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  1. #1
    Eric Rose's Avatar
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    Ok call me a crank, but I like the older mechanical equipment like Nikon F2's and Canon F1's etc. None of that wizzy stuff for me. And I'm not even going to get into the MF and LF gear I have. All mechanical. Still works when the battery goes dead. Now try that with the new elecronic marvels.

    Anyway I digress, one of the disadvantages of using this old stuff is that they were designed to operate with 1.35v mercury batteries. Something our enviromnent I guess really doesn't need in the landfills. The new replacement batteries are 1.5v. Hence incorrect readings.

    I did some searching on the net and Photo.net and found the MR-9 appliance as well as the Wein battery alternatives. I also found some had used a 675 battery with washers to replace the 625.

    I meandered over to my local Radio Shack with my old Gossen LunaPro and proceeded to try different battery combinations. Tried the 675's and when I hit the battery check it was well short of the required spot. Funny considering they are 1.4v batteries (needs 2). Horsed around with other batteries and finally settled on the 625's at 1.5v each.

    When I did a battery check it was just over the sweet spot. I then compared results once I got home to my Pentax Spotmeter and a Zeiss meter. It was only about 3/4 of a stop high. That's an easy compensation to live with.

    Now to my question. I would rather get inside this little beasty and rework the wheatstone bridge or whatever it uses with new resistor values so it will read accurately with the newer batteries. Does anyone have a repair manual or wiring diagram they can share with me that would allow me to accomplish this?

    The meter is not worth taking it into a repair shop to do something I can do myself.

    Any help would be greatly appreciated. Also does anyone have any first hand experience with these MR-9 adapter thingies? I've heard pros and cons on them.

    Eric
    www.ericrose.com
    yourbaddog.com

    "civility is not a sign of weakness" JFK

    "The Dude abides" - the Dude

  2. #2

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    I'm like you. I LOVE the old stuff. I have an old F2, and FT and an FT2. Guess which one is easiest to get batteries for....

    I feel your pain of course.

    In my experience though, there is little you can do. I tried those nasty Wein cells. They simply DIDN'T work at all. The adapters seem dodgy and I am a bit wary of them.

    You know what seems to work best?

    Those 1.5v batteries. I have an old Pentax Spotmeter that uses a 1.35 and a 9 volt (why, I have no idea....). I finally gave up and used a 1.5V.

    It works perfectly. I used it on some 4x5 Velvia chromes and it came out fine.
    Official Photo.net Villain
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    [FONT=Comic Sans MS]DaVinci never wrote an artist's statement...[/FONT]

  3. #3
    David A. Goldfarb's Avatar
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    On the other hand on my Canon EF, the meter won't read at all with 1.5v cells. I use the Wein zinc-air cells and just always keep spares on hand for when they run out. Best price I've found for them is at bhphoto.com.
    flickr--http://www.flickr.com/photos/davidagoldfarb/
    Photography (not as up to date as the flickr site)--http://www.davidagoldfarb.com/photo
    Academic (Slavic and Comparative Literature)--http://www.davidagoldfarb.com

  4. #4

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    This site has a workaround for Minolta SRT that might be of interest.

    http://www.pcisys.net/~rlsnpjs/minolta/mercury.html

    I only have one camera with this problem and just use the 1.5v or a handheld lightmeter. The in camera meter with the 1.5v doesn't seem that far off but I haven't really checked it that closely as I only use it for close ups with strobes.

  5. #5
    Eric Rose's Avatar
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    </span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (BobF @ Nov 27 2002, 06:53 AM)</td></tr><tr><td id='QUOTE'>This site has a workaround for Minolta SRT that might be of interest.

    http://www.pcisys.net/~rlsnpjs/minolta/mercury.html

    I only have one camera with this problem and just use the 1.5v or a handheld lightmeter. The in camera meter with the 1.5v doesn&#39;t seem that far off but I haven&#39;t really checked it that closely as I only use it for close ups with strobes.</td></tr></table><span id='postcolor'>
    Wow that site is amazing&#33; Thanks. Being an electrical type I will certainly delve into this project&#33;

    Eric
    www.ericrose.com
    yourbaddog.com

    "civility is not a sign of weakness" JFK

    "The Dude abides" - the Dude

  6. #6

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    Adorama sells a kit for the old Gossens. I bought one and it works great. It is basically a plastic cylinder with a metal bottom and some circuitry inside that converts to the right voltage. My Luna Pro is accurate again.

    Gossen Luna PRO S Battery Replacement Kit #4145:

    http://www.adorama.com/catalog.tpl?op=deta...6567&sku=GSLPSB




  7. #7
    Flotsam's Avatar
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    Does that replace two Mercury 625s? I wonder if it could be used in an F Photomic prism.
    That is called grain. It is supposed to be there.
    =Neal W.=

  8. #8

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    The nice thing about mercury batteries is (was) that they have a flat discharge curve- the voltage remains constant almost until the end. Zinc-air and alkaline among others do not do this. The voltage gradually declines throughout their useful life.

    This means that even if you were able to recalibrate (or compensate) your meter for the higher initial voltage, the accuracy will change unpredictably as the battery ages.

    Best bet, if you are using a PX13 or PX625 is to use a MR-9 adapter which is a voltage regulater that works together with an easily obtained 386 watch battery to provide the required constant 1.35v.

    C.R.I.S. Camera Services (http://www.criscam.com/mba.htm) also has other similar adapters for the replacement of PX27 and PX32 batteries.

  9. #9
    dr bob's Avatar
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    Equipment using a bridge circuit and a "match needle" mechanism should work just as accurately with any power source provided the voltages is not extremely high (or low). These circuits employ a null point to operate and only require a source of power. I have a tiny Vivirar meter, which states that it can use either mercury or Ag/Zn type provided the physical size is compatible. My experiments verified this. My old Pentax Spotmeter camera (the one with screw-on lenses) can also use either.

    Truly, dr bob.
    I love the smell of fixer in the morning. It smells like...creativity!
    Truly, dr bob.

  10. #10

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    I bought a few Mercury batteries for my Canon FTb from www.px625.com
    Seems to work just fine.

    Thor Egil

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