Battery for Pentac Spotmatic

Discussion in '35mm Cameras' started by jwr4, Jun 10, 2004.

  1. jwr4

    jwr4 Guest

    I've had a great Pentax Spotmatic outfit since 1973. The first couple
    mercury batteries I used lasted somewhere around 10 years each. Then
    mercury batteries were banned in the U.S. and I had to find a
    replacement which was zinc air cell battery.

    This lasted a year of so. Last fall I experimented with a 1.4 volt air
    cell hearing aid battet because I could buy them at Walmart and didn't
    have to send away for it.

    Lasted only a couple months. They came in a package of 4, so I put in a
    new battery. It didn't work.

    Is there anything equal to the original mercury batteries when it comes
    to battery life?
    jwr4, Jun 10, 2004
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  2. jwr4

    Matt Clara Guest
    Matt Clara, Jun 10, 2004
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  3. jwr4

    Nick Zentena Guest

    Just buy a silver battery. Voltage is wrong but the camera doesn't care.

    Nick Zentena, Jun 10, 2004
  4. jwr4

    Alan Browne Guest

    .... metering error?
    Alan Browne, Jun 10, 2004
  5. jwr4

    Mike Guest

    The bridge circuit will handle the voltage of a 1.5 volt silver battery
    without error. A little silver watch battery and a rubber O ring to keep
    the battery centered is all that is needed.
    Some stores sell the silver oxide battery in the same plastic ring that was
    found around an RM400 battery. In fact you can pop the RM400 out of the ring
    and insert a silver oxide watch battery.
    Mike, Jun 10, 2004
  6. jwr4

    Minolta Man Guest

    I don't recall the exact number but a 1.55v silver oxide cell with
    rubber "O" ring will work fine..

    The spotmatic uses a bridge circuit so the extra 0.2v won't matter..

    Colyn Goodson

    Camera manuals and mercury battery fix

    Weston Ranger 9 battery fix
    Minolta Man, Jun 10, 2004
  7. jwr4

    Mike Guest

    I am using an S936SVinni Slivercell, it is a watch battery
    Mike, Jun 11, 2004
  8. jwr4

    Guest Guest

    a écrit :
    Use 1.5V silver battery:
    Guest, Jun 11, 2004
  9. jwr4

    Alan Browne Guest


    Alan Browne, Jun 11, 2004
  10. keep

    Umm, maybe. Not likely though. You may end up with up to 1/2 stop error,
    unless the bridge is recalibrated. Or you can go to CRIS camera (they're on
    the web) and buy an adapter that drops the 1.5V of the silver battery to the
    1.35 of the mercury, and adapts it to the recess.

    Mike Lipphardt, Jun 11, 2004
  11. jwr4

    Nick Zentena Guest

    Have you tried it? One shop is selling an "adaptor". All the adaptor is
    a rubber ring that fills the gap between the smaller battery and the bigger old
    battery. Now if you can find a 400S or a 387S [think it's a 387] then they
    should fit just fine. Considering the newest Spotmatic is around 30 years
    old any error could easily be something other then the battery. I know when
    I check my almost 40 year old Spotmatic with a silver battery the meter
    matches very well with newer cameras.

    Nick Zentena, Jun 11, 2004
  12. jwr4

    Minolta Man Guest

    I've tested the spotmatic with 1.55v silver cell without re-cal and
    the exposures are right on..

    The bridge circuit is not dependant on exact voltage, therefore a
    difference of 0.2v will not make a difference..

    However a series circuit such as the Minolta SRT series cameras will
    require re-cal or the addition of a schottky diode in line with the
    battery wire to reduce voltage to the required 1.35v..

    Colyn Goodson

    Camera manuals and mercury battery fix

    Weston Ranger 9 battery fix
    Minolta Man, Jun 11, 2004
  13. jwr4

    Mike Guest

    While an error is possible, I have been using the silver watch battery and a
    rubber O ring without a problem in the Spotmatic cameras for several years.
    In other cameras such as the SRT's, Konica's
    I install a diode to drop the voltage which eliminates meter errors..
    Mike, Jun 11, 2004
  14. jwr4

    Guest Guest

    Recalibration not necessary for bridge; here wiring and circuit for
    Spomatic family: Circuit and Adjustment, Spotmatic F/, Shutter Adjust, ES and ESII/
    Guest, Jun 11, 2004
  15. I have. The CRIS adapter is not a rubber ring. It is a shell that a silver
    batter fits into, and which drops the voltage to the proper level. I've
    used it in my older Mamiyas that take mercury, and which diplayed metering
    errors with silver.

    Mike Lipphardt, Jun 11, 2004
  16. jwr4

    Jeremy Guest

    I began using the 387S batteries several years ago, and they work fine. The
    rubber spacer ring is already attached, and they fit perfectly. They last
    about a year.

    You can order them at any Radio Shack store. They are not stock items, but
    Radio Shack has an excellent parts service. You pay at the store and the
    batteries are mailed to you for delivery in 3 or 4 days. Get a couple of

    Their Stock number is CNB-387S and their RSU Number is 11608452.

    You install the battery with the rubber spacer ring facing OUT, i.e., away
    from the camera body.

    If you have a Spotmatic-F, that takes a Varta V625U battery, which is a
    stock item at Radio Shack Stores.

    I've never noticed any difference between the performance of the old mercury
    PX 400S and the current 387S batteries. The voltage drop in the mercury
    batteries was much flatter than today's equivalent, but I just replace the
    387S every 12 months, without waiting for it to die, and it works out fine.
    Jeremy, Jun 17, 2004
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