Nikon F3 Repair Got Me Scratching My Head

I have been repairing these F3 bodies for over 10 years now and have run into something I have never seen before and can't seem to repair. This post is only for the experienced ones with some working knowledge of the inards of this camera.

Upon initial inspection the camera would not fire with the top shutter button, but would with the mechanical release lever - not an unusual situation for these bodies. The advance arm will wind and cock the shutter, only to be released only by the mechanical lever. I pulled the bottom plate, along with the battery box to inspect the wiring, etc. Battery chamber was clean and all wires appeared to be intact. Upon insertion of two new batteries, the voltage measured on the flex circuit board where the two battery wires are soldered measured 3.15 volts. So the power supply seemed ok.

I then removed the top right plate to inspect the shutter release button, on/off switch, and even further down into the 2nd curtain release magnet, etc. Nothing appeared out of the ordinary. I cleaned everything, including the magnet contacts just to be sure. Reassembled and still the same problem.

I then attached an MD-4 with new batteries and it would not fire either. However, the mechanical release would still work. Now it gets weird. Every time I use the mechanical release mechanism, it fires the shutter exactly two times in succession (with the MD-4 on S mode). After doing this repeatedly for about 10 reps the MD-4 suddenly kicked in and started to fire the shutter. Both single and continuous modes worked. Then suddenly the shutter button on top of the camera began to work as well. I immediately removed the MD-4 and the shutter button continued to fire the shutter as it should, on all speeds. However, if I would set the camera down and let it rest say for 2 or 3 minutes, then attempt to use the shutter button again, it would not fire. It acted just like when I initially got it. I have repeated this chain of events and it always works the same. So clearly the magnetic shutter release is functioning.

I then removed the power transfer switch on the bottom of the camera. That is that thing under the black motor drive cap with all the pin contacts that switches the power from the internal batteries of the camera to the motor drive power supply. I have some new parts in store so I replaced the entire assembly. Still the same problem with sporadic functionality.

I then split open the camera and removed the front plate, exposing the entire insides of the camera. I checked all the mirror functions, shutter mechanism and even removed and cleaned the 1st curtain magnetic release. Everything seemed ok and all measured voltages are correct. I then re-assembled only to have the same problem persist. I also checked the FRE and it is good. At times everything works just fine, then when I let the camera sit for a few minutes and it all stops.

Anybody have any ideas, no matter how hair brained they are? Matt

I've moved this to the Camera Repair sub-forum, and added a "Repair" reference to the title.
I hope a solution emerges.

Is current draw within spec?

Yes it is. I still think there is an intermittent short somewhere but can't seem to find anything of note. Why it stops working when it just sits there for a few minutes is difficult to understand.

Matt Hall said:

Yes it is. I still think there is an intermittent short somewhere but can't seem to find anything of note. Why it stops working when it just sits there for a few minutes is difficult to understand.

Click to expand...

Time lapse - maybe a capacitor is discharging where it shouldn't?

You probably know the usual sources with error descriptions. Here just for anyone who is interested:



I also have the C & C Troubleshooting Guide Electronics for the F3 with detailed description of the circuit and troubleshooting.

Please contact me via PM if you are interested,

I thought those that responded might be interested in knowing that I found the problem with my F3. This was not originally my camera (although I have no recollection where I purchased it), so I do not the entire history of this body. I had a suspicion that this was not an electrical issue as it would work on and off with no apparent pattern. Of course it was an electrical issue as no signal was getting the the shutter to begin the exposure, but it was not the root cause as you will see.

I started to focus on the upper body just under the advance arm/speed selector which houses a lot of the shutter release mechanism. After removing the advance arm, shutter button, speed selector dial, top right cover, shutter speed selector itself, and the advance mechanism with frame counter I was able to get a better view of everything. After a lot of searching I discovered that there was a piece of debris floating around the area of the shutter spring and 2nd curtain magnet. This spring is what the shaft of the release button presses down on, part way for metering and fully to release the shutter. In that exact area I found what appears to be a small piece of felt wedged in there. It is not factory spec so I have no idea why it was there, and it was definitely not foam. This piece would migrate around blocking the shutter spring from reaching its contact point. That is why I never got a meter reading or a shutter release. Then I noticed that the plastic dust cover over the 2nd curtain magnetic release was missing (which is there to keep debris out of the magnetic switch). Obviously, somebody had been in here before and mucked the entire thing up. Pieces of this felt material were also found in the magnetic switch area keeping the arm from making any contact with the magnet. That is why I had no shutter speeds, everything was always at the same fast speed no matter where I had the speed selector dial placed. The magnet could not reach the control arm to keep it in place before releasing at the correct time to make the exposure.

I removed all the debris and cleaned everything within an inch of its life. I had a spare magnet dust cover which I inserted as well. After replacement of all the parts I had a fully functioning camera , WITH accurate shutter speeds! I guess as I would experiment with this while trying to get it to work I was moving the camera around and the debris would sometimes move out of the way and everything would work, only to eventually fall back into position to block everything.

I now have 2 F3 bodies left that are non-functioning and I fear that is how they will stay as pieces of the flex circuit board are damaged. I guess I shouldn't complain to much as I have 62 more bodies that have been repaired, and fully restored to Mint or better condition. All have been shutter speed tested and work great. Also done the same to my 6 F3AF bodies. Now I plan on moving on to my F2 collection and see what I can do there. You may be hearing from me again as I jump on that steep learning curve for a new camera.

Whew! Impressive diagnostics ... and persistence! Kudos!

Excellent expertise, thank you!

Given that F3 is better sealed against dust and moisture than most other film cameras, that's a surprise.

F2 ought to be a breeze by comparison.