Nikon F4 Jittery AF

[hjoseph7]

A few months ago I purchased a Nikon F4 in pristine condition to add to my collection. The camera looked almost brand-new except for a cracked small LCD screen in the viewfinder. Something I could live with. I went through all the checks making sure everything was working right. The AF seemed to be working fine. With a Manual lens the Viewfinder displayed the little red arrows and a bright green dot once the camera focused.  Looks like this camera was a keeper and was not going back to the seller. I smuggly placed the camera in storage waiting for the day I would run some film through it.

Well yesterday was that day. The camera was already loaded with film (Kodak Color Plus 200), so I checked the AF one more time. I had to go to the manual to turn the camera on because I had forgotten. I pressed lightly on the shutter but nothing happened ? I checked the manual again to make sure I was doing everything right then pressed the shutter again, but nothing happened the LCD did not light up at all. Apparently the camera was set to 'S' instead of 'L' which turns it off, so it must be the batteries. Sure enough I checked the batteries and they were drained. The camera had only been in storage for about 2 months, so I said to myself 'Hmmm'.

I replaced the batteries with some new ones and pressed the shutter again. This time the viewfinder lit up ! I could see the film count, aperture, shutter speed etc. I depressed the shutter and the camera focused, (the little grren dot lit up) , but when I tried to focus the camera on another subject, nothing happened ? The AF stopped working or was frozen. I removed the batteries and put them in again, but got the same results, nothing. I then cleaned all the contacts first with a pen eraser, then with a little alcohol. I tried again, but nothing happened again. The camera would focus once, then the AF would shut down. Even in manual mode the little red arrows did not light up. Essentially I could not take a picture because the camera only fires when the little green dot lights up.

I figured the camera probably needed a CLA. Dissapointed, I started looking for a camera repair shop. Nikon camera repair said they did not service that camera model anymore as ususal. I did find a shop in NC that might be able to repair it so I sent them an email. About 2 hours later, I picked up the camera and slightly pressed the shutter after turning it on and everything was working fine ! The AF was working in M, S, and C(Manual, Single, Continuous) !!  

I'm not sure, but it sounds like one of the capacitors is shot, or there is a short somewhere. I checked the camera again this morning and everything seems to be working. This time I made sure to turn the camera off by moving the switch to 'L'.  What a relief, but I'm not exactly confident taking this camera out. Something is up and I'm not sure what it is? maybe the AF can shut down at any time without warning. I wonder if the Seller knew about this and did not tell me ? In any case has anybody experienced something like this with the AF on their camera ?    

     

[ben_hutcherson]

I'm a little confused by your title and the text of your post.

Does the AF currently work? Your post seems to indicate it does, but that you're worried about if it's going to continue. Given your title, I would interpret "jittery" as maybe seeming reluctant to lock or jumping around.

If that's the case, I might suggest recalibrating your expectations. I have two F4s and the AF on both operates similarly, and obviously I haven't used yours so I can't say if yours is normal or not(or if mine is normal, but I'd guess two different cameras from two different sources in different battery configurations operating more or less the same might give me some idea).

Remember that the F4 AF is incredibly primitive by our current standards. For that matter, in 1990 or whenever it came on the market, some people considered it less than great compared to its contemporaries.

I use the AF box in the center much as I would use a split image rangefinder-or in other words I look for something with a defined high contrast vertical line to point it at. If that's not present on my subject, I find something at a similar distance. I've used it enough to be second nature now, but it's also definitely a big step back even from the F5 and I find it less sure than the N90(which is also a single point system).

I find it perfectly normal for the AF to hunt a bit on the F4 in basically any situation other than daylight with strong verticals. In lower light, a flash that can shine a red grid for AF assist can be a lifesaver.

If you really want to test the AF, I'd suggest printing a dark black vertical line on white paper, taking it outside, and seeing how the AF handles it. Of course that's not a realistic real world, but it's about as perfect of a target for the F4 AF.

One last thing-at one point or another I had a camera-I think it was an F5 but don't hold me to that-that wouldn't lock to save its life unless things were nearly perfect. It came to me "smoky"(from a smoker's home) and I suspect that was part of the issue. I CAREFULLY locked the mirror up and cleaned the AF module in the bottom of the mirror box. After removing a decent bit of yellow-brown haze, AF operation was perfect(and the F5 tends to be very sure focusing). With that said, it's worth trying as a last ditch attempt. Tobacco smoke can wreak some of the worst havoc on camera optics, but even just normal day to day dust and other things in the air can cause issues if they're especially bad. I could see this being the case on a "shelf queen", especially if it has spent time without a lens or body cap fitted.

