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Florescent Light Ballast ?

Discussion in 'General Electronics' started by Lawrence James, Oct 26, 2003.

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  1. The ballast in an old fixture quit. It was the old style with a starter.
    Could not find a replacement ballast so I got a self starting ballast to
    replace it. Connected it up per the schematic on the new ballast. Light
    comes on but it is only about half as bright as a second fixture that still
    has an old ballast and starter. Whats up with this? Anything I can do to
    make it work right with the self starting ballast? Thanks in advance :)
  2. Please post again with the lamp/bulb dimensions, nominal wattage and
    markings, along with markings on the old ballast and the new one.

    Slight chance that the replacement ballast is of the "trigger start"
    type (a variation of "rapid start" that is used with "preheat"
    lamps/bulbs). In this case, be sure you follow the wiring diagram on the
    ballast (more reputable ones have a wiring diagram on the ballast, and so
    do some of the junkers). The wiring is different between "trigger start"
    and "preheat", and it's different beyond just eliminating the starter.

    Some "trigger start" ballasts are junkers. You may be better off
    getting a replacement 2-lead ballast for a preheat system, probably
    available at many hardware stores and maybe at home centers, and at some
    electrical and electrical/lighting supply shops.

    Please read: (by Sam G, also available elsewhere)

    - Don Klipstein (,
  3. Terry

    Terry Guest

    Several times have modified 'old style' (with starters) two X 40
    watt lamp fluorescent fixtures, with success. Wiring is colour
    coded so it was pretty straightforward, although had to extend
    wiring inside the fixtures because the used (i.e. second hand)
    modern ballasts available to me had wires that had been cut-off
    during removal for their replacement by 'electronic ballasts'
    (whatever they are?).
    Suggest: make sure the 'new' ballast is the correct type and/or
    the fluorescent tubes are OK. Is the fixture grounded; that
    sometimes helps. Terry.
  4. It is easier to get good ballasts for 40 watt than for 20 watt, since 40
    watt is so much more in use (mainly in commercial and institutional
    buildings more than homes). Of course, there are some junky ballasts also
    for the 4-footers. Some of those junkers are referred to as "residential
    grade" by some people - what to do is go to one of those electrical supply
    shops or electrical/lighting supply shops that contractors go to, wait
    patiently maybe 15 minutes at the counter for your turn and ask for a
    "commercial grade" ballast for (whatever - probably a 2-lamp F40 rapid
    start system if you have 4-foot by 1.5 inch diameter bulbs/lamps).
    If you need a good ballast for 2-foot bulbs, things are not as good and
    these are the options:

    1. Use "preheat" ballasts and starters. The usual 2-lead preheat
    ballasts for 20 watt 2-footers tend to be made compatible also with 15
    watt bulbs/lamps and although they will reliably make F20T12 20 watt
    2-footers work, they deliver only about 16, maybe 17 watts to them.

    2. Try your luck with "trigger start" ballasts. I see enough of them
    that appear to be of marginal design, sometimes acting "cranky" with brand
    new bulbs (lamps) of some brands.

    3. Convert to F17T8 (17 watt 2-footer that is 1 inch in diameter) and its
    ballast, preferably an electronic one. Those tend to work better and more
    efficiently than all too many clunkers of older technology (for
    2-footers). But bulbs (lamps) of F17T8 type are uncommon enough to
    generally be unavailable at hardware stores and home centers. Electrical
    and electrical/lighting supply shops often have them, but sometimes have
    to special-order them and may impose a minimum order of 1 case of them (25
    of them!).

    Also consider color codes of the 2-foot 17 watt (F17T8) and 4-foot 34
    watt (F34T8 or Sylvanioa FO32) bulbs/lamps:
    These come in a few different "color temperatures" (higher temperature
    is "cooler color") and 2 color-rendition-grades. The color code for these
    is typically within the part number and the part number typically looks
    like this: F(wattageT8)(grade)(colortemp.) or with Sylvania,
    The lower (but still better than old tech "cool white"/"warm white")
    grade is referred to as "7" (or Sylvania D7)(for color rendering index in
    the upper 70's) by brands other than GE and "SP" by GE. The higher grade
    is referred to as "8" (or Sylvania D8)(for color rendering index in the
    low-mid 80's) by brands other than GE and "SPX" by GE.
    As for color temperature: That portion of the color code is normally a
    2-digit abbreviation of the typically 4-digit "color temperature in
    degrees K". 30 is a "warm white" color that somewhat resembles
    incandescent. 35 is a "whiter warm white" that somewhat resembles whiter
    shades of halogen light or shorter life hot-running incandescent
    photoflood and projector lamps. 30 and 35 are generally good for home
    use. 41 is a white that looks like "cool white" but with better color
    rendering. 50 is an icy cold pure white that sometimes looks slightly
    bluish, although it approximates the color of noontime tropical sunlight.
    41 and 50 have some ability to look "dreary gray" unless you achieve
    "office-bright"/"classroom-bright" illumination levels around a thousand
    or a couple thousand lux.

    - Don Klipstein ()
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