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Bomobob
Tinkerer
Username: Bomobob
Post Number: 37
Registered: 10-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, May 31, 2009 - 07:28 am: | 
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I think I must be missing a very subtle nuance of this little guy. I picked on up a while ago, and everything was fine except for the film transport. I opened it up and fixed that, but now when I close it, I cannot get the frame counter to work.
I know exactly what's happening, but I don't know the solution. The frame counter gear gets pushed by one index mark on the first wind, but then the little tab that pushes it doesn't release back far enough to engage in the next cog. Well, it does go back far enough, but it also pull the gear back a tiny bit on the way. What happens is that the index advances on the first wind, but then never again. If you click the counter forward or turn it backwards to tack up the slack, it will advance just one again, then not any more.
My guess is that there should be some good tension pushing down on the counter stack in order to keep the gear from being pulled backward by the friction of the pusher tab, but I can't figure out how. I tried different amounts of bow on the copper spring washer under the gear, but it's always the same.
Now here's the thing. I'm pretty sure that before I took it apart, the counter dial was pretty tight, and it took a good twist with a coin to turn it. Now it's not that tight. I'm sure there are no parts missing, but I'm definitely missing something! |
Rick_oleson
Tinkerer
Username: Rick_oleson
Post Number: 897
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, May 31, 2009 - 07:43 am: |
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There should be 2 little fingers on the dial gear: one that pushes the dial forward, and a second, made of spring material, that clicks in and prevents it from backing up between pushes. It is this second one that is retracted when you open the back to allow the dial to return to zero.
It sounds like when you put the dial back in, you got the gear on top of this second finger instead of engaging it into the teeth on the edge of the gear. Another possibility is that something got bent so that it is in a partly released position and does not fully engage the gear. |
Bomobob
Tinkerer
Username: Bomobob
Post Number: 38
Registered: 10-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, May 31, 2009 - 02:01 pm: |
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This model has a totally manual counter that doesn't reset when you open it. You set the dial for however many exposures your film is, and it counts down to zero as you shoot and wind.
The pushing finger is definitely engaged with the gear, because I can't turn the dial backwards more than just the length of one gear step, and it clickity-clicks as I wind it in the correct direction.
The pusher finger is the same one that clicks in behind each cog, as there is a tiny spring applying pressure to it against the gear.
A picture's worth 1000 words. |
Rick_oleson
Tinkerer
Username: Rick_oleson
Post Number: 898
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, May 31, 2009 - 02:44 pm: |
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As you can tell, I'm not familiar with this model. It still seems like I'm only looking at half the system, though ... this looks correct for the advancing mechanism but has nothing to keep it from drifting backwards. it could be just held by friction, but it seems that an anti-backup pawl would be a much better design at no more cost. Are you sure that there wasn't one there when you started? Barring that, was there any other kind of device to keep the gear from turning backwards? One commonly used device is a coil spring wrapped tightly around a shaft and anchored at one end, so that the shaft can turn in the direction that tends to loosen the coil but not in the direction that tends to tighten it. These tend to have a fair amount of friction in the forward direction, it might explain the tight feel that you said the dial had before. |
Bomobob
Tinkerer
Username: Bomobob
Post Number: 39
Registered: 10-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, May 31, 2009 - 08:18 pm: |
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There's a Japanese site with lots of Fujicas taken apart, and the pix are all the same. That gear rotates freely and continuously on a shaft. I was pretty sure it was just the compression tension of the stack that keeps it from being pulled back. If you cock the shutter, the gear gets pushed clockwise one cog, and just a bit of finger pressure on the brass piece on top, keeps it from being pulled back by the friction of the pusher tab when the tab goes back to its resting position.
But now I'm wondering...
I've played around with it enough to see that if the tab had just a little more travel when it pushed the gear, it would be enough to let it slip back far enough so as to click into the next cog. What's happening now is that even with tension holding the gear from slipping, the tab doesn't go back quite far enough.
The system is pushed from underneath by the film advance system, just a sort of cam action. I'm starting to think that when I fixed the film advance, I may have somehow altered the travel of the cam, and now it's not pushing the gear quite far enough. From what I can see, it's a matter of maybe 5 mils or so.
Time to go in again. |
Rick_oleson
Tinkerer
Username: Rick_oleson
Post Number: 899
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, May 31, 2009 - 08:53 pm: |
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I don't suppose that screw that holds the tab and serves as a spring anchor would be some sort of adjusting eccentric? kind of a long shot wild guess, i don't suppose you could get enough adjustment that way even if it was.... |
Bomobob
Tinkerer
Username: Bomobob
Post Number: 40
Registered: 10-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, June 01, 2009 - 06:29 am: |
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Ha ha! Figured it out.
As I suggested in the last post, I felt that the tab wasn't advancing quite enough, and in fact that was the case.
I removed that whole plate with the counter mechanism. That pusher tab and the metal that it's sitting on are budged by an eccentric cam on the film advance gear. That cam was not turning quite far enough after I repaired that section. All it took was to loosen the screw as turn the cam as far as it would go, which was about an extra degree or so, then re-tighten. Now the cam moves the tab just that tiny extra bit to ensure it always pushes the gear far enough to advance one index, and is always able to travel back along the gear far enough to engage in the next cog. It is indeed the compression of the index counter down through the stack that causes just enough tension so that the gear doesn't get pulled back by the friction of the tab.
Works perfectly now.
Thanks for all the input. |
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