Coldlight Transformers

Discussion in 'Darkroom Equipment' started by waynecrider, Jun 20, 2006.

  1. waynecrider

    waynecrider Member

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    Coldlight Voltage Supply

    I pulled apart my 4x5 graflarger to clean things up and noticed that the power cord wiring was brittle and cracked. Upon cutting the cord back to find wiring that was good I wound up cutting it all the way back, and since it is a tar encased enclosure it is now trashed. Does anyone have any idea on just what ballast would be needed to push a cold light or Aristo bulb. I emailed Louise Kessler at Aristo and she either can't or won't tell me. I also asked about buying a power supply if they made them. It's just funny that you manufacture something and don't know what kind of power supply it takes to power it. Spec's on the Graflarger were 115V, 75va, unknown voltage output. I tried checking the voltage but got conflicting readings. Thanks
     
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  2. pnance

    pnance Member

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    Cold light heads are florescent lights. Thus, they don't have a transformer, they have a ballast. Instead of changing the voltage up or down as a transformer does, the ballast (which actually is a lot like a transformer, except there is only one winding) limits the current flow of the tube. Also involved is a starter mechanism to allow the initial higher current flow.
     
  3. waynecrider

    waynecrider Member

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    The Graflarger has 2 leads to the tube, most ballast for single tube that I see have 4. Any suggestions?
     
  4. pnance

    pnance Member

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    Yes, the common florescent light has a filament on each end. The ballast is in series with the ac power and one side of each filament. The other two leads of each filament go to the starter device. Its job is to open after the tube fires, shutting off the filament current.

    I don't know the circuity of the cold lights.
     
  5. waynecrider

    waynecrider Member

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  6. cdholden

    cdholden Member

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    Wayne,
    I've seen a lot of fluorescents (lots of work in commercial building environments), and only ever noticed one starter per ballast. I can't think of where I've ever seen a second starter without a second ballast as well.

    Maybe this helps:
    http://home.howstuffworks.com/fluorescent-lamp4.htm

    Chris
     
  7. waynecrider

    waynecrider Member

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    Thanks Chris. The Graflarger must be a rapid start design without a normal starter switch.
     
  8. epatsellis

    epatsellis Member

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    wrong, wrong, wrong, just think neon, as in neon transformer, there should be a rating plate somewhere, typically in thousands of volts and milliamps. Of course take what I say with a grain of salt, :wink: I've only worked in the sign trade for 20 years, including working with neon. And am building a cold light head for my 8x10 elwood.


    erie
     
  9. Loose Gravel

    Loose Gravel Member

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    Erie is onto to something. Cold cathodes are different than conventional fluorescents. Coldlights are light a lamptop backlight, except longer and therefore higher voltage. Be careful measuring the voltage unless you volt meter can take thousands of volts. Check with Mr Neon. He can help. This can probably be fixed.
     
  10. waynecrider

    waynecrider Member

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    Unfortunetly there is no rating plate, just the input voltage and VA; That's it. I think I'm up the creek here, but would love to work it out. If your making a coldlight head, what's your transformer spec's, not that i would use it. Is the transformer capacity based on tube length or gas that's inside?
     
  11. epatsellis

    epatsellis Member

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    the transformer ratings depend on tube dia. length and # of electrodes, one option, if you're totally buggered is to invert the xfrmr, bake it at about 250, above something to catch the tar, replace the cord, then re pot it
     
  12. Curt

    Curt Subscriber

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    Funny how Aristo can't say what the rating is; I have an Aristo 8x10 head with separate transformer and they can't tell me anything about it even though I have a model number label on it.
     
  13. GeorgesGiralt

    GeorgesGiralt Member

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    Hi !
    What I write will be from a very old Durst cold light head, so take it accordingly !
    This cold light head has a transformer getting 220 V 50 Hz input (France mains) and providing a little more than 2000 V. I have not measured the current flowing through the tube. I measured this becaus the head gives a too blue light output unsuitable for VC paper and I planned to replace t by a custom made Aristo V54 tube. So I thought Aristo would have asked me the power output of the transformer... NOPE ! they told me they can make a bulb if I provide them with the shape, lenght and tube dia. Not the voltage nor current ! Funny isn't it ?
    May I suggest you find a neon signs maker in your town and show him the beast, asking for help ? He may know what kind of insulation is needed, the power requirments and so on... He may also be able to re pot the thing.
    Just my 2 cents here...
     
