Mamiya 6 folder rangefinder issues

So I bought a junky, but functional, Mamiya 6 folder. The glass looks really clean but unfortunately the rangefinder was way misaligned. I spent quite some time aligning it to infinity, which worked for a second.
I found that when the camera was shaken, bumped or even just knocked a bit, the rangefinder would go back out!
Does anyone have experiences working with these rangefinders, or some idea as to why it's so unstable? Help!

Thanks!!

cfrye said:

So I bought a junky, but functional, Mamiya 6 folder. The glass looks really clean but unfortunately the rangefinder was way misaligned. I spent quite some time aligning it to infinity, which worked for a second.
I found that when the camera was shaken, bumped or even just knocked a bit, the rangefinder would go back out!
Does anyone have experiences working with these rangefinders, or some idea as to why it's so unstable? Help!

Click to expand...

I've adjusted a few. All the ones I've adjusted have had a set screw for gross rangefinder adjustment, which pushes against a small strip of metal on the rangefinder arm, which in turn comes into contact with the rangefinder cam. I've always thought that contact between the metal strip and the cam was pretty touch and go, so maybe your rangefinder arm is loose or out of alignment, and a bump knocks it off the cam ? In general I'd check for any wobbly bits that might throw it out of whack if they slipped.

It happened to me with another rangefinder folder the mirrors unglued and they were just hold in the rails, any movement or small bump to the cover made the mirror moves and misalign the rangefinder.