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Olympus OM1n battery

Discussion in 'Classic Models & Marques' started by Ian51, Dec 22, 2015.

  1. Ian51

    Ian51 New Member

    Hey all

    I have recently purchased my as new OM1n and although the lens that came with it is a bit rough the body is as described. Mint+++

    So it came with a PX625 battery and I switched on the meter which sprung to life. The battery is a 1.5v so I am aware that I need the CRIS convertor to use a 1.3v silver battery for correct exposure. The needle was jittery and swung violently on occasions so rather than delve into the depths and start checking wiring and terminal etc. I thought I would try a commonly substituted hearing aid battery just to rule out the possibly dodgy battery that might have come with the camera.

    So heres the thing. I put a 1.5v hearing aid battery in and once again the meter swung into life and seemed steady. That was enough for me to go ahead and order the proper battery convertor from ebay. I turned off the meter and the meter was still metering and reacting to both aperture and speed settings. I took the battery out and it is still metering and reacting to changes in settings.

    Does anyone know if a charge is held in the meter for a while. I have left it half an hour and it is still metering. I was expecting the meter to immediately switch off but it has not done. It did switch on and off with the first battery so how comes it is still metering without a battery.

    Imagine if I had a fully functioning meter OM1n which didn't need batteries. How cool but also how impossible.:)

    Any ideas folks??
  2. Ian51

    Ian51 New Member

    No problems all sorted false alarm :D
  3. Trannifan

    Trannifan Well-Known Member

    The exposure meter circuit seems to be a weak point in the OM1n. Years ago I inherited an OM1n from my father. One day the meter just packed up and a new battery didn't bring any life to it. Down at the local camera shop the reaction was, "Ah yes, we know about this problem......."

  4. Ian51

    Ian51 New Member

    Hi Lynn

    Thank you for the reply. For some strange reason it seems to have rectified itself and the meter is working fine. I doesn't explain how a meter could work without a battery but it works so I can go out and take some pictures.

  5. jchrisc

    jchrisc Well-Known Member

    I used an OM1n for a long time but memory fades. I'm pretty sure however that it used a 1.3v Mercury battery and it was the banning of Mercury that brought the need for adapters. When the battery ran down, the only thing that stopped working was the meter. It's difficult to understand how it would meter without a battery. In its later life I used the camera a lot with a hand-held meter.
  6. Trannifan

    Trannifan Well-Known Member

    According to the OM-1 instruction manual, the required battery is a PX625 1.35V mercury battery. "Alkaline batteries (LR44, A76 etc.) may not be used."

  7. Ian51

    Ian51 New Member

    Hi there Lynn

    Thank you for the reply. I have ordered a small battery adaptor which allows the new silver 1.5v batteries to be used it adapts the size to the PX625 and also reduces the voltage down to 1.35v so I think I've sorted it. I just need to win the lottery so I can buy a 50mm f1.2 lens and a 24mm f2.8 tee hee :)

  8. Olyfix

    Olyfix New Member

    I realize this is an old post, but for informational purposes I reply.

    On the OM-1 and OM-1n cameras, it is possible to mechanically position the meter so that, even "off" or without power, the needle deflects off the lower stop. In other words, it may appear that you have set the needle within the bracket for an accurate exposure (using the "B" or an extremely low shutter speed setting along with a wide open or near wide open lens aperture), but you will note that the needle does not react to changes in light. (The very, very earliest OM-1 cameras were built with circuitry to deflect the needle in this event (presuming the camera has power), but this was deemed unnecessary and discontinued quite early on.)

    The trick is to first check voltage on your battery. If it's "good" (1.35 volts or so), install it and, with the camera set to a lower speed and open aperture in bright light, watch as you switch the camera on and off. The needle should deflect. If it does not, you likely have a problem. Depending on the internal version and other factors, the battery lead (brown) and it's connection to the battery terminal may have corroded (quite a typical malady), or the meter's ground may be faulty. If the meter is "jumpy", it could be poor ground, a pinched or broken battery lead (brown wire) or a pinched or broken galvanometer wire (blue). After that, the causes become more and more unusual, and the skill of an experienced Olympus repair tech are in order.
  9. John Farrell

    John Farrell Well-Known Member

    A friend had an OM-1n, on which the insulation between the battery contact and its securing screw had broken down, grounding the battery. I replaced the metal screw with a nylon one, after recutting the the screw thread with an M2.3 x .4 die.
  10. Olyfix

