Flickering Cold Light Head

Discussion in 'Darkroom Equipment' started by Jesse, Aug 14, 2011.

  1. Jesse

    Jesse Member

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    I have a Beseler 45MXT with a Zone VI cold light head and Zone VI compensating timer. I am in the process of getting my first darkroom set up .When I set up the cold light head and timer and turn on power I get a flickering when the light dial is turned all the way up .Is this normal ?Will it eventually go away ?Or do I need to look for another light source?I have had the enlarger and head and timer in storage for awhile till I could set up a dedicated room.This is also the second cold light head I have .The first did not flicker like this before the bulb broke .
     
  2. Cruzingoose

    Cruzingoose Member

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    If a fluro tube has not been used for a long time, it will flicker a bit untill it restabilizes. This can take an hour or so. Leave the covers off and let the lamp run on high. Check it every 10-15 minutes to see if the flickering stops.
     
  3. ChuckP

    ChuckP Subscriber

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    Does it flicker when plugged directly into the AC with no timer?
     
  4. Jesse

    Jesse Member

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    Just checked it out .The head does not flicker when plugged directly into an AC outlet.
     
  5. jk0592

    jk0592 Member

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    My Zone VI cold head with Zone VI stabilizer does not flicker at all, and the main power supply to the head goes trough a very old gralab (300?) timer.
     
  6. Jesse

    Jesse Member

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    Does the Zone VI Compensating timer have a voltage stabilizer built in? Or is that a seperate piece of machinery.
     
  7. jk0592

    jk0592 Member

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    It is a different piece of machinery. It adjusts the cold light output to be constant; the timer you use adjusts (compensates) the time for the variability in output. Is your cold light approaching the end of life (10 000 hours) ?
     
  8. Jesse

    Jesse Member

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    No the head was purchased new after the original lamp broke after a fall. The old one didn't do that .And the new one was put into storage shortly after being bought before even being used other than plugging it in to see if the light came on after receiving it .
     
  9. paul ron

    paul ron Member

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    I say let it run a long time on your timer, maybe it will stabilize.

    BTW The preheater has to be pluged in as well you know and warmed up for a few minutes too?

    If it isn't flickering when plugged directly into an outlet, it's got to be the timer/stabilizer at fault. Does this head have a light sensor built in like the Zone VI?

    .
     
  10. Jesse

    Jesse Member

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    The cold light head is a Zone VI and it does have the photocell. When I plugged it into the AC outlet I plugged in both the Lamp and Pre Heater lead. What does this stabilizer look like?Would it be placed between the outlet and the timer or between the timer and the lamp?
     
  11. john_s

    john_s Subscriber

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    The Compensating Timer does not adjust the lamp's level. The earlier Stabilizer did that, by reducing the level to the level that would be maintained once the lamp was moderately warm. In other words, it cut the "peaks" and the "troughs" to the level just below the troughs. Advantage: stable light. Disadvantage: not much light. Exposures could be long.

    The Compensating Timer allows the lamp to fluctuate and by monitoring the lamp intensity via the sensor it adjusts the length of a unit of time to supposedly give constant exposure. I used to use one and the audible ticks that marked the end of each unit of time (that you could regard as nominal "seconds") went from slow to fast during even a fairly short exposure, as a result of the tube heating up.

    As an aside: I now use an Aristo VCL4500 2-tube VC cold light head. I have noticed that the lamps are much less subject to rise in output with increasing temperature. Maybe (guess) the newer Aristo tubes that are more suitable for VC filters are also more stable.

    I have scans of some Zone VI instructions for the Stabilizer and the original head if anyone is interested.

    CORRECTION: The Compensating Timer, although it does not constantly adjust the lamp intensity via feedback from the sensor, does have a Lamp intensity control, from Min to Max or something like that. I would suspect that this is where the flickering comes from. Does it flicker when Lamp is set to Max?
     
  12. Jesse

    Jesse Member

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    Yes .The lamp flickers when it is set to maximum. I wouldn't mind a copy of those instructions. Only instructions I received when I bought the equipment from an estate sale was the manual for the enlarger.
     
  13. ChuckP

    ChuckP Subscriber

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    You don't need a stabilizer with your timer. It already will compensate for any light drift by varying the time. Are both the intensity and dry-down dials turned all the way up? Maybe run the dials up and down several times with the timer off. You may have a dirty potentiometer. Does the head flicker if the intensity is adjusted off max? The lamp AC does go through the timer so you can adjust the intensity. So it's possible that something in the timer is causing the flicker especially since the lamp works OK plugged directly to AC. Maybe you can plug a 75 watt incandescent lamp into the timer output and with the cold light plugged directly to AC operate the timer and see if this lamp flickers. You will need to run the cold light because I believe that the timer will not run without an input from the photocell.
     
  14. jk0592

    jk0592 Member

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    I have checked with my Zone VI cold light and stabilizer. The light flickers only when set at the very very lowest possible intensity (it is so low as to be impractical), as if one is trying to turn the light off via the dials instead of cutting power altogether. As soon as the intensity dial is moved slightly, the flicker stops. I think there is something wrong with your timer ( tiktok ? ).