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Rick_oleson (Rick_oleson)
Legend
Username: Rick_oleson
Post Number: 1384
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, April 07, 2025 - 12:38 pm: | 
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I have two Nikons from the mid 70s, an F2A and a Nikkormat FT2. Both are in good shape and the meters work but both are reading about a stop high (resulting in underexposure). Does this seem odd? I’d have thought they’d be more likely to lose sensitivity with age than to gain it. |
Robert Feldman (Rafeldman)
Apprentice
Username: Rafeldman
Post Number: 12
Registered: 11-2021
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, April 14, 2025 - 10:13 am: |
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Rick,
I do not have a definite answer for you, but have some suggestions.
First, one online post I saw states that you will get a 4-stop underexposure if one of the two CdS cells has failed.
Second, CdS cell circuits can be configured to either increase voltage with more light or decrease voltage with more light. The attached diagram from http://www.neufeld.newton.ks.us/electronics/?p=135 shows the two circuit variants. If a failed cell (failed to open?) causes underexposure, then the Nikon might have a circuit that decreases voltage with increasing light.
You should measure the voltages at the meter coil and resistances at both CdS cells to see what the problem might be. I assume that you are using the correct batteries.
Bob
Pre-2013 Username: r_a_feldman
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Rick_oleson (Rick_oleson)
Legend
Username: Rick_oleson
Post Number: 1385
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, April 14, 2025 - 10:17 am: |
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Thanks! I’ll look into that. Yes, I’m using fresh correct batteries in both. |
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