Your are correct about the A contact hypothesis. It used to be mechanical, now it appears to be electrical in the FA lenses. It just creates an electrical short between the contact pin and the body. So somewhere under the aperture ring or the mechanics behind it, there must be a switch, which when the lens is placed in the A position, shorts out the contact center to ground. I've measured this with my multimeter before.
John Francis wrote:
[reposted becuase I messed up the subject line the first time]
I've got a problem with the "A" contact on one of my FA lenses, and I was wondering if anyone on the list could help.
Basically the camera doesn't recognise the fact that the aperture ring is in the "A" position, so I can't use shutter priority modes.
From perusing Boz's K-mount site it looks as though the problem issimply with the "A" contact. The description of that contact for the KA-mount describes the lens contact as physically moving when the aperture ring is moved to the "A" position to make or break contact with the camera body.
As far as I can tell this isn't true for later (F and FA) lenses, so I assume the switching is done elsewhere in the lens, rather than by moving the contact.
Can any list member confirm or deny this hypothesis? I haven't seen my multimeter for years, so I don't know whether I'll be able to do any further checking myself.
I'd also like to know what the likelihood is that this could be something I could repair myself, something a typical neighbourhood camera repairer could fix, or something that will have to go back to Pentax.
