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  1. #31
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    Quote Originally Posted by Chris Douglas View Post
    I apologize to the web master for waisting space here. I think this is a valuable service you provide, but not one of the 26 responses addressed my question. I suppose the only people who know how to calibrate an OM1n are the professionals who market their skills at a price.
    Why ignore 26 responses of useful information.

    My personal (amateur) recommendation is to use a zinc cell.

    If you want what a "preofessional who markets thier skill at a price" take heed of the recommendation above for a Shottky.
    Quote from Chamtech photo services website:
    BTW, my OM-1/1N (Pen FT, 35RC, 35RD, 35SP etc.) overhaul builds equivalent MR9 schotkey diode into the meter circuit.
    If that is not enough I'd suggest trying that micro 1.3V regulator, TPS79913DDCR, as it cost only about a buck.

    If you want to tread new ground and re-calibrate the resistors yourself, here is the OM-1 meter schematic. Resistors R1 and R4 control the LOW end and resistors R2 and R3 control the BRIGHT end of the response.

  2. #32

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    So when adjusting a meter, what exactly are the lows n highs you are adjusting to? Is it total dark vs blinding white?

    I've never had any luck with those adjustments n would rather live with the inconsistancies by compensating my exposures using film development n printing standardisation, I get more conssitnat results that way regardless of waht batteries I am using.

    .
    Anyone can make a Digital print, but only a photographer can make a photograph.

  3. #33
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    Here is the adjustment procedure from the OM1 manual:

    BV = Brightness Value (EV?)
    S.S = Shutter speed
    MS 5014 = 50mm 1.4 lens
    "...it returns to the state of the order (1)" = go back to (1) and to through the sequence again


  4. #34

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    Thanks for the tables. I'm sure that will a great help to anyone calibrating the camera.

    Aren't those resistors pots?
    Anyone can make a Digital print, but only a photographer can make a photograph.

  5. #35
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    Quote Originally Posted by paul ron View Post
    Thanks for the tables. I'm sure that will a great help to anyone calibrating the camera.

    Aren't those resistors pots?
    All are fixed resistors. From the blurry pictures I have seen, it looks like they may be 2% (red tolerance band), thus, when tweaking resistor values one can follow the E 48 Series of values.

  6. #36

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    Eureka

    IC,

    Thank you for the procedure, it will be fun to experiment and see how difficult calibration is. I suspect the four resistors are "selected" values that were chosen for each particular camera per a factory procedure. Hopefully there is no difference between the procedure for the OM1, and the OM1n. Thanks again.

  7. #37

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    Just a sugestion to make fine adjustments easy... temporarily wire in a pots and make your adjustments. Then after all is done, measure the pots then use fixed resistors in their place.

    Substituting as you go will make it almost imposable to get anything right plus you'll need a full compliment of resistors to solder in n out each time you need to bring her in. Heat frying your wires n a the mess of solder will just make your life miserable even if you are just tacking em in.

    .
    Anyone can make a Digital print, but only a photographer can make a photograph.

  8. #38

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    It will pretty funny to watch as someone tries changing one single resistor in the darlington network of an OM-1 meter. IF YOU CHANGE ONE RESISTOR, THEN ALL HAVE TO BE CHANGED. My success with the schotkey diode speaks for itself. I am not trying to sell my service on this. If I was I would not have mentioned 1N-6263 as the diode you would use. You can probably buy the diode for $1. That's all the information you need for the do-it-yourselfer. John

  9. #39

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    Quote Originally Posted by John Hermanson View Post
    It will pretty funny to watch as someone tries changing one single resistor in the darlington network of an OM-1 meter. IF YOU CHANGE ONE RESISTOR, THEN ALL HAVE TO BE CHANGED. My success with the schotkey diode speaks for itself. I am not trying to sell my service on this. If I was I would not have mentioned 1N-6263 as the diode you would use. You can probably buy the diode for $1. That's all the information you need for the do-it-yourselfer. John
    "Darlington network"? What is that? FYI, there are no transistors in that meter circuit. Could you perhaps be talking about the bridge circuit?

  10. #40

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    You do have a point about using the $1 diode, it is the simplest solution n I am sure will serve just as reliably but it has no educational value that way. Understanding how n why it works is key.

    So for the sake of sharing technical information, in depth, this thread is priceless since it has explored all the latest technology n even managed a schematic n reapir info of the circuit as printed by the manufacturer. Now it is on record, searchable for anyone needing this info in the future.

    .
    Anyone can make a Digital print, but only a photographer can make a photograph.

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