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06-16-2021, 01:45 PM   #1
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Pentax Spotmatic: intermittent "missing" frames.

Hey all!

I have noticed that during past few years my old Pentax Spotmatic SLR has started misfiring occasionally. On such misfire event, after actuating the film advance lever and firing the shutter a hollow metallic *SNAP* sound can be heard but there is no mirror movement at all. Only a new film advance lever actuation can solve the problem. Usually I tend to get one or two misfires per film roll.


I managed to record the misfire and published it on this Youtube video:



Any hints or advice regarding fixing this problem would be greatly appreciated.

Thanks in advance.

06-16-2021, 05:36 PM   #2
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reckon get in the bottom and blow it out and likely give it a tiny bit of lube and work it away
06-17-2021, 06:24 AM   #3
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QuoteOriginally posted by artrasa Quote
Hey all!

I have noticed that during past few years my old Pentax Spotmatic SLR has started misfiring occasionally. On such misfire event, after actuating the film advance lever and firing the shutter a hollow metallic *SNAP* sound can be heard but there is no mirror movement at all. Only a new film advance lever actuation can solve the problem. Usually I tend to get one or two misfires per film roll.


I managed to record the misfire and published it on this Youtube video:


https://youtu.be/pH6xtk4ZnA0

Any hints or advice regarding fixing this problem would be greatly appreciated.

Thanks in advance.
I have had many cameras do this. The mirror is sticking up due old tired lube. Open bottom and use a toothpick to apply a little sewing machine oil to the gears. This usually works along with exercising the camera.
06-17-2021, 07:20 AM   #4
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Depending how handy or confident you feel either try that of send it for a full CLA,
Mine came looking better than it had in the last 20yrs

06-17-2021, 01:08 PM   #5
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QuoteOriginally posted by arnold Quote
I have had many cameras do this. The mirror is sticking up due old tired lube. Open bottom and use a toothpick to apply a little sewing machine oil to the gears. This usually works along with exercising the camera.
Thanks all for your hints. I'll try to take a look if there's something I could clean in the bottom of the camera. Let's hope a clean-up would get rid of the problem.

I don't have any sewing machine oil. Would it be okay to apply e.g. tiny amount of WD-40 with a toothpick? Or is that stuff too thin and runny?


However, in my case the mirror is not sticking anywhere during misfire because it stays down all the time. In other words when I'm looking through the viewfinder and get a misfire, I don't see any mirror movement at all. There's only the hollow metallic *SNAP* sound (check the video after 00:25).
06-17-2021, 04:08 PM   #6
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QuoteOriginally posted by artrasa Quote
Thanks all for your hints. I'll try to take a look if there's something I could clean in the bottom of the camera. Let's hope a clean-up would get rid of the problem.

I don't have any sewing machine oil. Would it be okay to apply e.g. tiny amount of WD-40 with a toothpick? Or is that stuff too thin and runny?


However, in my case the mirror is not sticking anywhere during misfire because it stays down all the time. In other words when I'm looking through the viewfinder and get a misfire, I don't see any mirror movement at all. There's only the hollow metallic *SNAP* sound (check the video after 00:25).
Have a look at this youtube clip. There are many other clips you can look up as well. I'm not suggesting grinding in your case, since a bit of lube may do the trick.
WD40 is not a lubricant so much as a water dispersant - not recommended. Any thin oil such as 3 in 1 could work. It may be a good idea to use the toothpick to first drop some solvent (isopropyl or lighter fluid type) onto gummed up cogs. Be very sparing and don't use too much.

Here is a better suggestion.

Last edited by arnold; 06-17-2021 at 04:17 PM.
06-17-2021, 10:16 PM   #7
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Check to see if the lever with the spring through it moves toward the front and stays there. If the lever doesn't stay, check to see if the cocking lever pushes the spring lever a little past where it needs to be. If the spring lever locks in place the mirror box is cocked and ready ( the mirror box fires the shutter). If the cocking lever pushes far enough but the spring lever does not stay it means that the levers on the mirror box need lubrication. If the cocking lever doesn't push far enough a little bending of the cocking lever can help. TMI?

06-18-2021, 11:16 AM   #8
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Hi, I hope you had a fine day today!

Tonight I did some more testing with the Spotmatic. After some 20...30 shots, the camera misfired as usual. I immediately opened the bottom plate of the camera and took a photo of the positions of the mechanisms. The "spring lever" that pentaxus mentioned is in its normal (uncocked) position after a misfire. The lever doesn't seem to get jammed like in that Spotmatic F Youtube video.

Then I just re-cocked the camera and the shutter tripped happily again like nobody's business.

Here's two pics that show the mechanisms. Sorry for the second pic, I missed the focus a bit on that one.

Misfiring Pentax Spotmatic - Album on Imgur
06-18-2021, 12:41 PM   #9
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I have a Zenit 212K that does that. I found that if I do not advance the film firmly - all the way to the stop - is when it happens.

I would check that before digging into anything.
06-18-2021, 01:11 PM   #10
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QuoteOriginally posted by Huss Quote
I have a Zenit 212K that does that. I found that if I do not advance the film firmly - all the way to the stop - is when it happens.

I would check that before digging into anything.
That's an excellent point and it really made me think. There's indeed a possibility that all the mechanisms aren't being fully engaged with just a single turn of the lever. And that's what I have been doing for many years. I'm going to test it tomorrow by doing it with two or more turns.
06-18-2021, 10:40 PM   #11
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Could it be so simple as a drop of oil??
06-20-2021, 07:04 AM - 1 Like   #12
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Today I'm happy to confirm that the misfire is indeed caused by a user error! I found that it's possible to crank the film advance lever enough to get the red dot indicator visible, but still not quite reaching the end stop. When I try to trip the shutter, there's that annoying SNAP sound, shutter doesn't fire normally and the mirror doesn't move at all.


Good old case of PEBNAC (Problem Exists Between Neckstrap And Camera)
06-21-2021, 01:51 PM - 1 Like   #13
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You're welcome.
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