Batteries question

Discussion in '35mm Cameras and Accessories' started by Steve Mack, Sep 18, 2011.

  1. Steve Mack

    Steve Mack Member

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    I own a Nikkormat FTn, which works just fine except for the light meter. I removed the cell I was using because I assumed, probably correctly, that the voltage was incorrect, and the light meter kept wanting to underexpose things by about 2-3 stops. If I put a cell from Wein batteries in it, one with correct voltage, what are my chances of having the meter work correctly? I do understand that the camera is old(er), and may not have an accurate meter in the first place, so I don't have very high hopes, not unless I spring for a CLA on the meter. I am able to check it with a hand-held meter, so I won't need to guess at the accuracy of the reading.

    Thanks to all who reply.

    With best regards,

    Stephen
     
  2. Ralph Javins

    Ralph Javins Member

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    Good morning, Steve Mack;

    Yes, using a simple Alkaline Type 625A or similar battery in your Nikon F series camera will normally give you a light meter reading that is about 1 & 1/2 or 2 stops off. The normal voltage for a Mercury Cell such as the PX-625 was about 1.35 VDC. A Wien Cell will also give you right at about 1.35 VDC, and it will work properly with your early light meter, but the life may not be as long as you might like. While they are available for use with hearing aids, you might also need to buy them occasionally.

    Another way to consider is with a Silver-Oxide Cell such as the Type 386S which does have a voltage rating of 1.50 VDC, but you can put it into a battery adapter for this purpose such as the C. R. I. S. Type MR-9 Battery Adapter (see the URL of www.criscam.com) which will drop the voltage for the light meter down to right about 1.35 VDC and restore your normal light meter operation. Also, the Silver-Oxide Cell does have a very stable voltage level as the battery is used, so with the MR-9 Adapter, it does simulate the operating characteristics of the original PX-625 Mercury Battery very well, and it gives you consistent light meter operation over the life of the battery. When the Silver Oxide Battery reaches the end of its useful life, you will know it; the voltage does drop very rapidly at the end, and it does so without any real warning that it is going to do this. Have a spare battery on hand for replacement after about a year of use or so.
     
  3. Bob-D659

    Bob-D659 Member

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    Or head off to Costco and buy a card of thirty blue tab hearing aid batteries, approx $12. They will last you a long time, at the fraction of the cost of Wein cells.
     
  4. MattKing

    MattKing Subscriber

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    This is correct, with one qualification. You may need an adapter or some other work-around to deal with the fact that the hearing-aid batteries are a different size then the original mercury cells.

    There are special purpose adapters available that you insert the hearing aid batteries into - size 375 is common.

    In some cases a rubber o-ring will do the job.
     
  5. Rol_Lei Nut

    Rol_Lei Nut Member

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    +1 for using a C.R.I.S.-type adapter.
    For adapting smaller hearing aid batteries, you could try using a wadded-up ball of alu foil to make them fit.

    Despite what some nay-sayers say (who really, really need to read "Zen and the art of motorcycle maintainance"), this is an easy and RELIABLE solution.

    That said, there is probably an even chance that your meter may not be working perfectly: CdS cells can weaken or die and variable resistors get dirty/wear out.
     
  6. Rick A

    Rick A Subscriber

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    I use the Wein cells in my OM-1's and my meters are spot on. I average 2.5-3 years per battery since they only power a meter and get modest usage. It works out fairly cheaply for me.
     
  7. Pumalite

    Pumalite Subscriber

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    I use Air Zinc with a metal ring around (you can get it from the right size spring).
     
  8. Uncle Bill

    Uncle Bill Subscriber

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    How are the CRIS adapters for FTN Meter heads? I picked up a minty Nikon F recently, the speeds are spot on but the on board meter needs batteries.
     
  9. CGW

    CGW Member

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    A single CRIS adapter is OK but two stacked for the FTn finder might be too much. Check how much thread there is on the finder's battery cap. I have a near mint black F Photomic FTn and a small stash of Varta merc cells but rarely use the old beast.
     
  10. Rol_Lei Nut

    Rol_Lei Nut Member

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    I use 2 C.R.I.S. adapters stacked up, both in a Photomic FTn (2 samples) and in a Gossen Lunasix 3 meter: they work perfectly.
    (Why shouldn't they?)
     
  11. Uncle Bill

    Uncle Bill Subscriber

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    That's what I want to hear, thanks!