Sigma Zoom broken?

[Diamond Dave]

Sorry to post this in multiple forums but I'm new and realized this post may belong here instead.

A friend just gave me an old (1985) Sigma Zoom-Master 35-70mm OM mount lens. When I depress the depth of field preview button on the side, I can't see the aperture stop down inside the lens (I've set it at its minimum, f/22). By means of comparison, I can see the aperture stop down on the Zuiko 50mm I have.

So the question is: is it broken? I don't want to waste time or film to find out (e.g., shooting a roll of film, developing it, and learning that yes, the aperture really is stuck wide open).

Thanks.

 

[compur]

Mount lens on the camera, set a small aperture, open the back of your camera,
set a slow shutter speed, point camera at something bright, release shutter
while looking through back of camera.

Did the diaphragm close down?

 

[Diamond Dave]

Mount lens on the camera, set a small aperture, open the back of your camera,
set a slow shutter speed, point camera at something bright, release shutter
while looking through back of camera.

Did the diaphragm close down?

I will try that as soon as I finish the current roll. Thanks; I still think digital and don't realize the camera opens up in the rear!