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Kjb
Tinkerer
Username: Kjb
Post Number: 1
Registered: 09-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, September 21, 2006 - 08:03 pm: | 
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I've got a Nikon FG and the light meter is always showing overexposure. Not sure the problem, any suggestions would be helpful. |
Ethostech
Tinkerer
Username: Ethostech
Post Number: 11
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, September 24, 2006 - 01:42 am: |
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There is an endemic problem with the Nikon FG in that its ceramic based ASA stepped potentiometer is quite delicate. Replacing such would probably fix your exposure errors but finding a replacement component could be a real hassle. Depending upon the crack in the ceramic you may find that you overcome your problem by setting a notch or two higher ASA. This woud be the easy approach. Give it a try. |
Kjb
Tinkerer
Username: Kjb
Post Number: 2
Registered: 09-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, September 26, 2006 - 06:36 pm: |
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Which part exactly is the ceramic based ASA stepped potentiometer? Even setting the asa up to 3200 doesn't have any effect |
Ethostech
Tinkerer
Username: Ethostech
Post Number: 12
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, September 27, 2006 - 04:55 am: |
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That's surprising - unless the ceramic is very damaged indeed OR unless the gold-plated wiper arms are bent, distorted or otherwise not making proper contact.
The ASA ceramic disc-track can be found under the ASA Dial.
You could see it by removing the ASA dial - without removing the camera top-plate ... but to check it out with a multimeter and to attend to possible wiper mistracking you would have to remove the camera top-plate.
That adjusting the ASA has no effect upon your exposure readings pretty much confirms that the trouble-spot is indeed at that variable resistor. |
Ethostech
Tinkerer
Username: Ethostech
Post Number: 13
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, September 27, 2006 - 05:12 am: |
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Here's a picture of the culprit component.
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Kjb
Tinkerer
Username: Kjb
Post Number: 3
Registered: 09-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, September 30, 2006 - 06:02 am: |
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I've traded out the disc track with three others from my parts stock without any affect. The wiper arms look fine. hmmmm |
Kjb
Tinkerer
Username: Kjb
Post Number: 4
Registered: 09-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, September 30, 2006 - 02:34 pm: |
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Here is another interesting bit of information, the camera functions in P and in A, not the light meter but the camera |
Ethostech
Tinkerer
Username: Ethostech
Post Number: 17
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, October 01, 2006 - 04:40 pm: |
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Did you thoughly clean the wiper-arm tracks?
Did you conduct a post-mortem on the removed resistor?
I did so on mine when adjusting the ASA didn't have any effect.
You can use a high-meg digital multimeter to measure the resistance changes at each little segment. It only takes one bridge to be low ohms or open circuit to stuff up the entire facility.
Unlikely as it may sound, Murphy's Law is ubiquitous and given the propensity of this component to malfunction it could be that your replacement parts stock wasn't too flash ??? If the resistor is sound; the wipers stroking properly and the wire soldered joints good, the meter just has to see the input variation.
With a fresh new battery in situ have you checked the voltage output at the resistor - and for variation of such as you change the wiper position in small stages ? |
