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Ronny
Tinkerer
Username: Ronny
Post Number: 2
Registered: 09-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, September 17, 2008 - 07:41 am: | 
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I have a Nikon F which I am trying to restore to working order and the mirror does not return all the down to latch when the shutter is fired. The F parts & repair manual suggests that this might be caused by the main return spring being out of adjustment. The function of this spring appears to be compound in that after the shutter is wound and the spring is held under tension, when the shutter is fired the spring is released raising the mirror then when the tension on the front half of the spring is released the rear half, still under some tension, acts on a pivot to return the mirror to the latched position, except in this case it does not go far enough down to re-latch. The manual gives the proper spring tension as between 600 and 610 grams but as I do not have a proper instrument to check this I hung a coffee can from the lever on fishing line and added small steel washers to it until the lever moved forward, then re-weighed the can but I get inconsistent results. Does anyone know of a more reliable way to do this or perhaps another reason for this particular problem? Thank you. Ronny |
Glenn
Tinkerer
Username: Glenn
Post Number: 421
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, September 17, 2008 - 07:24 pm: |
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The common DIY method of adjusting spring tension is to slowly increase/decrease the tension, until you get reliable operation. It is generally quite easy to fine turn the point of correct operation - once you reach the 'sweet spot' back the adjustment off slightly, then observe the operation. you might have to keep doing this until the operation both looks and sounds correct. I have always found that the sound of operation, gives a good indication that moving 'bits' are traveling at the correct/ incorrect velocity - thus giving an indication on the state of spring tensions.
You should also be aware that due to wear etc, the 'as manufactured' specified tension may not be valid. |
Ronny
Tinkerer
Username: Ronny
Post Number: 3
Registered: 09-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, September 18, 2008 - 08:02 am: |
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Good advice and I thank you very much Glenn. I am an amateur just feeling my way and I was reluctant to try to adjust the spring for fear of ruining the temper or getting lost in the wilderness if you follow me. I tend to make things more complicated than they need be, my wife likes to say that I invent solutions for which there are no problems. Your insight into things having wandered from factory spec is something I had not considered and I will proceed with that in mind. Ronny |
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