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11-05-2016, 04:59 AM   #1
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6x7 film advance issue

Hello, I have an issue with a newly aquired 6x7. Sometimes when winding the film advance lever the mirror will raise fully. When pressed, the shutter will release and mirror returns to rest position. The exposure of the film is not effected. The MLU works as designed when the camera winds on properly, ie. when the mirror is not pulled up by the advancing lever. With lens removed you can see the mirror move up GRADUALLY as the advance lever is wound on. It's an intermittant problem but I've noticed the lever which operates the aperture (in the mirror box) is a little sluggish and if not fully up after shutter activation, the mirror raises with the next wind on, anybody see this before???

11-06-2016, 08:23 PM   #2
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That is not right. The film wind-on lever has nothing to do with raising or lowering the mirror, only pulling the film across the film gate after the exposure. Mirror up/down movement occurs in sync with the exposure at the shutter: the sequence is thusly: press the shutter, mirror rises, shutter opens/closes, mirror returns to viewing position. All this is makes quite a din. The MLU lever should raise the mirror immediately it is tripped. That done, you then trip the shutter, which will process as per the line above (shutter opens/closes, mirror returns...).

I don't think it is a battery-related problem, but something is not quite right under the skin. You could try a fresh battery, but if this odd behaviour of the film wind-on persists, it's time to take the beastie to the Doctor.
11-07-2016, 05:03 AM   #3
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QuoteOriginally posted by Silent Street Quote
That is not right. The film wind-on lever has nothing to do with raising or lowering the mirror, only pulling the film across the film gate after the exposure. Mirror up/down movement occurs in sync with the exposure at the shutter: the sequence is thusly: press the shutter, mirror rises, shutter opens/closes, mirror returns to viewing position. All this is makes quite a din. The MLU lever should raise the mirror immediately it is tripped. That done, you then trip the shutter, which will process as per the line above (shutter opens/closes, mirror returns...).

I don't think it is a battery-related problem, but something is not quite right under the skin. You could try a fresh battery, but if this odd behaviour of the film wind-on persists, it's time to take the beastie to the Doctor.
Thanks again for your reply. A bit more research and I found that this was a problem seen in M Series, K Series, Spotmatic, SL,P Series, Program A Super A cameras, no reference to 6x7 or 67 however. The camera hasn't operated for many years and is now with a retired camera service technician for some cleaning and light lubrication. I've a feeling the problem might be a latch or cam being a little lazy from lack of use and lubrication. I'll update when I get it back.
11-07-2016, 08:54 AM   #4
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QuoteOriginally posted by irishbeachboy Quote
Thanks again for your reply. A bit more research and I found that this was a problem seen in M Series, K Series, Spotmatic, SL,P Series, Program A Super A cameras, no reference to 6x7 or 67 however. The camera hasn't operated for many years and is now with a retired camera service technician for some cleaning and light lubrication. I've a feeling the problem might be a latch or cam being a little lazy from lack of use and lubrication. I'll update when I get it back.
If the described problem (mirror lift on wind) is common for M, K, P, A, and Spotmatic series, it is news to users on this forum.* I have seen this happen, however, when the wind/cock/release sequence is out of wack on various brands of SLR cameras. If your technician is competent, the problem will be addressed as part of the CLA. Enjoy your 6x7!


Steve

* No sense reinforcing a new Internet "truth" that almost all manual focus Pentax SLRs over a 30 year span are particularly vulnerable to a mirror interlock problem.


Last edited by stevebrot; 11-07-2016 at 09:01 AM.
02-25-2019, 10:16 PM   #5
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QuoteOriginally posted by irishbeachboy Quote
Thanks again for your reply. A bit more research and I found that this was a problem seen in M Series, K Series, Spotmatic, SL,P Series, Program A Super A cameras, no reference to 6x7 or 67 however. The camera hasn't operated for many years and is now with a retired camera service technician for some cleaning and light lubrication. I've a feeling the problem might be a latch or cam being a little lazy from lack of use and lubrication. I'll update when I get it back.
Reviving this old thread... @irishbeachboy, did you ever get the mirror up on film advance issue resolved? A friend is having this same problem with his 67.

Last edited by murrelet; 02-26-2019 at 03:56 PM.
03-04-2019, 03:30 PM   #6
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QuoteOriginally posted by murrelet Quote
Reviving this old thread... @irishbeachboy, did you ever get the mirror up on film advance issue resolved? A friend is having this same problem with his 67.
@ murrelet, It needed a complete overhaul, there was corrosion inside the camera, I got it back in working order thanks to parts from other cameras! That's not to say your friend's camera needs an overhaul, best let an expert have a look.
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