SX-70 has Shadowing in Split-Screen

[bastian786]

Dear all,
after reading a lot in this helpful forum, I want to address my first own question.

I am quite skilled in the use and maintenance/ repair of Kodak Retinas (viewfinder and reflex models) and wanted to try something new- a Polaroid SX-70. I got two of them with a lot of other stuff for a fair amount of money. Unfortunately, one of them has kind of a shadow in the lower half of the split-screen focus. The lower half with the shadow is aligned with the rest of the image and I can align the upper half of the circle with the rest of the image to focus- so this is more of a cosmetic issue. Nevertheless, I am interested in fixing this. Google and the repair manual did not help me. My first approach was to have a look at the Fresnel mirror to see if this is caused by dirt or residues but everything is clean. Please see the file attached.

Does anyone have an idea how to fix this?

Regards
Bastian

 

[robert blu]

I have this sporadic, very rarely on one of my sx-70 no idea what causes it.
Welcome to RFF

 

[Godfrey]

The way I fix problems with a Polaroid SX-70 is to send it to MiNT camera for an overhaul. It's a complex, unusual camera that i don't have either the tools or techniques to work on: I let people with that expertise do the job.

If one of the split prisms is out of alignment, it likely means the mirror is slightly out of alignment with the viewfinder optical system and/or the split image prism section has come loose (...conjecture on my part). The viewfinder optical system images into a completely virtual image and it all has to be properly aligned for it to function correctly. I have no idea how I'd check that alignment without the required jigs and test equipment.

G

 

[sepiareverb]

I agree with Godfrey, these are complicated innards, and likely very difficult to get back together.

 

[Kai-san]

This could be caused by the erecting link, i.e the metal bar on the side of the camera which holds it in the open position. If it's not fully locked, or it's bent or the spring on the top of it is damaged this will have an impact on the viewfinder and optics system generally. I have a copy of the service manual but not the very best quality, some of the charts are unreadable. PM me if you would like to have it. Many of the optical adjustment on the SX-70 requires special tools, so it's not straightforward.
Polaroid Originals (Impossible) do also have a service department, they did a great job on my SX-70 Alpha 1.

 

[bastian786]

Thank you for your answers. I guess I found what causes this problem. I have another SX-70 with a perfectly working optics system. If I push the Fresnel mirror a bit upwards, I can cause the same shadow in the lower half of the split-screen and also in the upper half if I increase the distortion. My educated guess is, that something prevents the Fresnel mirror to sit completely flat in the rest position.

I am not willing to send it in for repair, because I have two functioning SX-70s (which I repaired) and I am positive that I can fix this on my own (and better understand how the camera works and improve my skills).

Thank you, Kai, I have this low-quality PDF already. The erecting link is fine, already checked this.

Regards,
Bastian