FM Battery Issue

Discussion in 'Nikon' started by exaktamoment, Oct 5, 2017.

  1. There is a little bump in the bottom of the battery holder (that goes through the hole in the paper).

    That, and the shape of the battery itself, where the button part sticks out just enough,
    should keep it from shorting.

    http://data.energizer.com/pdfs/a76.pdf

    or the one I usually put in the FM:

    http://data.energizer.com/pdfs/2l76.pdf

    The design of the FM is that if the meter works, it is correct.
    When the battery voltage is too low, it turns off.
    (With no warning.)

    The fast drop-off of the 2L76 doesn't help, though.
     
  2. Hey Y'all. I found an elderly 2L76 in the package, in a drawer. I tested it for voltage and it read 3.25 volts, so I put it in the FM and by goodness it worked. I set it down and walked away to do something else, came back a half hour later and it didn't work. BUT. I checked the voltage again and it was down to 1.2 volts. I'm putting that down to age of the battery. I'll replace it tomorrow and try again, but i think the 2L76 is the answer. Of course, if it pulls down again in an hour or so (an hour with the metering system shut off) then I'm going to have to look toward a short in the system.

    Lou
     
  3. FWIW, I was a bit skeptical of the short circuit comments earlier, but I've been fighting a bit with an FM lately.

    I had put two Duracell silver LR44 equivalents in it, and when I went to play with it the other evening I found both batteries dead and the lower one swelled(making me think it had indeed shorted). I'm going to try the suggested paper ring trick also in this camera, although I have a BIG stash of these Duracell batteries and they have served me well in F2s, F3s, and a few other cameras.
     
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  4. Vincent Peri

    Vincent Peri Metairie, LA

    Ben, is that the FM I recently sold to you? If it is, send it back for a full refund.
     
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  5. Sorry, I meant FE. The FM you sold me is working perfectly.
     
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  6. I have an FE that works perfectly and it uses the same battery setup that the FM uses. So, besides my voltmeter, this is my test bed for batteries. So. I went to the battery store and bought a brand new 2L76. That's a single 3v battery that is the other proper one to insert in the camera. And it worked. It tested at 3.26v and initially, it worked. I had LEDs as soon as I turned on the camera, I cocked the shutter and fired it and I still had LEDs but I cocked and fired again and the LEDs went out. I pulled the battery and tested and the battery showed 2.78v. So riddle me this, Batman - in a camera that's Fully Mechanical, in which the only thing that the battery is used for is the light metering system, how is it that battery drain seem co-incident with the shutter being fred?

    What is there in an FM than can short and drain the battery?
     
  7. I think you can leave the meter on for a while then the battery would be dead. When the battery read 2.78V without load that's dead. And a fresh battery is dead in the matter of minutes the short is severe.
     
    Last edited: Oct 15, 2017
  8. The manual says "a few days" although I've never tested it.

    I don't know EXACTLY how the metering circuit in the FM is laid out, but any time the meter is on it will draw power since it has to illuminate the LEDs. With a CdS/galvanometer meter as on all the F metering prisms and the most common F2 prisms(DP-1, DP-11) putting a lens/body cap on will have much the same effect as turning the meter off. In fact, the very first F Photomic meter just had a flap("flag") that was raised and lowered to cover and uncover the metering cell.
     
  9. If there is no short and you leave the meter on the battery would be dead in a few days. But as the OP said it's dead in the matter of minutes then there is a bad short. The fact that with the old batteries the OP could get it to work by not screwing the cap in too tight I think the problem can be fixed relatively easy as the problem is only where the battery compartment. Removing the baseplate may reveal the problem.
     
  10. I talked to a friend of mine and he suggests I would probably be better off to just get another FE or FM - it would cost more than a substitute camera to ship and repair the wonky FM. I'll do that, I suppose, but I'll keep the FM in hand - to see if I can fix it myself.
     
  11. I think you should try to fix it yourself. Remove the base plate and check the battery compartment. It is possibly when the cap is screwed in tight it pushes the battery compartment inward a bit and the bottom of the compartment may hit something.
     
  12. BeBu, I probably will - I'm certain I'm not going to send it out to repair. As I said, it would cost more to ship and fix and ship back than to just get another camera. That said, I AM curious as to what is wrong with this beast and I think it would be cool to figure it out for myself.
     

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