PX625 Gossen Luna Pro Current Draw Question

Discussion in 'Camera Building, Repairs & Modification' started by Grif, Nov 16, 2010.

  1. Grif

    Grif Member

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    After doing some searching on two or three different sites, I'm about half scared to ask this question,,, seems to be a bit religious/political for some odd reason, but here goes.

    What is the current draw of a normal Gossen Luna Pro light meter?

    Any other light meters (analog) current draw you know of that used mercury cells?

    What I found, looking at the various adaptors, was a feeling that around 5ma was about maximum that the various diode silver oxide replacement adaptors would tolerate. I'm looking at the MAX 6037 in surface mount as an option.

    I wish I could find my old battery design manual from GE

    Opinions?
     
  2. MartinP

    MartinP Member

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    I had (until an unfortunate accident involving a lake) a Lunasix 3 for more than twenty years and, after weighing up all the alternatives and their reliability etc. etc. I ended up buying the relevant adapter from Gossen. End of problem and zero hassle. I'd still suggest their own adapter as it's cheaper in fiddle-time, reliability and money than all the alternatives I could find.
     
  3. AgX

    AgX Member

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  4. DWThomas

    DWThomas Subscriber

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    I'd be willing to bet the draw is well under a milliamp, maybe down toward 100 microamps. The meter movements in those appeared to be rather delicate, as in highly sensitive to get those moonlight readings. I had one in the 1960s and the meter movement itself appeared to have opened up after a half dozen years. I sent it off and spent the cost of a lesser meter to get it repaired. When the bugger then died about two months after the repair warranty ran out, I gave up on it.
     
  5. Grif

    Grif Member

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    Appreciate the leads and comments, I'd seen the pdf of the adapter using a schottky diode to drop a silver cell, I think I'll pick up a couple of the MAX6037's to play with. My feeling was also that the LunaPro was down at or below a ma. I've got two or three (more if you ask the wife) main hobbies,,, electronics is right up there, so also enjoy the DIY side of the electrical parts of photography. I've got two or three light meters, a flash meter, and seems like another device that depend on the mercury cell as a reference, not counting another odd project in the wings that needs a solid reference voltage. I always wanted a Luna Pro as a younger person, now I've got one running very well,,, but still on mercury cells. Nikon has been internally modified for silver oxide, I can't imagine the Luna Pro doesn't have a lot more room inside than the Ftn head.