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  1. #11
    AgX
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    To my understanding there are two kinds of regulators for a rather high drain:

    -) a servo-controlled regulating transformator. I guess accurate but slow.

    -) a resonating loop transformer. This device lacks any mechanics, is fast but only reduces the variations on the incoming voltage.




    Quote Originally Posted by panastasia View Post
    I have a Vivek voltage stabilizer (model 110; 750w max.) that maintains a constant 100v output (dims the light source). I only used it for doing color printing as voltage fluctuations cause color shifts.

    Why has your device a lower out- than input?

  2. #12
    sly
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    A UPS may be a better solution in such a case, but IDK for sure.

    No idea what you are talking about here - I know what a plug is, and a light switch, and I know where to find the box to turn the electricity off if someone is going to fix something for me.

    Test strips get you very near the ballpark, but full time exposures must be made for final tweaking (one more test strip will exposures closely bracketing the time the previous one indicated), or you need to print intermittently exactly as you did to arrive at the strip you like. How much difference there is between a full time exposure and a test strip exposure is directly relative to how many times the enlarger is cycled, and the on/off characteristics of the particular enlarger lamp.[/QUOTE]
    I have often done a 10-11-12 type teststrip, after doing the 4,6,8,10,12,14 one, just to pin things down, so I guess my instincts were right, even if I didn't know all the reasons.


    Isn't APUG wonderful? I've learned more in the last 8 months that I've been a member here, than I did in years of mucking about in photography, repeating my mistakes and misunderstandings. Thank you everybody!

  3. #13

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    Quote Originally Posted by AgX View Post
    To my understanding there are two kinds of regulators for a rather high drain:

    -) a servo-controlled regulating transformator. I guess accurate but slow.

    -) a resonating loop transformer. This device lacks any mechanics, is fast but only reduces the variations on the incoming voltage.


    Why has your device a lower out- than input?

    Agx,

    Think of the sine wave associated with AC (alternating +110v to -110v) with the plus and minus peaks chopped off. If you chop off +10v and -10v you end up with 100v AC; the amplitude of the wave is reduced. Analogy: It's like shaking a rope back and forth through a window - the window confines, or reduces, the lateral movement of the rope - thus changing (reducing) the maximum limits of the ropes movement (the amplitude).

    The the regulator/stabilizer will not allow any current fluctuation greater than the 100v amplitude.
    Last edited by panastasia; 02-17-2008 at 06:59 PM. Click to view previous post history.
    "Pictures are not incidental frills to a text; they are essences of our distinctive way of knowing." Stephen J. Gould

  4. #14
    AgX
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    But your concepts means that there only will be protection against voltage peaks, not drops. Am I right?

    And with a transformer you can change an incoming voltage (110VAC) to a lower voltage (24VAC).
    But also transfer a high voltage (110VAC) to another high voltage (110AC) in the form of a separeting transformer.

    If in both cases the transformer can be regulated I don’t see why there should be any voltage drop (beyond any intended drop) at all. Or at least not when the incominng voltage is at standard level (as that 2nd [resonator]technique seems not to be able to cope fully with variations).

  5. #15

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    Quote Originally Posted by AgX View Post
    But your concepts means that there only will be protection against voltage peaks, not drops. Am I right?

    And with a transformer you can change an incoming voltage (110VAC) to a lower voltage (24VAC).
    But also transfer a high voltage (110VAC) to another high voltage (110AC) in the form of a separeting transformer.

    If in both cases the transformer can be regulated I don’t see why there should be any voltage drop (beyond any intended drop) at all. Or at least not when the incominng voltage is at standard level (as that 2nd [resonator]technique seems not to be able to cope fully with variations).


    I'm not sure but I think your confusing AC with DC current; AC has two peaks, it alternates between plus (positive) and minus (negative) very fast - 60 cycles/second - appearing to be continuous (a sine wave). With less cycles you would actually see the the light source blinking off and on. In the US we have AC.

    Also, my particular stabilizing unit has no adjustment - it's self regulating - it has only one function.

    My knowledge regarding electronics is weak, therefore, I can only communicate at my level of understanding. Maybe someone else with more knowledge and the ability to explain it in more detail can jump in here. For how DC current is stabilized I would only be guessing. Even though I have a background in engineering, mostly mechanical, I tend to avoid electro-mechanics. It doesn't interest me enough because electicity is something I can't see, unless it manifests as something like lightning.
    Last edited by panastasia; 02-18-2008 at 06:43 AM. Click to view previous post history.
    "Pictures are not incidental frills to a text; they are essences of our distinctive way of knowing." Stephen J. Gould

  6. #16
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    Quote Originally Posted by sly View Post
    Some help and advice from the electronically minded please!

