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  1. #11
    Donald Qualls's Avatar
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    Quote Originally Posted by lee
    I dont think there is anything in this electro-mechanical timer to blow with the cold light. This is not the timer I would pick to use with an enlarger but sometimes we must do what we must do.
    Lee, I presume you're referring to the fact I'll have to reset the timer for each exposure, but given I'm split filtering, I'd have to do that anyway for the blue and yellow filter exposures -- and I've been led to understand that the little Time-o-Lites that do reset are *not* suitable for cold lights, due to low rated contacts. Sure, what I'd like to have is a head with blue and green LEDs and separate timers for the two (then I could use Time-o-Lites, because the LEDs draw only a few hundred milliamps at the 125 V supply level), which would also eliminate filtering and such... Maybe in 2007...
    Photography has always fascinated me -- as a child, simply for the magic of capturing an image onto glossy paper with a little box, but as an adult because of the unique juxtaposition of science and art -- the physics of optics, the mechanics of the camera, the chemistry of film and developer, alongside the art in seeing, composing, exposing, processing and printing.

  2. #12
    lee
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    Quote Originally Posted by Donald Qualls
    Lee, I presume you're referring to the fact I'll have to reset the timer for each exposure, but given I'm split filtering, I'd have to do that anyway for the blue and yellow filter exposures -- and I've been led to understand that the little Time-o-Lites that do reset are *not* suitable for cold lights, due to low rated contacts. Sure, what I'd like to have is a head with blue and green LEDs and separate timers for the two (then I could use Time-o-Lites, because the LEDs draw only a few hundred milliamps at the 125 V supply level), which would also eliminate filtering and such... Maybe in 2007...
    Donald,

    you asked a question and I gave you an answer and judging from the others above here, my answer was ok. I have used Time o lites in the past also with aristo heads. Sorry you did not like my answer.

    lee\c

  3. #13
    Donald Qualls's Avatar
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    Lee, it wasn't that I didn't like your answer, I just wasn't sure I understood it.

    I now understand you to be saying Time-o-Lite's work fine with cold light? That's opposite what I had previously heard, but it'd be good news (though I still need to find a way to store two settings if I want to use the resetting feature with split filtering, since I can't reregister the paper to be able to do all the blue, then all the yellow for a series of prints).
    Photography has always fascinated me -- as a child, simply for the magic of capturing an image onto glossy paper with a little box, but as an adult because of the unique juxtaposition of science and art -- the physics of optics, the mechanics of the camera, the chemistry of film and developer, alongside the art in seeing, composing, exposing, processing and printing.

  4. #14
    lee
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    sorry the internet is not a friendly place for understanding each other. My apologies. yes I have used the Time-o-lite with the Aristo cold light head. I dont think there is a way to store 2 separate times with the Time-o-lites I have used. I would suggest writing the separate times on a piece of paper and just making one exposure with one filter and changing the time and the filter and making the next filter. good luck on your quest.

    lee\c

  5. #15

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    Quote Originally Posted by Donald Qualls
    Gralab Model 300 darkroom ... data plate shows: 750 W, 6 Amps, 3 Amps "T". I presume "T" refers to the timer switched circuit
    The 'T' designation on a contact normally means 'tungsten'. In this case the maximum incandescent wattage is 360Watts [120v x 3A]. Lightbulbs have a very high current when they are turned on and can weld the contacts shut if the contact current is not derated.

    A cold light head's inductance causes a problem when the circuit is opened/turned off. The current in the head wants to keep going - think flywheel - and as the contacts open the current forms an arc accross the contacts causing pitting. A capacitor/resistor [called a snubber] accross the contacts will quench the arc. If you remember old car ignition systems there was a capacitor accross the distributor points and this was required because of the inductance of the ignition coil.

    If you are worried about the timer/head combination I would contact the manufacturer of the head.
    Nicholas O. Lindan
    f-stop enlarging timer - http://www.nolindan.com/da/fstop/index.htm

  6. #16
    Donald Qualls's Avatar
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    Nicholas, I e-mailed Gralab a few days after I got the timer. Still haven't had a response. No idea how to contact Zone VI -- who handles that brand now?

    However, it's good to know what the T is for. Not sure I'd want to put a capacitor across the terminals of an AC device -- how do they quench the arc in a common light switch? Oh, wait -- you mean the capacitor in parallel with the switch, so it conducts for a fraction after the switch opens. Yeah, if I could get the case open I could not only easily check if there's a snubber in there, but solder one in if there isn't. Unfortunately, Gralab though blind rivets would be a nifty way to close the case quickly and cheaply, so I'd have to drill those out to open the timer. Still, I've got a setter for those, and the fasteners are cheapish...

    How would one calculate the value for a snubber?
    Photography has always fascinated me -- as a child, simply for the magic of capturing an image onto glossy paper with a little box, but as an adult because of the unique juxtaposition of science and art -- the physics of optics, the mechanics of the camera, the chemistry of film and developer, alongside the art in seeing, composing, exposing, processing and printing.

  7. #17
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    Donald, is the Gralab 300 timer the big square black box type timer you bought? I have three and I have used it with a Aristo cold light on my Beseler 45m, it's an electro/mechanical timer and can handle the inductive load. If you use it and burn out the timer let me know and I will send you one.

    Curt

  8. #18
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    Quote Originally Posted by Donald Qualls
    How would one calculate the value for a snubber?
    Donald, Practically every snubber network I have ever seen or used has been 100 ohms in series with 0.1uF (100nF). I don't think the values would be very critical in this case (or most other cases).

    Regards,

    Steve Smith.

  9. #19
    Donald Qualls's Avatar
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    More to the point, Steve, I'd expect those values to be pretty much universal for a reasonable loads on 120-240 V service -- it's not that the capacitor needs to store much charge, it just has to take the current long enough for the physical contacts to separate beyond arcing range.

    Curt, yes, the Gralab 300 is a biggish black square box.

    I've gotten lots of opinions that the Gralab is fine with the cold light (and mine certainly seems to be okay), and some folks saying even the little Time-o-Lites are okay. BTW, I think I found a way to use two Time-o-Lites to do repeated split filter printing, assuming they have a "focus" setting that turns on the lamp. You'd hook them up in series (that is, plug one timer into the switched outlet of the other, then the enlarger lamp into the second timer), and set the blue and green times; for the blue exposure, set the "green" timer to "focus" and then swap to expose with the green filter. Lacking a focus setting, you could rig a box with a double-pole, double-throw switch to connect both supply and lamp hot wires alternately to the two timers, and just flip the switch back and forth from "green" to "blue" -- use a three-throw setup and you could add a "focus" position.

    However, since I don't do many multiples (yet), the Gralab with manual setting for each exposure is currently working fine.
    Photography has always fascinated me -- as a child, simply for the magic of capturing an image onto glossy paper with a little box, but as an adult because of the unique juxtaposition of science and art -- the physics of optics, the mechanics of the camera, the chemistry of film and developer, alongside the art in seeing, composing, exposing, processing and printing.

  10. #20

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    If you want to do split filter printing with a single timer, provided the timer has a safelight output, you can wire the enlarger lamp in parallel to the two outputs. You could use a delay on break solid state timer on the enlarger lamp output only and use a delay on make solid state timer in series on the safelight output.
    Art is a step from what is obvious and well-known toward what is arcane and concealed.

    Visit my website at http://www.donaldmillerphotography.com

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