Help diagnosing a malfunctioning D40

FocusDave · Feb 29, 2012

As it turns out, I have in my possession a malfunctioning D40 that was acquired for a very small amount of money. The issue with it is that you can't stop the lens down past its maximum aperture. When you attempt to take a picture at anything besides wide open you get an err message. In addition, images taken at wide open in aperture priority are horribly underexposed, even though the camera is indicating a correct exposure. I've cleaned all of the lens contacts with alcohol already; no dice. It would be nice if I could salvage this body because it only has 7,300 shutter actuations on it.

mommy-medic · Feb 29, 2012

What lens(es) are you using, and does that lens have an aperture lock on it? (I hope I'm not saying something really stupid, I don't fully understand how aperture locks work or why they are on some lenses, but I know on my 50mm I had to lock it before I used it.)

Another potentially dumb question, but have you tried auto instead of aperture mode?

I'm sorry if this isn't terribly helpful, but at least I'm trying.

480sparky · Feb 29, 2012

Does the issue arise using different lenses?

FocusDave · Feb 29, 2012

I've only tried it while using an AF-S 18-105mm kit lens. We have a Sigma 50mm with an aperture ring; I might try that.

Big Mike · Mar 1, 2012

Sounds like a problem with the lens, not the camera at all.

cbrown222 · Mar 1, 2012

You have to leave the lens at the smallest aperture. It's the same with all Nikon compatible lenses. Just use the aperture dial to open up or close the aperture, and once you click the shutter button, the aperture will automatically close to what you set it as. If you didn't have this, the lens wouldnt let in enough light and the viewfinder would be way too dim

TL;DR: Keep it stopped down. The camera will automatically open/close it to the aperture you set.

FocusDave · Mar 1, 2012

Big Mike said:
Sounds like a problem with the lens, not the camera at all.

cbrown222 said:
You have to leave the lens at the smallest aperture. It's the same with all Nikon compatible lenses. Just use the aperture dial to open up or close the aperture, and once you click the shutter button, the aperture will automatically close to what you set it as. If you didn't have this, the lens wouldnt let in enough light and the viewfinder would be way too dim

TL;DR: Keep it stopped down. The camera will automatically open/close it to the aperture you set.

I don't think I'm stating this clearly enough, so let me try again:

The lens I'm using is a lens that is known to work (we use it on our D90 every day). It doesn't have an aperture ring on it, either. Therefore, the only way I have to adjust the aperture is by using the dial on the camera. Whenever I try to take a picture at anything other than wide open (largest aperture), I get an error message.

I will use our Sigma with an aperture ring to see what happens, as well.

KmH · Mar 1, 2012

There is a motor in the D40 (and all Nikon DSLR's) that actuates the lens aperture. I'm betting the motor is bad.

Check the lens aperture adjustment lever on the camera mount -

FocusDave · Mar 4, 2012

^^ That makes sense. Is there any way to for sure diagnose that, and any idea how difficult/expensive to replace?

FocusDave · Mar 5, 2012

I had mentioned before that the exposure for the images I did manage to capture was horrible off, and I now have a number to go with that. The camera's metering is about 6-7 full stops off. It sounds like this body was only worth the $20 we spent on it.

Infinite_Day · Mar 6, 2012

Depends on how much it would cost for Nikon or another repair shop to fix it. If you can get it fixed for not too much it would probably be worth it to keep the body from going to the scrap heap.

FocusDave · Mar 6, 2012

Infinite_Day said:
Depends on how much it would cost for Nikon or another repair shop to fix it. If you can get it fixed for not too much it would probably be worth it to keep the body from going to the scrap heap.

It's not going to go to the scrap heap. We'll actually make a set of disassembly guides that might then help other people who need to fix theirs someday.