    Olyfix New Member

    Ah, yes! At first, Olympus used a 1.7mm steel screw with a plastic insulator to hold the battery terminal in place, but switched to a 2mm hard plastic screw. Precisely when they switched over I don't recall, but the plastic screws began to break in droves! The plastic screws are no longer available (of course!), but fortunately, you can find slightly larger nylon screws in english dimension that do a fabulous job. The hole tapped in the body effectively cuts it's own threads on the nylon screw, and once screwed snugly in place, you simply slice off the end sticking up into the film take-up chamber with a small blade. Presto, fixed!
  11. Conmai

    Conmai New Member


    My googling led me to this thread, I hope someone is out there :)!!. So I have been attempting to troubleshoot a faulty meter on my OM1 the below is what I have done

    Initial inspection I found that the brown battery wire had come away from the battery terminal tab and the wire was also corroded.

    removed steel screw with a plastic washer from the round balck battery holder on the bottom of the camera, also removed the other retaining screw and the battery holder and terminal tab
    Removed the cameras top cover
    followed my procedure for uncoupling the mirror housing from the main camera chassis
    unsoldered the end of the brown wire still attached to the circuit board (top left on camera)
    removed the brown wire completely and threaded a new one through
    solder the new wire to both the circuit board and the batter terminal tab
    refitted the battery holder, terminal tab, and two screws
    fixed back together the mirror housing section to the main camera chassis
    tested all shutter speed settings and all okay
    set asa to 1600, B speed setting and aperture to f8.0, needle was one stop over centre so adjusted galvonmeter (loosened locking screw and adjusted eccentric slightly, all good as the needle was nice and centre
    Adjusted both shutter speed settings and aperture settings and could see that the galvanometer turned as expected, also the needle was deflecting slighty to changes in settings

    So now I start to get confused!

    I'm thinking at this point, a good job done thus far, new battery wire, half decent soldering and adjusted the zero for the needle

    tested spare 625 battery with multimeter, red contact on + side of battery and black contact on bottom of battery, reading was 1.25v
    Inserted battery into battery holder
    used multimeter, again red contact touching the + side of the battery (no bottom cover on at this point) and black multimeter contact on the battery wire\solder on circuit board on top of camera, reading was 1.21v
    Closed the meter switch on circuit board on top of camera and still with the red multimeter contact on the + side of the battery I put the black contact on the CDS red wire solder, it read 1.21v, I also then put the black contact on the blue solder, and the pinkish wire solder on the circuit board and still had a reading of 1.21v
    Lastly I placed the black contact on the Galavonmeter housing and blue wire and again 1.21v
    However with the battery still in and no bottom cover on the needle does not move at all, no response to light in any shape or form, CDS cells covered or uncovered

    If I take the battery out I can set zero, move the shutter speed and aperture and the needle moves appropriatly, interestingly it does the exact same with the battery in, which suggests the meter is not responding to the juice getting to it?

    In my simple head the multimeter is showing me that with the meter switch closed juice is getting to all the right places but I see no deflection of the needle, although mechanically it all moves okay....I think

    When I see suggestions on test ground to Galvanometer what is the exact process to do this as I'm wondering if my grounding is correct, also my electrical understanding is emabarrasingly poor :(

    I may have got myself very confused here or maybe someone can point me in the error of my ways in my summary above but to all accounts it does not seem thata the meter works correctly with a battery in

    A bit of a ramble but any thoughts suggestions or other things I can check greatly appreciated!

    Kind regards
  12. nimbus

    nimbus Well-Known Member

    The battery voltage for these cameras is 1.35v when fresh. The original cell was a now banned Mercury type, I am wondering whether this is due to the battery you are using. There are converters to allow the use of a different type of cell in these cameras, allowing the correct voltage to be applied to the systems. That might be the next avenue to explore.
  13. Conmai

    Conmai New Member


    Thanks for the reply, I did wonder that but have tried the same battery in another OM1 and it works okay :(
  14. PeteRob

    PeteRob Well-Known Member

    If it all works independently but not when assembled then indeed it sounds like a broken connection. I have a digital vernier scale that works perfectly until I close the battery door and this is just a plastic slide that holds the button cell in place. There is no conceivable reason why or how the circuit can break. The button cell sits on a sprung terminal and fits tightly around its circumference, all the cover does is stop it falling out.
  15. John King

    John King In the Stop Bath

    It is years since I had any version of an Olympus but yes with my two OM1n bodies they both would show a needle deflection if the battery was removed. It wasn't by any measure accurate but it did move significantly, and the brighter the subject the more movement as you would expect..

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