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  1. #1

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    Question on Ballasts

    In building a UV lightbox using F20T12 BL tubes, I was looking at two different ballasts. The first is a RL2SP20 TP, which has a ballast factor of .61 and the other is a HM2SP20 TB, which has a ballast factor of .85. With limited knowledge, it seems that the higher the ballast factors the more light output.
    So my question, is there much difference in printing time using one or the other, this is for platinum/palladium printing. There have been some excellent discussions about the tubes, but I couldn’t find much on ballast. Any help would be appreciated.

  2. #2

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    Ballasts come in two types, 'electronic' and 'magnetic'. The 'magnetic' ones are cheaper. The 'electronic' are better. The are more efficient and have less flicker. You can get them for approximately $20 at a home improvement store. I don't know about the ballasts you mention, but the more efficient one sounds like an electronic one. If so, I'd get that one. Btw., both types are electronic, as in they use electricity. For some reason, though, that designation is still used to name a type of ballast.

  3. #3

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    Thanks Peter, I agree that it is important to get electronic ballast. I think both of these are, but I seem to remember someone saying that not all ballasts are equal, and I was hoping to have someone explain the difference and how it relates to the time of exposure.

  4. #4

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    Quote Originally Posted by Patrick Kolb View Post
    Thanks Peter, I agree that it is important to get electronic ballast. I think both of these are, but I seem to remember someone saying that not all ballasts are equal, and I was hoping to have someone explain the difference and how it relates to the time of exposure.
    The ballast factor is defined as the lumens a particular lamp will produce when operated by a specific ballast. It is a percentage of th total lumens possible. A ballast with a ballast factor of 95 percent should produce about 95 percent of a compatible lamp's rated lumens. For example, if a specific tube is rated at 3000 it will produce 2850 lumens with a ballast that has a factor of 95. So, yes, if two ballasts are compatible with a given tube the one with the higher ballast factor will produce the most lumens. And more lumens should result in faster printing times.

    Please note that the ballast must be correctly sized for the tubes and using the wrong size ballast may result in excessive current flow, with overheating. I am not familiar with the specific ballast you mention but someone at the store should be able to tell you which ballast is compatible with which tubes.

    Sandy King
    Last edited by sanking; 11-05-2006 at 11:31 PM. Click to view previous post history.

  5. #5

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    Thank you Sandy. It seems that as the ballast factor increases so does the price. Is there a point of diminishing return, where the increase in the factor does not effect the printing times that much?

    Also, anyone have any suggestions as to what ballast to use with the tubes mentioned?

  6. #6
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    Quote Originally Posted by Patrick Kolb View Post
    Thanks Peter, I agree that it is important to get electronic ballast. I think both of these are, but I seem to remember someone saying that not all ballasts are equal, and I was hoping to have someone explain the difference and how it relates to the time of exposure.
    Patrick - I have worked for my family's electrical supply business for over 30 years and I am familiar with the 2 ballasts you are interested in. Those 2 catalog numbers you mention are made by a company called Advance. We are a distributor for both Advance as well as a company called Universal. Those ballasts you mention are both magnetic and are designed to operate 2 F20T12 lamps. Neither company lists an electronic ballast for that lamp configuration. I'm sure it has to do with the fact that the 2 foot T12 lamp is no longer widely used except for specialty applications. Sandy King's explanation about ballast factor and light output is right on the money. Regarding cost - the RL series is worth about 35.00 and the HM series about 45.00. In theory, the light output difference is approx 30%, so you need to decide if the cost difference is worth it. Be aware however, that real life measurements do not always exactly coincide with the specs the manufacturer lists. Please also be aware that the case size on the RL series is 6-1/2" and the HM series is 9-1/2". One other difference is that the HM series is designed to operate down to 10 deg. F and the RL series is designed to 50 deg. F. - this is probably of no consequence for your application.
    Climbabout
    Tim Jones

  7. #7

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    Patrick,

    Most electronic ballasts have higher ballast factor values than both of these (although the .85 BF is near the range and could be electronic). If there is a substantial difference in price, my guess is the difference is due to one being electronic.

    We are making an assumption (which is pretty solid) that the UV output increases in the same manner as visible light output. With that regard, the higher the BF, the 'faster' the lamps will be.

    If you can provide more information on the ballasts, I can see what information I have in my literature.

    ---Michael
    www.mutmansky.com
    B&W photography in Silver, Palladium, and gum bichromate.

  8. #8

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    I just saw Tim's post. The difference in price is due to the low temperature rating...

    I figured neither of these are electronic, because the BF is too low for a typical electronic ballast.

    You may not have a lot of choices for electronic ballasts, but I think there may be one or two that are designed for 48" lamps that will also drive the 24" lamps. Actually, they will be over-driven, increasing the BF a bit to speed up the printing.

    Let me see what I can find.


    ---Michael
    www.mutmansky.com
    B&W photography in Silver, Palladium, and gum bichromate.

  9. #9

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    Thank you Tim and Michael, this is just the information I was hoping to get. I look forward to any suggestions you may have.

  10. #10

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    Patrick,

    Boy, looking over my literature here, it sure does seem like there are almost no ballast options left in the T12 lamps. The technology has moved on, and the T12 lamps that are left are all specialty lamps in one way or another. I suspect it is not a large enough market to make a good electronic ballast for them.

    I've got a call in about multipurpose ballasts. Some can be used for multiple lamp combinations, but the literature may not be entirely complete on the various compatibilities that they have.


    ---Michael
    www.mutmansky.com
    B&W photography in Silver, Palladium, and gum bichromate.

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