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  1. #11

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    Just something to also be aware of is the frequency of the AC voltage in France is 50Hz whilst the frequency of the AC Voltage in the US is 60Hz, depending on the circuitry this may give rise to some timing errors.

  2. #12
    mr rusty's Avatar
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    depending on the circuitry this may give rise to some timing errors.
    No, it isn't using the frequency for timing! not a problem.

  3. #13
    Steve Smith's Avatar
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    Quote Originally Posted by mr rusty View Post
    Yes, I had a quick look on the web and it seems it is an 84V (or 82V) lamp on the 120V transformer.
    That's because it is in series with a diode so it is a half wave rectification of the 120 volt supply.


    Steve.
    "People who say things won't work are a dime a dozen. People who figure out how to make things work are worth a fortune" - Dave Rat.

  4. #14
    RH Designs's Avatar
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    OK, so it's a b+W head, not a dichroic so it doesn't use the 24v lamp. The idea of using a diode to drop 120v to 84v seems like a bit of a kluge to me but I know it was common practice in the US. The ideal solution would be to find a 220v lamp which would fit the enlarger's socket, chop out the diode and run the whole lot at 220v, but my knowledge of enlarger lamp types is too limited to be able to say if that's a viable option.

    I don't think you would need as big a 220-110v transformer as 1KW, the Analyser's consumption is negligible so you're really only running the 250W enlarger lamp so 500W should be more than enough.

    There is no problem with the frequency difference, our timers have their own internal clock and do not rely on the mains frequency.

    Edit: looking on the web I found this which suggests there is a stabilised power supply for the 82v lamp - if you have that, ignore what I said about the diode .
    Regards,
    Richard.

    RH Designs - My Photography

  5. #15

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    Thank you very much Richards, that's very helpful!

  6. #16
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    In low volume technical and scientific gear, which usually include photo gear, multi- tap transformers are rather common. They can usally be reconfigured to work with powere sources as found all over the world.

    Finding documentation to figure out what the different taps on the transformer do can be a challenge.

    I have more than a few times in the past bought 220/240 gear from overseas, even without the manuals for voltage conversion and converted them for my north american usage needs.

    I know this is not for everyone, but here is the basic approcach.

    I use an autotransformer (hooked to a GFI/RCD power source) to drive the device with the voltage it originally wanted, and measure the outputs going to the circuit board/rectifier section. Then I unhook the secondary termianls, and measure the voltage again.

    Look at the leads insulation colours, and try to guess which ones might be center taps.
    Look for leads on the primary tied together if coming from a 220/240 market.
    They are likely used to put two 100-140V primary windings into series.

    Unhook the links on the primary. Make ohm meter reading to figure which leads are part of the same winding, and whch ones are different.
    Then figure which ones are at separate ends of a winding, and which ones are likely neighbouring taps separated by only a few turns.

    (keep good notes/lots of digicam snaps, as you go.)

    Usually the 240/220 conversion is to take a primary OEM connections, wired in series, and modify it to connect it in parallel.

    Make educated guess trial connections on the primary, insulate unused leads, put the meter in AC volts mode, and hook it to the secondary leads that you have previously measure the output voltage of.
    Slowly wind up the voltage you drive the primary with from the autotransformer, and stop when you get the desired votage on the secondary. Then go and see what voltage you are feeding the primary. If it is your target voltage you are done. If it is some wierd voltage, then other tap connections that look promising from your ohn meter testing results should be trialled.

    Finally, once all is re-assembled, adjust the overcurrent fuse; it is likely going to need ot be doubled for a 220 to 120 conversion.
    Make note of any shaded pole motors for fans , etc. They may connect upstream of the transformer, and need special treatment. A small voltage step up transformer or surplus autotransfoeras I had, for one project can be added to drive them at 220V etc. if you are on 120V mains. .
    my real name, imagine that.

  7. #17
    Steve Smith's Avatar
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    Quote Originally Posted by RH Designs View Post
    The idea of using a diode to drop 120v to 84v seems like a bit of a kluge to me but I know it was common practice in the US.
    It seems very strange to me too. Just make a 120 volt bulb!


    Steve.
    "People who say things won't work are a dime a dozen. People who figure out how to make things work are worth a fortune" - Dave Rat.

  8. #18
    RH Designs's Avatar
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    Quote Originally Posted by Mike Wilde View Post
    In low volume technical and scientific gear, which usually include photo gear, multi- tap transformers are rather common. They can usally be reconfigured to work with power sources as found all over the world.
    Funnily enough I recently had occasion to find that out - I wanted a quick cheap and cheerful 110v power source and thought the transformer for my LPL 7700 might have a tapped transformer. It doesn't, it's a simple 220v in/12v out. I then looked at a Meopta 12v transformer labeled "220v" and found that it had two primary windings wired in series. So that would be a simple conversion to 110v if required - and it also provided me with the 110v I needed by using the primary winding as an auto-transformer.
    Regards,
    Richard.

    RH Designs - My Photography

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