RZ backs reporting incorrect ISO

[polyglot]

I've recently been using an AE prism and found that 2 of my backs report the correct ISO, but one reports 800 and another reports 50 when set to 400. They do this consistently with respect to back rotation, so it's not the back-to-body contacts.

Has anyone disassembled an RZ back to clean the ISO-wheel contacts? Is there anything I need to be wary of, i.e. are there any critical adjustments in the reassembly that could cause my film-plane to be misaligned or the back to leak? It doesn't look like it to me but I thought I'd be sure.

thanks...

 

[EdSawyer]

mechanically they are not too complicated, I suspect they used fixed resistance to set ISO. That's how most of the RZ electronics work, e.g. how the apertures are conveyed, etc. mamiya USA is pretty good about supplying detailed exploded diagrams on stuff and service manuals are out online for free in many cases.

 

[brucemuir]

You aren't using rechargeable lithium batteries are you?

I don't even know if they make a rechargeable 4sr44 type battery but I recently ran into problems on a contax 645 with a cheap rechargeable.

The voltage was higher than spec and threw the frame spacing off on the contax backs. The contax back has automatic spacing unlike an RZ.

Thought I'd mention it just in case.

 

[polyglot]

I'm using a 4SR44. As I said, two of the backs are fine and two are reliably wonky so I think it's just a bad contact.

Guess I'll have to just pull one apart and start cleaning!

 

[m7olb]

never had this issue before ,just in case you decide to dig deeper ....

Mamiya RZ67 Professional Camera Repair Manual

 

[EdSawyer]

Also, the backs are cheap enough on Ebay , that if 2 are impossible to fix, just save them for parts and buy a couple others.

 

[polyglot]

thankyou so very much for that manual, it's exactly what I needed!

 

[Photo Engineer]

I have had exactly the same problem among my 3 backs. Cleaning the contacts fixed the problem. These are the gold contacts on both the camera body and on the backs. They get a little dirty and also the springs fail to force contact so a little cleaning is in order to eliminate the problem.

PE

 

[mindwar]

anyone still have the RZ manual? would greatly appreciate it

 

[StephenT]

anyone still have the RZ manual? would greatly appreciate it

me too!

 

[EdSawyer]

I posted the half-dozen repair manuals and diagrams I have for the RZ up here:

http://www.edsawyer.com/lenstests/ - there's 3 for the RZ67 body and such, one for an overview of the shutters, one for the 37mm lens and one for the 250 apo lens. those were the ones I have handy, in PDF form. I have some others in printed form or possibly other PDFs, and I can scan/post those sometime soon.

hope that helps.

-Ed

 

[mindwar]

excellent! just what i was looking for! if i dont mange to solve the problems in any other way this will help for sure when opening it up.
cheers!