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Wernerjb
Tinkerer
Username: Wernerjb
Post Number: 285
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, March 13, 2008 - 06:11 am: | 
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Has anyone ever had the Hi-mATIC 7's film winding ratchet system apart? How is the winding shaft stopped from rotating the wrong way, which makes winding and cocking the shutter impossible (I have actually replaced the dysfunktional one with one salvaged from a Hi-M 9, incl. the take-up spool, but would nevertheless like to know how about the old one's function)?
Thanks for responding, W. |
Wernerjb
Tinkerer
Username: Wernerjb
Post Number: 289
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, March 19, 2008 - 10:05 am: |
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Is there really nobody out there who knows how to prevent the movement of the entire shaft when only the inner part is supposed to move (turn anti-clockwise) when transporting the film?
The camera itself has been reassembled with the spares from a donor Hi-M 9, but I am still curious to find out what was wrong with the dysfunctional original mechanism, W. |
Dan_mitchell
Tinkerer
Username: Dan_mitchell
Post Number: 8
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, March 19, 2008 - 10:59 am: |
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I had to take one of those completely apart once, but it's been a while. As I recall, the ratchet and pawl on the bottom control the winding movement. There is a somewhat circular peice with steps on it that couples the winder to the shutter. The design of that allows partial stroke winding. I've noticed that piece can wear and cause problems, too. The little spring on the pawl is easy to displace when you take the bottom cover off since one leg sits against the body. I also recall there is a gear that reverses the winder motion and that gear is held in place with a LH screw. I remember, because I twisted the screw head off first time I worked on one of those.  |
Dan_mitchell
Tinkerer
Username: Dan_mitchell
Post Number: 11
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, March 19, 2008 - 08:10 pm: |
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Hi Werner, Your question got me curious so when I got home tonight I pulled the bottom off of a Hi-matic 7 to look. As best I can tell, friction between the wind shaft and the large collar on the bottom turns the first gear. Once the shutter is cocked and locked in place, the friction is less than the force on the gear from the ratchet pawl and the winder rotates back without affecting the gear position. The collar screws onto the shaft and is held in place with a small setscrew. So, (if I understand your question) it looks like the entire shaft is supposed to turn in both directions, with only the friction between the collar and gear controlling things. (?)
Possibly the gear teeth and/or pawl was worn to the point it wouldn't hold any more. |
Wernerjb
Tinkerer
Username: Wernerjb
Post Number: 290
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, March 20, 2008 - 09:59 am: |
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Hi Dan, thanks a lot for what you did to find out.
You wrote "Once the shutter is cocked and locked in place, the friction is less than the force on the gear from the ratchet pawl and the winder rotates back without affecting the gear position."
This is a good description of how my functional Hi-M's work, except this rather early model 7 before I put in the spares from a derelict Hi-M 9. Which renders the Hi-M 7 no longer authentic. The old wind shaft was like welded together at the bottom end (and it still is), so when cocking the shutter it would turn only in one dirction, a lot of tension was built up, but quite logically the movement was stopped before the end of the shaft's travel. It was then neither possible to cock the shutter nor complete the winding. A previous owner had used too much force and moreover loosened all the screws, so that the circular piece with steps had even lost its typical shape. It was quite difficult to put everything back in and find the default position of the shaft.
What I had in mind when I asked for help was that I thought the mechanism had a different way of working properly, as also the parts used in this Hi-M 7 are somewhat differently dimensioned compared to its later siblings in the model line. The meter cell looks like a small vacuum tube, the meter is differently fastened to the body, the winding shaft has another friction "brake" (the one that worries me so much!) and also the plastic part of the take-up spool has a different inner diameter. Even the screws on the shutter cover (Seiko LA) seem different. This is to say the hacking of parts is not possible in any case, instead of parts you have to swap the whole component.
Thanks again and I hope you don't mind me expressing my gratitude for the outstanding repair tips on your excellent repair page, which I find VERY beneficial, W. |
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