Mamiya 645AF - film back resets to '1' during use

[rippo]

Bought a 645AF a few months ago, and it came with two backs. Within a couple of days of using it, I noticed one of the backs would reset to '1' part way through a roll of film, making it impossible to know how many shots I really had left. It would also do the 'leader wind' action when I next pressed the shutter…actually it's probably the reverse order of those steps, but I wouldn't notice it until the back made the extra-long wind noise. Anyway, I replaced the battery in the back and the problem went away.

It happened again today. I have no idea if it's the same back or the other one, as I didn't mark it (thought the problem was solved). There's no low-battery indication on the back. Is this a sign of low batteries? Is the back door coming loose momentarily, causing the back to think it's loaded with fresh film? Something else? Basically, is this a known problem/feature or do I have a weird back? Thanks.

 

[MattKing]

Are you sure that it is the back - could it not be the insert?

 

[rippo]

It could be the insert…how can I narrow that down? I could swap inserts of course, but this has happened so rarely - so far! - that it's not predictable.

 

[MattKing]

First, I would label each insert so that you can tell them apart. Then I'd label the backs as well.

And then I'd wait until it happens again, to determine which back and insert combination was involved.

Finally, I would switch the inserts (assuming you have just two).

If the problem re-occurs with the same back - that is where your problem is. If it re-occurs with the same insert - that is where your problem is. And if it never re-occurs, your problem is caused by the particular combination of that insert, and that back, in which case I would replace whatever can be done most inexpensively.

 

[rippo]

Ah, you're advocating the patience approach. Crazy, but I guess I'll have to try it! I've labeled the potentially bad back and insert, and will see what happens. Thanks!

 

[brucemuir]

I know I had a funky reaction w/645AFD when the BODY batteries died.

It doesn't appear to store info anywhere regarding film usage, so when I put fresh batteries in the body it either reset the back and rewound or just rewound I forget which.

 

[tnabbott]

Bought a 645AF a few months ago, and it came with two backs. Within a couple of days of using it, I noticed one of the backs would reset to '1' part way through a roll of film, making it impossible to know how many shots I really had left. It would also do the 'leader wind' action when I next pressed the shutter…actually it's probably the reverse order of those steps, but I wouldn't notice it until the back made the extra-long wind noise. Anyway, I replaced the battery in the back and the problem went away.

It happened again today. I have no idea if it's the same back or the other one, as I didn't mark it (thought the problem was solved). There's no low-battery indication on the back. Is this a sign of low batteries? Is the back door coming loose momentarily, causing the back to think it's loaded with fresh film? Something else? Basically, is this a known problem/feature or do I have a weird back? Thanks.

This has happened to me on occasion as well. I have not determined the cause yet either.

 

[rippo]

Bruce: that's odd, because the back should be storing the frame number, ISO etc for you. Perhaps your back batteries are dead, and the back relies on the body batteries to retain the info? (And thus forgets them when you run out of juice there). I haven't had the problem of losing frame count when changing body batteries.

I had a weird instance where the back didn't power up the display when I attached it to the body on a shoot over the weekend. The disturbing thing though is that this was my OTHER back (with different insert). Which might mean something is wrong with the body. Removing and reattaching the back woke it up, and I never lost frame count. Makes me a little nervous, as I don't have another 645AF body.

 

[brucemuir]

Rip.
Try cleaning the contacts on both the backs and where they mate on the body with a pencil eraser or q-tip and Iso Alcohol.

Maybe there some crud messing with communication between the body/backs.

Like you mention, I pretty sure all the back batteries do is retain info for when they are removed or there is an interruption of power from the body.

 

[rippo]

Thanks Bruce. I've cleaned the contacts as per your suggestion. I won't really know if it's fixed or not, since the problem was very intermittent.
-Matt