  14. waynecrider

    waynecrider Member

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    It's in the trash and gone... Would have been a good idea tho.

    I think that maybe a sign maker might help. My next best bet is a custom LED board to fit the enclosure. I'm researching that as well, and it may prove to be a good way to go. I also have someone with a coldlight head that wants to sell it; We'll see.

    GG, I could believe the voltage.
     
  15. epatsellis

    epatsellis Member

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    I don't know, 2000 sounds low, the smallest I've used is about 4500v, though they could be using a custom.


    erie
     
  16. waynecrider

    waynecrider Member

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    Just to add info to the thread, the bulbs are apparently made by the following company for Aristo. http://www.voltarc.com/ The contact address for Louise Kessler is at the bottom of the Aristo page.

    I have contacted a local neon guy and it looks like I may have a solution. May is the operative word.
     
    Last edited by a moderator: Jun 21, 2006
  17. Donald Miller

    Donald Miller Member

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    While these two companies may have different names, they are one and the same company.
     
  18. Donald Miller

    Donald Miller Member

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    I seem to remember 3.5 KV on the transformer output...amperage should be very low with that high an output voltage...

    Another source would be the step up transformer that is used in boiler burner ignition systems...they use the same types of transformers...

    For those who may be confused by terminology...a ballast is simply another word for a step up transformer..
     
  19. epatsellis

    epatsellis Member

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    IIRC, when I did the pattern from my 8x10 head, basically a 16" circle with a grid 1 1/2" on center, it came to 9000volts, 45ma, a 12,000 will give me a little bit of insureance against line sags, etc. now realize that this grid is quite a bit bigger than a 4x5 head, so a 4500v xfrmer would work. one thing to consider is a core and coil type tranny, basically the same trans without the potting, about 1/2 to 1/3 the price, though. However, you are responsible for best practices with regard to insulation,etc. (iirc, dielectric voltage of air is ~1000v /in.) a decent neon guy could help you quite a bit and probably has a few (dozen or more) used trannies lying about, Iknow I have at least 10, and a friend of mine that does a lot of neon has 2 or 3 pallets of them. (they don't often fail, but I know I won't use a used transformer in a new installation.) France also makes a line of transformers that are totally enclosed with a line cord and switch, and has 2 gto wires coming out of it.


    erie
     
  20. RichSBV

    RichSBV Member

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    erie is 100% correct. The Graflarger is NOT flourescent, but a simple neon tube (of course the gas inside may be special).

    You have three direct options.

    Measure the voltage out of a working transformer. I do not recommend this unless you know how...

    Take your Graflarger, complete, to a neon sign shop and ask them for a transformer. They can guess, wire it and hopefully not blow it up.

    Check on graflex.org where this discussion has gone around many times...

    The best I can remember is the voltage runs between 3.5 and 6 thousand volts. It is not all that critical to operation except where it may blow the tube, wear it out prematurely or not ignite it. The milliamp rating is also not all that critical except to be high enough to maintain the voltage through the tube. So if it's rated at 75VA and you find a replacement at 80VA, fine, but 60VA might not work...

    There was a person on gralfex.org who found a replacement. I don't remember the specifics but a search there would turn it up...

    ... So I should have noticed a 'page 2", and tried spell checking...
     
  21. pnance

    pnance Member

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  22. Loose Gravel

    Loose Gravel Member

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    You can make your own HV meter probes by dividing the voltage by 100:1. Do this with some high value resistors. Don't forget to figure in the volt meters input impedance and the resistor's power rating. Also, keep one hand in your pocket.
     
  23. Chan Tran

    Chan Tran Member

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    When you deal with voltage in excess of 1000V you should use wires that has insulation rating sufficiently to ensure safety. Most wires are rated for 300V or 600V only.
     
  24. waynecrider

    waynecrider Member

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    Yea, and now I know why I couldn't get a reading!

    I was able to track down the thread over in Graflex.org concerning a replacement Graflarger transformer and after a little detective work found that the one the guy bought is no longer being made. Essentially it was a solid state self regulating transformer of which there appears to be a few around with capabilites up to 15KV and beyond. The problem remains, just what voltage and millamperage did this thing run at? There was a thread that mentioned 3000V, but who knows. I've emails out and a local neon guy to talk to tomorrow.
     
  25. epatsellis

    epatsellis Member

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    if you bring the tube, or head with you, the neon guy can hook up a milliamp meter, and determine which size transformer in about 20 seconds.


    erie