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Chris
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, April 17, 2004 - 08:06 am: | 
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Hi,
I have two cameras (Pentax Spotmatic SP & Soviet Leningrad) plagued by the same problem: At 1/1000 the shutter curtains don’t open (i.e. the shutter fires, but no light is visible at all through the curtains).
At other speeds, the speeds seem accurate & the curtain speeds regular (computer monitor test) , but with 1/1000 the frame always remains black (also in daylight) or – with the Spotmatic – ½ the frame is exposed if I hold the camera vertically...
Is there an easy fix which won’t send all the other (apparently accurate) speeds out of adjustment, or should I take them to a professional?
Thank you,
Chris |
rick
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, April 17, 2004 - 12:52 pm: |
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It's probably a cleaning problem: a slight amount of friction or hesitation in the first curtain can let the second catch up with it at 1/1000 second. something in particular to look for is dirt of a film chip in a pair fo gears that are attached to the opening curtain drum.... a single speck of dirt on one tooth can cause a hesitation that will delay the curtain 1/1000 second and then let it go free, leaving 1/500 just slightly fast and other speeds not measurably affected.
I've seen this a number of times in screwmount leicas, which get film chips in a big gear at the bottom of the curtain drum.
rick  = |
Stuart Willis
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, April 29, 2004 - 08:31 pm: |
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Getting 1/1000 second on a horizontal scan fabric focalplane shutter can be a tricky business.
The Exakta Varex models are particularly difficult but sometimes one gets lucky.
Everything has to be just right. I refer to cleaniless, spindle friction, lubrication and of course the correct spindle tensioning and determination of starting position and curtain overlap. As Rick says - a film-chip foreign body in the wrong place (aren't they always?) can be enough to stuff things up.
If you are not familiar and experienced with focalplane shutter work - you might choose to live with the shortfall if 1/500 sec is OK.
Hope this helps ... a bit.
Stuart Willis |
Rafael Chamon
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, January 08, 2005 - 10:59 am: |
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Hello, Chris!
You know that the shutter consists in two courtains, which are driven by means of two separated springs. These springs are tensed when you advance the film. When you press the shutter button the first courtain is released and it opens the picture window. After a while, depending of the shutter speed you have set, the shutter mechanism releases the second courtain and it closes the window.
The reason of your problem could be that at 1/1000 sec the second courtain catches up the first one during their travel, so the film window is darkened. (The reson I do not know, perhaps the lubricant oil of the shutter has become dry, or whatever).
How to fix it: There are two adjust screws to modify the tension of the springs that drive the courtains. These screws are easily reached if you remove the botton plate. By turning these screws you can easily modify the tension of the springs so you will modify the speed of the courtains. So, to avoid that the second courtain catches up the first one you can either speed up the second courtin or slow down the first one.
Procedure: Remove the botton plate (easy and harmless). You will easily identify the two adjust screws, located on the left side of the camera botton. The screw which is located closer to the camera back adjusts the first courtain (open). The screw which is located closer to the camera front adjusts the second courtain (close). A rotation clockwise increases the spring tension. During the adjusts try always not to loose control of the positions of the screws. Eventually note down your movements. You have, either to speed up the second courtain or to slow down the first one.
Try first to speed up the second courtain.
Iincrease the tension of the second courtain in steps of ½ tour and check every time the shutter obstruction at 1/1000sec. Repeat til the obstruction disappears.
If this procedure does not work, return to the initial situation and try to slow down the first courtain in a similar way.
If you can manage to adjust the shutter for 1/1000 sec, it will be also adjusted for the rest of the shutter speeds.
This way I could manage to fix a similar problem as you have, on my K1000 body. (However I do not know if the shutter is well callibrated now, I simply removed the obstruction)
Good luck
Rafael |
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