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Nparsons13
Tinkerer
Username: Nparsons13
Post Number: 16
Registered: 09-2010
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, November 13, 2011 - 05:23 pm: | 
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I recently acquired a Pentax second-model clip-on light meter (rectangular, as opposed to the earlier cylindrical one), for the SV series, and found that the needle sticks, probably because the needle pivot has been knocked out of its bearings. Has anyone on the forum ever disassembled one of these meters? Is it possible to repair? |
Old_school
Tinkerer
Username: Old_school
Post Number: 135
Registered: 04-2011
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, November 14, 2011 - 01:08 pm: |
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N: The wikipedia site http: //en.wikipedia.org/wiki/Galvanometer
Will give a good description of the basic movement, for reference.
I have not opened that particular unit, but they are all very similar inside. You should be able to open & inspect the pivots, & maybe flush with a drop of lighter fluid from a pinch in-between your tweezers. Care needs to used around the hairsprings & coil as they are easy to damage. Inspect with a eye loop for any particles sticking to the magnet. They are easy to remove with a fine needle to remove any iron particles if present. Can practice on a fridge magnet & some iron filings.
Clean the bumpers that the pointer strike against at the extreme ranges. Clean all the contacts too.
Good luck! The Best Mike... |
Steve_roberts
Tinkerer
Username: Steve_roberts
Post Number: 68
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, November 16, 2011 - 03:32 am: |
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When working properly, these meters are surprisingly good in my experience, so it's worth persevering!
Steve |
Nparsons13
Tinkerer
Username: Nparsons13
Post Number: 17
Registered: 09-2010
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, November 19, 2011 - 05:08 pm: |
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Well, I couldn't find anything online on repairing the Pentax clip-on meter, so I dived in. The problem turned out to be that the brass spring plate and screw that clamp the galvanometer in place had come loose, and the plate had fallen inside the galvanometer. Also, the tape with the f-stop scale came loose when I opened the meter, and reattaching and recalibrating it turned out to be the biggest job. But I finally got it done, and now the meter works perfectly.
Since there isn't anything online about how to open one of these clip-on meters or how to recalibrate it after putting it back together, I have posted my notes at https://sites.google.com/site/pentaxmeter/. If anything in it isn't clear, or if anyone wants to add useful information to it, please pass your comments along. |
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