UV Lightbox Questions

Discussion in 'Contact Printing' started by bill schwab, May 26, 2006.

  1. bill schwab

    bill schwab Advertiser Advertiser

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    I've finally constructed a nice lightbox after using simple UV bulbs in suspended reflectors for some time. I went from a bank of 4 - 20w tubes to an array of 10 tubes. I used the original 2 ballasts I had been using and added to them 3 more identical ballasts for the extra 6 bulbs. Before, I was able to fire them up and they all started pretty much simultaneously. Now in the new box, they seem to fire randomly and it sometimes takes 20 - 30 seconds for all to fire. I do not seem to be able to get them to all fire at once and cannot feel confident enough to simply slide in my frame and turn on the timer. I have to fire it up, make sure they are all firing, cajole the ones that do not by touching the bulb... something I do not want to continuously do due to exposure to the UV.

    Anyone have suggestions or similar problems?

    I have gone basically from Jon Edwards' design as well as other similar ones I have found online. All bulbs are new and this seems to happen randomly. I have checked and rechecked the wiring, sockets, etc. If I could repeat this every time it would be easier to diagnose. I thought it might be a short due to having to touch the bulb to get some to fire, but as I said, it is random. Also, all it takes is a very light touch to make a bulb fire. It seems more the touch than the actually jiggling of a short.

    Any help or suggestions appreciated. I am baffled.

    Bill
     
  2. matt miller

    matt miller Subscriber

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  3. bill schwab

    bill schwab Advertiser Advertiser

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    Thanks Matt,

    I am willing to try anything. I'll post my findings. Thanks for the link to your thread, it looks as though this is my problem.

    Bill
     
  4. Kerik

    Kerik Member

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    Bill,

    You need some type of metal 'reflector' behind the bulbs to get them to light more quickly and uniformly. I used a piece of galvanized sheet metal in my 24x48 box w/12 tubes. If you already have the metal in place, something else is wrong - maybe Sandy will chime in...
     
  5. bill schwab

    bill schwab Advertiser Advertiser

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    Thanks Kerik, I have read the thread Matt pointed me to and it seems this is the problem. I used a nice, white piece of masonite behind the bulbs.... duh.

    Thanks again. Off to Home Depot for some sheet metal.

    Bill
     
  6. Kerik

    Kerik Member

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    Bill, if you haven't left for Homely Depot yet, you can try covering your white masonite with aluminum foil. That might do the trick. If your foil has a shiny and matte side, apply it with the matte side facing the bulbs.
     
  7. bill schwab

    bill schwab Advertiser Advertiser

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    !!!! Great idea Kerik!

    I'll give it a try.

    Bill
     
  8. bill schwab

    bill schwab Advertiser Advertiser

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    Aha!!! The foil worked. Not too pretty right now so I do think I will get that sheet metal. At least now I know it is going to work.

    Thank you both!!!

    Bill
     
  9. sanking

    sanking Member

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    Kerik,

    Very good idea. Another thing that might help would be to connect all of the tubes together with a piece of bare electrical wire. Just run it around each wire so that they all are in touch with the wire.

    I am going to assume that you also grounded all of the lights together with the green ground wire, and that you have this going to the outlet? If not, I would highly recommend you do this, both for more consistent start-up and for safety reasons.


    Sandy
     
  10. df cardwell

    df cardwell Subscriber

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    This is all really interesting... I'll be doing this project later this summer.

    It also explains the funny colors in the sky over in Bill's neighborhood :surprised:

    .
     
  11. bill schwab

    bill schwab Advertiser Advertiser

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    Oh yes Sandy... this has been done. I have now returned from the depot, cut my sheet metal to fit and run a wire from it to the ground as well. Works like a charm.

    Thank you everyone! Now I want a bigger one... :smile:

    Bill

    PS. Don... come on over when ready, the second one is always better.
     
  12. donbga

    donbga Member

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    Another simple solution for this is to run a bare heavy guage copper wire accross the top of the tubes connected to the ballast(s) ground. I've made three units this way and it works great!
     
  13. bill schwab

    bill schwab Advertiser Advertiser

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    Thanks Don! I actually tried that with the ground wire I had cut to attach to the reflector before installing the metal figuring it might work as well. It did work great. I will keep it in mind for the next one I build.

    Bill
     
  14. photomc

    photomc Member

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    Ah Yep! That's how mine is done...12x 20W BLB, 3 Fulham Workhorse -Electronic Ballast. Comes on and stays on with the flick of a switch, have not seen any changes in output - unless it is really cold, then it takes about a min to warm up (it's in my garage) and is not a problem right now (cold that is :wink: )
     
  15. sanking

    sanking Member

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    Better go ahead and build the bigger one now before you forget all the things you just learned. I built two smaller units before finally realizing that it would be an enriching experienice to have a unit made from 48" tubes.

    Sandy
     
  16. donbga

    donbga Member

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    Sandy,

    Where do you get paper long enough to use that size UV printer?
     
  17. bill schwab

    bill schwab Advertiser Advertiser

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    My thoughts exactly.
    :smile:

    B.
     
  18. sanking

    sanking Member

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    Don,

    I am not actually using the large UV printer to make huge prints. The main advantage is that it allows me to expose several prints at the same time. With the 48" length, for example, I can easily expose three or four fairly large prints at once. This is important for me since with my carbon printing I make thick tissue that require very long exposures, on the order of 15-30 minutes. Being able to expose three to five prints at the same time is tremendous saving of time and energy.

    Sandy
     
    Last edited by a moderator: May 27, 2006
  19. mark

    mark Member

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    What are the over all dimensions of a box that size, Sandy? Damn thing has to be really freaking big, if I am visualizing it right.
     
  20. donbga

    donbga Member

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    That makes sense in your case.

    My interest is to make long panos from stitched digital negs. Pictorico is supposed to be releasing 13 inch OHP in rolls this year and I want to print some images about 36 inches long. I'll look at paper suppliers for sizes. I pretty sure some papers come in 40-42" sheets.
     
  21. sanking

    sanking Member

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    Mark,

    Yes, it is pretty big, say about 51" X 29" X 9.5" and probably weighs around 50-60 lbs. I use it over a NuArc vacuum frame that is 44"X33". The NuArc frame is on rollers, so to place the negative in the frame I roll it out, load the negative and sensitized material, and then roll it back in to expose.

    Sandy
     
  22. sanking

    sanking Member

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    I have seen papers in 40-42" sheets. Also, Rising Stonhenge can be bought in rolls. Vague about the width, but was in the 36-40" range as best I can recall.

    Sandy
     
    Last edited by a moderator: May 28, 2006
  23. matthewbetcher

    matthewbetcher Member

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    Whether I go with the sheet metal or the bare copper wire, does this need to then be attached to the sockets? My ballasts are grounded and I was going to attach that ground wire into this copper wire for behind the tubes, but I guess my real question is... do the sockets need to be grounded as well?