Pentax Spotmatic SP Stuck Mirror

DannyC71 · Nov 12, 2024

I have a newly acquired Pentax Spotmatic SP, and it seems okay except that the mirror sticks up. It’s not sticking to the bumper foam as there doe seem to be any. I seem to have borrowed down the culprit but am not sure how to fix it. I took the base plate off and see the mechanism. First photo is where the latch should be when the mirror is down, second is with the shutter cocked, and the third is how it ends up after I press the shutter. The latch just isn’t moving out of the way when the shutter is pressed. If I nudge it myself the mirror comes down.

TIA for any suggestions.

vandergus · Nov 13, 2024

The small gear on the bottom left is connected to the closing curtain. As it travels across the frame, it turns the larger gear, the gear with the little nub on top. When the closing curtain reaches the end of its travel, that nub should push the latch and release the mirror. In your camera, it isn't able to push with enough force to release it.

This could be because the curtains have slowed down over time and are no longer providing enough force. Or it could be that the latch's pivot is dirty and has too much resistance. The latch is easier to fix so I would start with that. Take it off, pay attention to how the spring is tensioned. The large gear with the nub is also easy to take off and clean but it needs to be installed in exactly the same position (same teeth meshing with the smaller gear). You have pictures already so that should be doable. Clean the mounting posts and the pivot holes then reassemble. You don't need to lubricate them.

If that doesn't work then the solution gets a little more complicated.

ic-racer · Nov 13, 2024

Rollei copied much of Pentax design, even flaws. On the Rollei the closing curtain brake can be too strong and prevent the closing curtain from coming all the way over.

The camera needs a CLA.

Last three Rollei I got from ebay. All with the same issue you are showing.

Of course, now I have given up my secret to finding cheap cameras on ebay....

DannyC71 · Nov 13, 2024

vandergus said:
The small gear on the bottom left is connected to the closing curtain. As it travels across the frame, it turns the larger gear, the gear with the little nub on top. When the closing curtain reaches the end of its travel, that nub should push the latch and release the mirror. In your camera, it isn't able to push with enough force to release it.

This could be because the curtains have slowed down over time and are no longer providing enough force. Or it could be that the latch's pivot is dirty and has too much resistance. The latch is easier to fix so I would start with that. Take it off, pay attention to how the spring is tensioned. The large gear with the nub is also easy to take off and clean but it needs to be installed in exactly the same position (same teeth meshing with the smaller gear). You have pictures already so that should be doable. Clean the mounting posts and the pivot holes then reassemble. You don't need to lubricate them.

If that doesn't work then the solution gets a little more complicated.

Thanks for the info. I got the latch off, but in the process lost both the spring and the little clamp that holds the latch on. I did find the spring, only to lose it again. I do have an F SPF body on the way (I discovered Buyee), so depending on the actual condition it may become cannibalized.

DannyC71 · Nov 13, 2024

Update: Spring located, and after some delicate wrangling and a few choice words the spring and latch are back in, I cleaned the gear and the post for the latch and it’s working good now. The little clamp is still missing and will probably have to be replaced.

vandergus · Nov 13, 2024

DannyC71 said:
Update: Spring located, and after some delicate wrangling and a few choice words the spring and latch are back in, I cleaned the gear and the post for the latch and it’s working good now. The little clamp is still missing and will probably have to be replaced.

The piece that holds the lever on is called a circlip or c-clip or even e-clip. You can buy packs of them for pretty cheap. I think this one is a 1.5 mm circlip.

DannyC71 · Nov 17, 2024

vandergus said:
The piece that holds the lever on is called a circlip or c-clip or even e-clip. You can buy packs of them for pretty cheap. I think this one is a 1.5 mm circlip.

I got the e-clip, and it was 1.5mm. the mirror still sticks at 1/8 or slower, but I can live with that. Thanks again.

250swb · Nov 18, 2024

DannyC71 said:
I got the e-clip, and it was 1.5mm. the mirror still sticks at 1/8 or slower, but I can live with that. Thanks again.

You are experiencing a very common problem with the Spotmatic and it's not really solved by lubing anything because wear has already happened but it can be fixed. Using your photo I'll attempt to explain.

The pivot A wears over time, the spring also gets a bit weaker, hence lubing doesn't do much.

