Mamiya 645 film advance problem

[TRC]

I recently acquired a Mamiya 645 Pro and sometimes after taking a shot I cannot advance the film. At that point I have to take the film back off, put it back on, and then I can wind the film again. The first shot after doing so is not advanced and I end up with a double exposure. It seems pretty random - not like it always happens at a certain frame but seems to get a bit worse maybe the further I get into a roll. This is with a 120 insert and it does go to 15 before winding out.

Things I've already tried:

- cleaning the 4 contacts with an eraser.
- cleaning the pin with an eraser.

What do you think the issue is, the film back itself or the insert? Or, something else?

Thanks in advance!

 

[MattKing]

Welcome to APUG!

Sounds like a problem with either the double-exposure prevention interlocks or the dark slide interlock.

If you have another insert, see if you can determine whether the problem is specific to one insert. Given the relatively low cost of used inserts, it is worthwhile to have a few.

It could very well be a problem with the dark slide.

Does switching the lever to multiple exposure allow you to advance the film?

 

[TRC]

Welcome to APUG!

Sounds like a problem with either the double-exposure prevention interlocks or the dark slide interlock.

If you have another insert, see if you can determine whether the problem is specific to one insert. Given the relatively low cost of used inserts, it is worthwhile to have a few.

It could very well be a problem with the dark slide.

Does switching the lever to multiple exposure allow you to advance the film?

I'm not sure as I haven't tried that. I only had one insert so trying another has not been an option yet. I did go ahead and buy another back and insert on flea-bay in "EXC++" shape so hopefully that will rectify the situation. I had read multiple reports of people who had dropped their insert and ended up with similar issues which is why I was leaning towards the insert being the issue. At any rate, I'll report back if the new insert alone fixes the issue while used in the original back.

 

[snederhiser]

Hello;
I do not own a pro model but have the earlier 1000s (non removeable back). Last year I had issues with the film advancing. Tracked this down to the film inserts. Had to replace the rubber tire that rides on the film backing paper. The old tires were hard and had flat spots not allowing the proper spacing for the film advance to work. Now I load up the film before shooting to avoid these flat spots on the tire. Hope this helps, Steven.