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  1. #11
    ic-racer's Avatar
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    Quote Originally Posted by paul ron View Post

    Measuring the temp of the housing is not what the heater is for.. it's the balast that has to be hot to fire it up faster.
    WIth respect to the Aristo 1414 head pictured the light output is proportional to the temp of the bulb up to a certain temp beyond which the light output becomes inversely proportional to the bulb temp. The housing temp is proportional to the bulb temp. The ballast is not in the housing, it is on the floor and stays cold.

  2. #12

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    Your cold light has no balast transformer in the head?... I think that is strange since the manufactures want both bulb n transformer to stay warm for quicker starts. Generally the heater is on a separate line, is that plugged in? You aren't mixing up the balast transformer with the power supply or conditioner or comp timer?

    I found someting interesting about the airista heater in a cold head...
    http://www.light-sources.com/sites/d...nting_info.pdf

    It's interesting about the light output as the heat goes up. I'll have to check my Zone head vs the Arista to see if this is typical of the bulb or just the Aristas. Mine are are both the round housings for the Besseler 45. I also have the old tubes in both, the W45.
    Last edited by paul ron; 04-07-2012 at 07:44 AM. Click to view previous post history.
    Anyone can make a Digital print, but only a photographer can make a photograph.

  3. #13
    Nicholas Lindan's Avatar
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    The purpose of the ballast is to supply a somewhat constant current to the lamp. The temperature of the ballast has no effect on light output. If anything a cold ballast will work better than a hot one, though the difference is minuscule.
    http://en.wikipedia.org/wiki/Ballast_%28electrical%29

    A cold lamp is at low internal pressure and operates at a low voltage - as the lamp warms up the pressure of the gas in the lamp increases and the mercury and the other metals vaporize, adding to the gas pressure. The voltage of a plasma - the glowing gas in the lamp - is proportional to pressure. As power = voltage x current, the higher the lamp voltage the greater the lamp power. If the lamp gets too warm, and the lamp voltage rises, the current through a simple ballast will decrease somewhat thereby reducing the power to the lamp.
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  4. #14
    ic-racer's Avatar
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    Quote Originally Posted by paul ron View Post
    Your cold light has no balast transformer in the head?... I think that is strange since the manufactures want both bulb n transformer to stay warm for quicker starts. Generally the heater is on a separate line, is that plugged in? You aren't mixing up the balast transformer with the power supply or conditioner or comp timer?

    I found someting interesting about the airista heater in a cold head...
    http://www.light-sources.com/sites/d...nting_info.pdf

    It's interesting about the light output as the heat goes up. I'll have to check my Zone head vs the Arista to see if this is typical of the bulb or just the Aristas. Mine are are both the round housings for the Besseler 45. I also have the old tubes in both, the W45.
    Yes you should check that and see. The thermostat controlling my 1414 heater (the heater being just a few power resistors shorting the mains) came set around 35c. From there the lamp gets slightly dimmer as it heats beyond that temp. Other cold cathode systems may share a similar behavior. They recommend limiting lamp-on time to under 5 minutes. The 1414 transformer is quite massive and sits in a tray by the floor on the legs of the enlarger. The special cables to the head carry 400v.


  5. #15

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    WOW! Both my 4x5 cold lights have small balast transformers built into the head, no where near as massive as yours. My 8' florecent ceiling lights have noting that big either.

    Thanks for the FAQ on cold lights.
    Anyone can make a Digital print, but only a photographer can make a photograph.

  6. #16
    Bill Burk's Avatar
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    Do the lamps get hot enough to pop a neg in a glassless carrier? The Omegalite-D, because it is a large round bulb, stays cool. Sounds like they might. If I were to replace it with a grid-type fluorescent, I might introduce a neg popping problem that so far hasn't plagued me...

  7. #17

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    Very clever work. Another option would be to go with LED's which are more stable than fluorescents, run cooler, last longer and require less energy to run. Toward this end I have nearly finished an LED diffusion head for the Omega D series enlargers which I plan to offer for sale soon at a reasonable price. It works fairly well now but I would like to bump up the light output a bit using the new Cree XM-L series of LED's. Also I need to tweak the LED placement a little to get absolutely uniform brightness but otherwise it is done. Attached are photos of what it will look like. Power consumption is about 25 Watts from an external power brick and light output will be about 1000 lumens.
    Attached Thumbnails Attached Thumbnails IMG_1363.jpg   IMG_1364.jpg   IMG_1345.jpg  

  8. #18
    Bill Burk's Avatar
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    Quote Originally Posted by cardiomac View Post
    Very clever work. Another option would be to go with LED's which are more stable than fluorescents, run cooler, last longer and require less energy to run. Toward this end I have nearly finished an LED diffusion head for the Omega D series enlargers which I plan to offer for sale soon at a reasonable price. It works fairly well now but I would like to bump up the light output a bit using the new Cree XM-L series of LED's. Also I need to tweak the LED placement a little to get absolutely uniform brightness but otherwise it is done. Attached are photos of what it will look like. Power consumption is about 25 Watts from an external power brick and light output will be about 1000 lumens.
    Nice work!

  9. #19
    Bill Burk's Avatar
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    Still working out the rhythm of it, but basically I'll leave the lamp on for a couple minutes as if focusing/composing... Then check for stable ohms and make test strip. After the enlarger is off for 5 minutes or so (processing the test strip), it takes only about a minute in focus mode to reach the stable ohms again... Then I switch to time and put the paper in and print.

    One print tonight I forgot to warm it up and noticed right away the ohms were "high", so after the alotted time I just hit "focus" and added a third-stop's worth of light at the end. Came out OK.

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