    I noticed today that my prints, exposed for the same length of time, were not consistent. I realized that it was due to the heater kicking in. My darkroom is in an outbuilding. No concerns in the summer - no heater. No concerns in the winter - heater going full blast constantly just to keep room warm enough to work in. Last fall we were off camping for along time - and once home spent much time developing negatives taken on trip. So now the weather is starting to warm up (sorry Eastern and Prairie Canadians - I know you're still getting dumps of snow while we are getting snowdrops) and I'm realizing I have a problem - some heat needed, but not constantly. Today I dealt with it by turning heater off while doing exposures and on while selecting neg, cropping, focusing, etc. It worked, but I know I can't count on myself to remember every time, and I will blow many exposures.

    When I got this darkroom setup last year it came with a surge protector. (At least I think that is what that big, heavy, rectangular thingy that the enlarger and timer can be plugged into is.) I used it at first but it made me distrust my test strips as each time the enlarger came on you could see it "power up" - the image would go from dark to bright in a fraction of a second each time. It seemed that each 2 second exposure on the test strip was actually just a bit less than 2 seconds at full intensity, so if, say 16 seconds looked good - the only way to match it would be to do 2 second increments, rather than 16 seconds. Am I making any sense? And then I'd have to take dry down into consideration too. So I unplugged it. Do I need to plug it back in, and what about the power up time - how would I compensate for that? Would the kind of surge protector power bar I have my computer plugged into do the job any better?

    Thanks to anyone who has words of wisdom for me.

    Sly
    Just a couple of question before i try and address the problem,
    1) With enlarger already on for a little while, (~10 secs) is the enlarger lamp dimming at the exact moment that the heater comes on?
    2) If so, does it stay dim while the heater is on or does it just dim momentarily and then return to it's original brightness?
    3) With the enlarger AND HEATER already on for a little while, (~10 secs) What happens to the enlarger lamp brightness when the heater is switched off?
    4) What sort of heater is it? Radiant filament, oil-filled radiator etc?

    Let me know how the enlarger behaves under the above scenarios.
    The problem may be related to old or incorrect electrical wiring or it may be a little bit more complicated such as your heater's inrush current (electrical current that the heater draws just after it is switched on) which is introducing fluctuations on your power supply.

  7. #17
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    Sorry: there are so many things going on here, lets get back to basics...

    My initial suggestion is to plug your stabilizer/regulator back in. It can't hurt (assuming it is compatible in voltage and power rating with the enlarger).

    Be aware that all lamps take time to ramp up to full brightness. Likewise, they take a significant fraction of a second to ramp down. Regardless, with or without the stabilizer, 10 lots of two-second exposures are not the same as a single 20 second exposure.

    A simple test would be to expose a piece of paper with no negative in the enlarger to a very feint grey with the heater off (stop the lens well down) to just above paper base white and then do it again for the same time and f-stop with the heater switched on and see if there is any difference. You could also try switching the heater on half-way through. If you have a transmission step-wedge you could get an idea of how much difference there is, but that is probably over-kill...

    This should tell you if there is a significant problem with voltage fluctuations, or not. By exposing the paper to just above base white you are in it's most sensitive area and it is easy to see any change.

    Have fun, Bob.

  8. #18

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    I thought the problem of voltage fluctuations was already established.
    "Pictures are not incidental frills to a text; they are essences of our distinctive way of knowing." Stephen J. Gould

  9. #19
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    There is a lot of theorizing about types of stabilizer and regulator but no clear indication of where the source of your problem may lie. You have seen differences in prints but it is not clear where these differences are coming from judging from what I have read - just one or two assumptions.

    Eliminating each potential source of a problem one at a time is the best way to approach a problem. Testing tells us what is actually happening, rather than what we think might be happening. If the test confirms one's suspicious, all well and good. If they show the assumption was wrong, even better - less wasted time! Either way, you know for sure one way or the other and can proceed with confidence.

    Cheers, Bob.

  10. #20

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    You could try an AC relay, big enough for your heater, controlled by the enlarger timer. When the enlarger is on the heater is off. Like the function that turns off the safelight when the enlarger is on. Since the enlarger is on for only short times the heat should still stay pretty constant.

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