error404
Newbie
Is anyone aware of a diagram that shows how the contacts in a Contax IIIa meter connect the selenium cell to the meter housing? So far, I've come across:
- Kiev Survival site (but Kiev meters seem to use different connectors)
- Zeisscamera.com site (which shows the connector clips attaching to the selenium cell, but not exactly how they connect to the meter :/
Grytpype
Well-known
I've photoed the parts from a scrap camera.
Both the contact tabs visible from above are the 'earth' connection. They are clamped to the body, the left by the front-flap screws, the right by thr meter cover (though the one in my photo was short, and I would not have needed to remove the meter cover).
The cell and its lens slide out upwards. There are two metallised strips on the front of the cell that contact the earth tabs, and the other connection is made between the metallised back of the cell, and a spring plate attached to the body. It all falls apart so you can polish the connections.
Good luck!
Both the contact tabs visible from above are the 'earth' connection. They are clamped to the body, the left by the front-flap screws, the right by thr meter cover (though the one in my photo was short, and I would not have needed to remove the meter cover).
The cell and its lens slide out upwards. There are two metallised strips on the front of the cell that contact the earth tabs, and the other connection is made between the metallised back of the cell, and a spring plate attached to the body. It all falls apart so you can polish the connections.
Good luck!
Highway 61
Revisited
I have once replaced the dead selenium cell of a Contax IIIa with a selenium cell taken off a Kiev 4.
You have to make the Soviet cell a bit shorter, and also thinner by removing some material off the metallised back of the cell with a dremel so that it fits in the Contax shell. Also, the ground and positive connectors are of a different design and you have to use some bits of wire and your soldering iron to connect it the good way.
But, all in all it's not that difficult. Once done, the Contax IIIa meter works perfect, with a good calibration. The Kiev cell readouts are very similar to the original Gossen cell, which is not surprising for rectangle selenium cells of a similar size.
You have to make the Soviet cell a bit shorter, and also thinner by removing some material off the metallised back of the cell with a dremel so that it fits in the Contax shell. Also, the ground and positive connectors are of a different design and you have to use some bits of wire and your soldering iron to connect it the good way.
But, all in all it's not that difficult. Once done, the Contax IIIa meter works perfect, with a good calibration. The Kiev cell readouts are very similar to the original Gossen cell, which is not surprising for rectangle selenium cells of a similar size.
David Hughes
David Hughes
Polishing or cleaning terminals is the answer to a lot of faults with low voltage devices as tarnish etc can create enough resistance to stop things working.
A long, long time ago when TV's and radios ran off valves the techs used to remove the valves and clean the male contacts with brass wire brushes (the sort of brush we used to clean our blue suede shoes). It took seconds but as the device was left with them for a day or two their charges were a lot higher. It was still cheaper than two matched KT66's...
Sometimes unplugging and then reinserting components would do the trick as the friction did a bit of cleaning and then it would be reported as "no fault found" and a few weeks later it would start again and the customers would come back. The moral is to do the job properly in the first place.
Regards, David
A long, long time ago when TV's and radios ran off valves the techs used to remove the valves and clean the male contacts with brass wire brushes (the sort of brush we used to clean our blue suede shoes). It took seconds but as the device was left with them for a day or two their charges were a lot higher. It was still cheaper than two matched KT66's...
Sometimes unplugging and then reinserting components would do the trick as the friction did a bit of cleaning and then it would be reported as "no fault found" and a few weeks later it would start again and the customers would come back. The moral is to do the job properly in the first place.
Regards, David
error404
Newbie
Success!
Success!
Thank you all for your comments, the pictures were especially helpful. I was successful in getting the meter to work again -- the problem actually turned out to be the connection between the ISO adjustment knob and the meter.
I did discover that the meter on my camera has definitely been overhauled at some point: the selenium cell is stamped with a post-production 1968 date, and has soldered connections (front and back). The earth clips actually don't seem to be doing any real work at all, in my case.
Success!
Thank you all for your comments, the pictures were especially helpful. I was successful in getting the meter to work again -- the problem actually turned out to be the connection between the ISO adjustment knob and the meter.
I did discover that the meter on my camera has definitely been overhauled at some point: the selenium cell is stamped with a post-production 1968 date, and has soldered connections (front and back). The earth clips actually don't seem to be doing any real work at all, in my case.
Attachments
Grytpype
Well-known
Interesting! Looks like a very sensible mod. for improved reliability. I wonder if it was Zeiss Ikon's idea, or a repair shop's. Has anyone stripped the meter on a late model IIIa, and did it still show the connections as in my pictures?
Highway 61
Revisited
For some obscure reasons almost all the Contax IIIa selenium cells had a prematurate death while most of the exact same cells installed in the Zeiss Ikon Ikophot handheld meters manufactured at the same time are still working nowadays, provided that the meter was kept in the dark when not at use (which was easy thanks to its nice foldable leather case). The IIIa meter cover is not light tight enough but that doesn't explain it all. The camera shell might have behaved as a permanent and unwanted current drain source, slowly but surely exhausting the cell.