This means as the camera gets old the lever B doesn't move back out of the way enough which you've already found.

The answer is one or other of two things, you can either file a tiny bit off the lever B at the point C, and this allows the mirror lever to clear B, or you can twist lever B down a fraction which also has the effect of opening the distance between the mirror return lever and B. It's stiff metal so if you try bending B down in-situ make sure the post at A is braced and ideally use two pairs of pliers, one to hold B and one to twist the end, otherwise take the arm off.

My method is to twist the lever B, but here is a YouTube video showing how to file the tip down

vandergus · Nov 18, 2024

250swb said:
The answer is one or other of two things, you can either file a tiny bit off the lever B at the point C, and this allows the mirror lever to clear B, or you can twist lever B down a fraction which also has the effect of opening the distance between the mirror return lever and B. It's stiff metal so if you try bending B down in-situ make sure the post at A is braced and ideally use two pairs of pliers, one to hold B and one to twist the end, otherwise take the arm off.

I would not recommend this, as it will make it more likely that the mirror charge lever could slip off the release lever between shots. And then the camera won't fire.

At this point, the OP has done everything they can under the bottom plate. It slightly improved the situation but the curtains are still a little slow. A complete tear down and cleaning is the best solution to get a fully functioning camera.

DannyC71 · Nov 18, 2024

So I saw this before the last reply and tried grinding it down, bending felt way more risky to me. That being said, it’s now functional at all shutter speeds, I don’t even see a visual difference in the appearance of the lever, and I also cleaned the contact for the battery while I was in there so now the light meter is working as well.

Thanks to everyone that replied, much appreciated.

I also have an SPF that doesn’t have this issue at all.

250swb · Nov 19, 2024

DannyC71 said:
So I saw this before the last reply and tried grinding it down, bending felt way more risky to me. That being said, it’s now functional at all shutter speeds, I don’t even see a visual difference in the appearance of the lever, and I also cleaned the contact for the battery while I was in there so now the light meter is working as well.

Thanks to everyone that replied, much appreciated.

I also have an SPF that doesn’t have this issue at all.

Well done, it's a simple fix and takes into account the parts are already worn and which a tear down and re-lube isn't going to address. And if a Spotmatic costs £60 on eBay there is no way other than a sentimental attachment to pay far more sending it to a camera tech.

vandergus · Nov 19, 2024

250swb said:
Well done, it's a simple fix and takes into account the parts are already worn and which a tear down and re-lube isn't going to address. And if a Spotmatic costs £60 on eBay there is no way other than a sentimental attachment to pay far more sending it to a camera tech.

Wear is not an issue here. The pivot has not lost any material or become misshapen. It's a very low force interface and I just don't see how it could've changed by any measurable amount. And I also don't see how losing a couple thou off the diameter prevents it from moving.

Filing the top of the lever helps it release but it comes at the expense of the stability of the camera. It is now easier for the lever that charges the mirror to slip off the release lever, a problem that Spotmatics are already known for. And now it's more susceptible.

Pretty much every mechanism in the Spotmatic can be restored through disassembly and cleaning and only a few require lubrication (not this one). I get that completely tearing down a camera to clean the internal mechanisms is not for everyone, but this is not a good solution.

DannyC71 · Nov 19, 2024

250swb said:
Well done, it's a simple fix and takes into account the parts are already worn and which a tear down and re-lube isn't going to address. And if a Spotmatic costs £60 on eBay there is no way other than a sentimental attachment to pay far more sending it to a camera tech.

Thanks

250swb · Nov 20, 2024

vandergus said:
It is now easier for the lever that charges the mirror to slip off the release lever, a problem that Spotmatics are already known for.

That's some pretty rough treatment you are giving a Spotmatic for it to do that. I think one of the enduring things I'm finding on this forum is that people have a hard time visualising a very small thing, everything is overblown and in this case we are not talking about getting the bench grinder out but using a needle file sparingly. Removing a very small amount of metal compensates for the arm rotating further over the years and puts it's stop position relative to the mirror lever back to how it was when new. And that is the point, the rest of the camera isn't new so if a CLA includes replacing all the bearings, posts and springs then fine, you won't need to do this fix, but how likely is that in the 'real world' of sub-$100 camera repair?

Pentax Spotmatic SP Stuck Mirror

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