Canon 7s -- Film Advance

[KoNickon]

I've decided to see whether I can fix this myself -- the camera has been sitting in a box more or less since I got it some years ago. The film advance spool and the advance sprocket are not properly engaged -- the sprocket only begins to turn after the advance lever is most of the way through its throw. The result is that I lose two frames before the shutter is fully charged.

Any guidance you can offer would be great. I also am concerned that getting the top cover off (I assume that's necessary) may be difficult -- lots of dials that have to be removed. And that in and of itself may convince me that I should leave this to a professional. Thanks.

 

[Mackinaw]

The wind mechanism is in the bottom of the camera, so take off the bottom plate first and see what happens when you advance the film.

JIm B.

 

[retinax]

My 7 does that sometimes after rewinding, takes a stroke or a stroke and a half before the wind mechanism re-engages. So it might be the same mechanism that's sticky and doesn't want to return to normal wind function? I'd start investigating there. Maybe first move the collar from rewind to normal a few times, with some winding in between, and observe? AS Mackinaw writes, the wind mechanism is mostly at the bottom. The engaging happens below or inside the sprocket shaft I think. Getting the top cover off also isn't very hard if you've had top covers off other cameras.

 

[KoNickon]

Thanks, good to know that getting the bottom off may be all that's necessary. It doesn't seem like the issue is the wind mechanism reengaging; rather, it's that the wind lever/takeup spool are not meshing properly with the sprocket gearing. Properly, there should be little to no free movement -- the sprocket should start turning at the same time as the wind lever is moved.

 

[KoNickon]

Looking at the camera bottom plate, I realize that the locking assembly for the camera bottom probably needs to be removed before the plate will come off. I don't have a pin spanner that will fit inside the film compartment to unscrew the assembly. Too bad.

 

[retinax]

Looking at the camera bottom plate, I realize that the locking assembly for the camera bottom probably needs to be removed before the plate will come off. I don't have a pin spanner that will fit inside the film compartment to unscrew the assembly. Too bad.

No, you don't need to unscrew the lock. Only the ring around the tripod socket and the two screws.

 

[ranger9]

If seeing an exploded diagram would help, there's one for the Canon 7 on manualslib.com:

https://www.manualslib.com/download/1004337/Canon-7.html

Just don't be fooled by all the inviting big green DOWNLOAD buttons that actually are ads trying to trick you into downloading crapware.

 

[Mackinaw]

This may be of help.

Jim B.

 

[KoNickon]

You were right -- the bottom comes off easily with the removal of three screws. Unfortunately, no access to any gearing from there. I removed the battery compartment but that didn't lead to anything. And I'm definitely not about to go undoing meter and flash synch wiring to see if I can get further into the innards from there.

I did notice that if I hold a thumb against the takeup spool while winding on, to prevent the spool from unwinding, things would work normally. So I wonder whether there's some sort of pawl that prevents the spool from unwinding, that isn't working right?

I'll look at the manual to see if I get any clues. Thanks, all, for your help thus far.

 

[retinax]

Ah now I also see it in the exploded diagram above; sorry I mislead you about the ring around the tripod socket. Didn't expect they changed stuff like that between the 7 and 7S.

 

[Swift1]

So I can't really offer any advice in taking the camera apart, I'm just wondering if the advance/rewind switch is working properly.
When I first got my Canon 7, the advance/rewind collar around the shutter button wasn't secured properly and it would slip a bit when turned.
Is the rewind switch mechanism in the right position?

 

[KoNickon]

Yes, the advance/rewind collar is functioning correctly -- no slipping. Thanks.

 

[Swift1]

Yes, the advance/rewind collar is functioning correctly -- no slipping. Thanks.

I kinda figured that you probably had that covered, but thought it wouldn't hurt to check.
Hope you can get it working.