras.
    The one exception I've made to my own rule was for overhauling an Agfa Isolette folder. The lens helical was greased with that lovely green stuff used by German craftsmen up until the 1970s or so, including in my HW-55 air rifle. After several years the green grease dried into a substance resembling a stiff, brittle plastic. It tended to seize lenses making focusing impossible. With the air rifle I noticed it only when it began spitting out chunks of what appeared to be green plastic. Apparently the Weihrauch factory used it inside the spring piston chamber around the leather piston seal.
    With both the Agfa Isolette lens and HW-55 air rifle, WD-40 helped break down the dried clots. But before applying it to the Agfa, I completely disassembled the camera and soaked only the lens after it was removed from the bellows and camera body. Even then it took a few days of patient soaking in the WD-40 and careful scraping with toothpicks to dislodge the dried grease. Before reassembling the lens I used a solvent to completely remove the WD-40 residue. I didn't want to risk the stuff getting anywhere near the leather bellows.

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