Pentax 67 Pentaprism Meter Problem

[ellisson]

I had a problem with the meter in the pentaprism of my Pentax 67. It stopped working suddenly, I think following a lens change. Thinking it was something with the lens, I went back to the first lens, the 90mm 2.8, but this did not correct the problem. The battery indicator light went on, so I thought a dying battery was not the problem. Nonetheless, I changed to a new battery. I also cleaned the battery and pentaprism contacts to remove any early corrosion that might be present.

Still, no function of the meter. The online manual was not clear about what to do next. Then I found a Pentax users' website that reported taking off the lens and then putting it back on the camera may correct the problem. Sure enough, after a new battery, cleaned contacts, and THEN removing and putting back the lens, it worked! Unfortunately, I do not know which of these maneuvers fixed the problem, and now I am wondering why it is that simply removing the lens restores meter function and by what mechanism this occurs? I don't see any parts on the pentaprism or camera that link meter function to lens attachment. I'd appreciate thoughts of others on this perplexing (at least to me) problem. Thanks!

 

[charjohncarter]

I've never had a problem the was like this, but I know that that chain is very important. So, it has to be engaged.

 

[ellisson]

I've never had a problem the was like this, but I know that that chain is very important. So, it has to be engaged.

Thanks, charjohncarter. I see a tab inside the lens mount opening that rotates clockwise with the lens when mounting, and it provides some resistance. Now I wonder if I had not completely engaged that tab when mounting the lens. Something to be aware of!

 

[aizan]

maybe you removed and then installed the prism while the lens was still mounted? *shrug*

 

[charjohncarter]

maybe you removed and then installed the prism while the lens was still mounted? *shrug*

He is right about this: there is a pattern, how the prism, lens are to be put on the camera (and removed). I can't remember but I do have it one of my 6x7 manuals.

The danger is if you do it wrong you can pull the chain out and then it is to the shop.

 

[ellisson]

Going back to the manuals for both the camera and pentaprism, I do not see anything about doing damage or pulling out a chain when when putting on the pentaprism and a lens in any order. What is stated is that when mounting the pentaprism with no lens on the camera, the next step of mounting a lens sets a coupling pin of the pentaprism with the camera's diaphragm coupling side, required for meter reading. If the lens is on first and then the pentaprism is mounted, the lens has to be removed and then put back on to establish this coupling.

I never removed the pentaprism while in the field with no meter reading. I only changed lenses. According to the pentaprism manual, when changing lenses, the coupling takes place automatically, as the process of removing one lens and replacing with the other suffices to couple the finder and camera.

So there is a sequence if the pentaprism is to be put on the camera. But both sequences - pentaprism first, lens second, and lens first, pentaprism second - are discussed. You have to remove the lens at some point when changing finders. I'm still puzzled, but for whatever reason, I lost coupling temporarily.

 

[hendriphile]

I'm having the same problem. Does anyone know the correct sequence to reestablish the link?

 

[ellisson]

I just spoke with a Pentax 67 repair expert at LeZot, located in Vermont. The sequence is important when removing the pentaprism from the camera because the two chains that convey lens aperture setting to the meter through the camera body are "set". This setting is important for correct metering according to aperture and can be disrupted if the pentaprism is removed with the lens on the camera.

In other words, if taking the pentaprism off the camera, it is important to first remove the lens. Changing lenses alone should not cause a problem unless there is some play in the pentaprism seating on the camera. These do have a bit of side to side play normally, but if there is movement up and down, it could disrupt the connection. This would be like taking the pentaprism off with the lens on, causing the metering problem. The repair service has seen this.

So as others have suggested, my problem may have been one of incorrect sequence of "prism off with lens on" even though I had not "removed" the pentaprism! It may have moved upward and off the contacts just enough to cause the sequencing problem. If it happens again, its in for a check up!

 

[ellisson]

You are probably right, John! Thanks!

He is right about this: there is a pattern, how the prism, lens are to be put on the camera (and removed). I can't remember but I do have it one of my 6x7 manuals.

The danger is if you do it wrong you can pull the chain out and then it is to the shop.