Hi guys. May I be so bold as to ask a question in what is without doubt the best Pentax forum on the 'net

I have recently acquired a lovely Penatx SV that the seller assures me had a CLA a short white ago and I have to say that the mechanism is buttery smooth but there is one issue that bothers me. When I gently press the shutter button the mirror flips up and unless I continue to press the button the shutter will not fire - i.e. I have mirror-lockup. If I continue the press the shutter fires as normal and the mirror returns. An SV was my very first SLR back in 1965 but I don't remember this happening with that but 1965 is a long time ago and my memory retrieval system aint that good anymore.

Years ago, this is a technique I have occasionally been able to use on some cameras when using slow shutter speed where no mirror-lockup function was available but I can do this every time with this camera. Now I don't have an problem with this other that wondering if it is an undocumented function with the SV or if it is a warning of an imminent malfunction so may I ask if anyone has had this 'problem' or might have further information on it?

Thanks

Keith

[ismaelg]

Hello,

My understanding is that the S1 introduced a mechanism for half press shutter button but to close the diaphragm of the lens, not to lock up the mirror. This was for depth of field preview. It was used in S1 and S3 but quickly abandoned. According to Gerjan's book it was left out on late models of the S1. A possibility is that your camera either was made in the brief time this feature was added, or it may have been serviced with S1 parts during its lifetime. Apparently it never worked reliably and was abandoned. That may explain why in yours it activates the mirror. Does it also activates the pushbar for the lens pin?

Thanks,
Ismael

Thanks for your response Ishmael and yes, this first bit of button travel does operate the diaphragm activation plate as well as flipping th mirror up.

My Pentax technician came back off holiday today tells me he thinks it is a known issue with the shutter box but would need to inspect it to be sure. I'll get the camera off to him when I can and report back here in due course. He has a big backlog of work so it may be some time.

UPDATE: I had my SV serviced and CLA'd and I'm pleased to say that the problem/cause was confirmed and resolved. The film wind-on is buttery smooth and and almost silent whilst the tripping the shutter results in perfect operation of the mirror and shutter mechanism accompanied by a very muted click as the exposure is made. The camera is now almost as perfect as my first SV which I bought in 1965 and served me well for many years.