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George Welcher
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, January 11, 2006 - 02:56 pm: | 
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I picked up a Spotmatic II in great shape, but the meter is out of whack (technical term). After some superficial cleaning, I inserted a new WienCell 1.35V battery, and tested the meter by desklamp on a sheet of paper. The meter needle jumped way up into the plus section, even set at ASA 100. Setting the shutter speed to 1/1000 at f16 brought the needle back down. This was obviously wrong, but I checked with my Vivitar 45 which gave me a reading of 1/60 at f4, which seemed more likely. Hard to figure how the calibration got so bad.
There had been some corrosion of the contact under the battery compartment from a leaky battery. As I was cleaning this up, I noticed two set screws under the bottom plate, and wondered if these were adjustment screws for the meter.
Does this sound like a calibration issue, or are there likely other causes? Anyone had experience with calibrating meters on these cameras? What's involved?
Thanks |
rick
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, January 11, 2006 - 06:24 pm: |
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i don't think this sounds like a calibration issue, i think you have some damage in the circuit. i don't recall it in detail, but the pentax meter is a balanced circuit which uses power to deflect the needle either up or down from the center (if you remove the battery, you should find the needle more or less centered in the meter). if it goes way to the top i think maybe you have a bad connection in the downward side of the circuit. |
Stuart Willis
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, January 12, 2006 - 04:27 am: |
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Here's a (likely) possibility.
The Spotmatic uses two cds cells which are wired in parallel.
If one of the cells goes short circuit or open circuit - you get two opposite major metering flaws.
It is a fact that the Spotmatic will function perfectly well with just one cell - so all you may need to do i isolate the faulty one and leave the good one in situ. Any high impedance digital multimeter will reveal which is the faulty cell.
Hope this helps
Stuart |
George Welcher
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, January 12, 2006 - 09:35 am: |
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Thank you both for the tips. I'll see if I can find a manual on eBay before I start tinkering. |
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