Nikon N75 'Err' Message Successful Repair
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I'm currently working with what looks like a never-used Nikon N75 that shows this error.
What happens is the camera will frequently stop the lens all the way down, both during an exposure and when pressing the DOF preview button. The camera actually detects that something went wrong and throws the 'Err' message.
In this case the camera does not lock up. The 'Err' message clears after the next exposure.
So, to solve this problem, some investigation into the mechanism that sets the aperture during exposure, or DOF preview, is needed.
What happens is the camera will frequently stop the lens all the way down, both during an exposure and when pressing the DOF preview button. The camera actually detects that something went wrong and throws the 'Err' message.
In this case the camera does not lock up. The 'Err' message clears after the next exposure.
So, to solve this problem, some investigation into the mechanism that sets the aperture during exposure, or DOF preview, is needed.
There is a lever on the right side of the mirror box (left side if looking at the front of the camera). This lever is spring loaded and normally all the way up. In the up position, when a lens is mounted, the lens aperture lever engages the camera's lever and the aperture opens all the way up when the lens is mounted.
The Nikon N75 Service manual does not go into detail as to how the camera's aperture lever stops at the correct position. To find more information, I looked back in time to one of the first cameras in which the camera body sets the aperture, rather than the ring on the lens. That would be the Nikon FA.
The FA service manual does give a description and it appears there is a capacitor that discharges and at the correct voltage (corresponding to the aperture to be delivered) an electromagnet halts the progression of the lever, stopping it abruptly; thus setting the aperture for the exposure.
This description is only marginally helpful, as the N75 uses a microprocessor and likely has a totally different mechanical mechanism.
The Nikon N75 Service manual does not go into detail as to how the camera's aperture lever stops at the correct position. To find more information, I looked back in time to one of the first cameras in which the camera body sets the aperture, rather than the ring on the lens. That would be the Nikon FA.
The FA service manual does give a description and it appears there is a capacitor that discharges and at the correct voltage (corresponding to the aperture to be delivered) an electromagnet halts the progression of the lever, stopping it abruptly; thus setting the aperture for the exposure.
This description is only marginally helpful, as the N75 uses a microprocessor and likely has a totally different mechanical mechanism.
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This error is commonly known as aperture control unit failure.
An aperture control unit is difficult to repair and even the dismantling of the camera to reach the aperture control unit is very stressful.
An aperture control unit is difficult to repair and even the dismantling of the camera to reach the aperture control unit is very stressful.
Good, I was looking for some people to chime in here if they had any more info.
With this particular camera, after some disassembly to look for anything obvious, the camera was improved. In fact it appeared to be fixed but then started throwing the 'Err' message again. This leads me to believe there might be something correctable in this camera.
So, knowing it is an "Aperture Control" fault, directed me toward this page though nothing seems to be at all related to a film camera's aperture control unit.
With this particular camera, after some disassembly to look for anything obvious, the camera was improved. In fact it appeared to be fixed but then started throwing the 'Err' message again. This leads me to believe there might be something correctable in this camera.
So, knowing it is an "Aperture Control" fault, directed me toward this page though nothing seems to be at all related to a film camera's aperture control unit.
Fixing Nikon D80 “Err” Aperture Control / Shutter Problem … by David HK September 2018
Fixing Nikon D80 "Err" Aperture Control / Shutter Problem … by David HK September 2018 Symptom: My rarely used 11 years old N...
davidhkblog1.blogspot.com
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Nicholas Lindan
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I had this problem in the field. Flicking things up and down in the mirror box seemed to clear it, but then it started again. Rewinding the film and loading a new spool seems to have cleared it - it has been several years and no re-occurrence (oh, dear, famous last words...).
The problem of your N75 is probably a weak permanent magnet which should hold some mechanics which control the going downwards of the aperture lever in the mirror box.
To fix this you have to change that electromagnet with added permanent magnet in the aperture control unit.
If you have this replacement part, it's a simple job - if not, I can think of no other help.
To fix this you have to change that electromagnet with added permanent magnet in the aperture control unit.
If you have this replacement part, it's a simple job - if not, I can think of no other help.
Excellent, thank you for the reply. I did just review the steps from the n75 service manual to remove the aperture control unit unit, but will probably keep the camera as a parts camera. Sad that this happened to a camera that looks essentially brand new and unused.
Mostly the same parts go defect, unfortunately.
I decided to give this another try. I was going to take the aperture unit out and see if I could repair it.
I started disassembling the camera per the service manual. There is something lurking at the green circle in this picture, but I don't know it yet.
**NOTE** soon after taking that remaining cover off, discharge the flash capacitor (per the manual). My capacitor measured 272v before I discharged it.
I started disassembling the camera per the service manual. There is something lurking at the green circle in this picture, but I don't know it yet.
**NOTE** soon after taking that remaining cover off, discharge the flash capacitor (per the manual). My capacitor measured 272v before I discharged it.
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I actually had the top off and was preparing to disassemble the front and back. Over 50 solder connections. Then I noticed the cold solder joint at the green circle. Indeed that is a connection to the 'faulty' aperture control unit!!
I have gotten the "Err" blinking message on Nikon AF slrs [N75, N90 and F100] when the lens is not mounted correctly.
Here is is with all the screws back in place and ready to go.
In some ways this is easier to work on than a 'classic' mechanical camera. Everything comes apart with a single screwdriver and soldering iron. No oddball fancy tools or special hidden 'tricks' to get it apart.
In some ways this is easier to work on than a 'classic' mechanical camera. Everything comes apart with a single screwdriver and soldering iron. No oddball fancy tools or special hidden 'tricks' to get it apart.
Excellent - congratulations!
The three solder joints next to the cold one look good.
The cold solder joint must have happened when the camera was assembled during production?
Yes, and since it made intermittent contact, it probably passed initial inspection, unless, for the cheaper cameras, they didn't inspect all of them on the way out.
That is two cold solder joints I have encountered. Recall the N55 that was under-exposing, had a cold solder joint on one of the DX sensing terminals.
Good thing is both cameras were easily repaired and are essentially brand new. By the way, the other 14 late model Nikons I purchased as 'not tested' all worked fine. So, after repairing the two, my success rate with the purchases was 100%. (I'm not counting leakng batteries and sticky rubber which were easy to clean).
n80 x 3
n2000 x 3
n90s x 1
n75 silver x 2
n75 black x 3
n55 x 2
f100 x 2
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