Lens closing up right at exposure??!?

[blinded]

I have a Maxxum 7000 body with all Minolta AF glass. I changed the batteries in my camera today (I should have done it sooner, the shutter lag is noticeably faster) and I was just testing it out, and once and awhile when I'd fire the shutter and have my lens at say f.2.8, it would suddenly make a clicking noise like a spring (this would happen immediately after I'd fire the shutter) and it looked like it was shooting at something really small, maybe f22 or something like that. This happened many times with both my 50mm and 28mm lenses I tested, so I'm pretty sure it is not the lenses, and it is the body. Probably 1/5 times it would happen. This could explain all the blank frames I'm getting back on my negatives. Anyone have a clue what this is? I have to shoot a gig tommorrow night and I don't exactly have a backup body right now.
If worst comes to worst I can easily find a new body before the show, but it would be nice to know what it is.

[Ads]

[ksmattfish]

Let me see if I understand this...

You are looking through the viewfinder, and when you fire the shutter it looks like the lens is stopping down?

Does the image black out? I don't exactly know what order the following occur in, but with a SLR when you fire the shutter, the mirror should lift (blacking out the viewfinder), the lens stops down, and the shutter opens. Then it returns to it's resting state. If you can see the image the entire time through the viewfinder, then your mirror is not lifting, and that would definately cause a blank frame.

I'd borrow a different camera.

[blinded]

I can clearly see the lens changing aperatures when I look at the camera from the front. (not through the viewfinder) The aperature blades are clearly visible through the front of my lens, and I see them going from 2.8 to 22. Mirror is fine. The camera store gave me a $300 repair price, used 7000 bodies are $200. I'm in some poop.

[havoc]

Open the back of the camera and fire the shutter, do it at different shutter speeds. Make sure your shutter is actually opening when you click it. (and that its opening all the way) With blank negatives it sounds like the shutter is sticking. I have an older canon auto focus that the same thing happened to. Also check the shutter curtain, (without touching it) for goo and dirt/grime.

[mikerfns]

Sound like it may be the aperture stop down magnet, which I believe is a common failure with these older Maxxum cameras. IIRC when it fails the aperture will always close to the minimum f/stop no matter what is set on the body, resulting in SEVERE underexposure which on print films results in an almost clear negative, ie. blank frames.

In any case, NOT a good sign, and these cameras are not really economical to repair.

Mike