[Jay M]

Try to determine which part is failing by doing this quick - remove DP-20 viewfinder then turn camera on and off, AF/MF focus as usual, of course you cannot see through VF but should be able to tell via the small focusing-aid LEDs on top front of camera body if lit or not right, etc., if works repeatedly without VF, then DP-20 may or may not be the issue due to the cracked small LCD screen in the viewfinder (not sure how but might be from an impact damage before?) or simply the contact pins loose seating connection (hopefully the latter) then you should know what to do next. Good luck.

[bgelfand]

Perhaps you just had something (oxidation?) on the AF mode switch contacts and moving the switch between modes cleared it. If it continues to work, chalk it up to a gremlin that has departed and enjoy the camera. It is not as if your life depended upon that camera working.

Having a working old camera, that does not have a dependable supply of spare parts, worked on can cause more problems than it fixes. Remember the old engineering saying. "If it ain't broke, don't fix it." Right now, "It ain't broke"

[hjoseph7]

Just now, Jay M said:

Try to determine which part is failing by doing this quick - remove DP-20 viewfinder then turn camera on and off, AF/MF focus as usual, of course you cannot see through VF but should be able to tell via the small focusing-aid LEDs on top front of camera body if lit or not right, etc., if works repeatedly without VF, then DP-20 may or may not be the issue due to the cracked small LCD screen in the viewfinder (not sure how but might be from an impact damage before?) or simply the contact pins loose seating connection (hopefully the latter) then you should know what to do next. Good luck.

I should have changed the title to "Inconsistent AF" , although my first choice was "AF does not work" . I tried that, I removed the DP-20 and depressed the shutter button, but it did the same thing as with it on. That is it focused once, then the AF went dead. I also removed the battery pack and cleaned all the contacts, but that did not do anything at first ? Two hours later, the AF was working again. I forgot to mention one thing after I changed the batteries, I think I let the camera sit for about 30 minutes in the ON mode(switch set to "S") . That's when I noticed that the AF was not working right, but the viewfinder LCD was on and working...

[Jay M]

Well, sounds like an AF system issue to me which's not straight forward for troubleshoot while kind of not expected 'cause I have never experienced such an issue myself with quite a few F4 variances in hands over years but it could fail based on a N2020 that I acquired cheap has failed exactly like what you described with an intermittent AF and finally dead out (tried few things myself to save it but no luck) leads to the nice look camera totally useless even manual focusing won't fire although meter still works like a charm, then keep it as parts for myself without bothering to fix or sell, so the F4 from similar or little later era of old AF technology may fail like that probably (sorry to say without absolute certain) and hope you can find a solution to it.

[Rick Helmke]

Is this all happening using the same lens or have you tried more than one? If you haven’t tried multiple lenses then do so. I have two F4S bodies and neither focuses as quickly or as positively as my D4 or 810 and I wouldn’t expect them to do so. I wouldn’t be surprised to find Ben is right, he is quite knowledgeable about this sort of thing. If I recall the F4 came out in ‘86 and I thought then that AF was more of a gimmick than something useful. For sports and many other fast moving activities I’m still not terribly impressed. 
 

Rick H.

[hjoseph7]

10 hours ago, Rick Helmke said:

Is this all happening using the same lens or have you tried more than one? If you haven’t tried multiple lenses then do so. I have two F4S bodies and neither focuses as quickly or as positively as my D4 or 810 and I wouldn’t expect them to do so. I wouldn’t be surprised to find Ben is right, he is quite knowledgeable about this sort of thing. If I recall the F4 came out in ‘86 and I thought then that AF was more of a gimmick than something useful. For sports and many other fast moving activities I’m still not terribly impressed. 
 

Rick H.

No I tried  3 different lenses, the 85mm, 50mm and 35mm (the only Nilon 'G' lenses I have) and they all failed. Not sure how long the AF is going to last, but it does come in handy for my aging eyes and it's the main reason I got this camera. I can play with al the knobs and still have AF which is great. Plus it has the range finder for Manual lenses.