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Where to buy cheap ballasts for old light table

Posted by Scarzi z7 MD (My Page) on
Thu, Feb 17, 05 at 15:19

If I can buy a complete 4' fixture from Home Depot for $7.50 I should be able to buy the ballast for less I would think.

Also, I have a real nice old light stand with lights that takes the standard 11" x 22" green plastic trays. The light fixtures are old with starters for F15T8 lamps. If I want to overpower these lamps what ballast could I use?

Follow-Up Postings:

RE: Where to buy cheap ballasts for old light table

Do the old light fixtures have old lamps? If so you'll need new lamps. My suggestion is to buy the $7.50 T8 fixtures and new t8 bulbs from HD and look up Zink's thread on overdriving.

RE: Where to buy cheap ballasts for old light table

If I use the Sun SL15 ballasts that come in the Commercial Electric fixtures from Home Depot, would one ballast overdrive two of the 15 watt F15T8 bulbs?

RE: Where to buy cheap ballasts for old light table

Yes, if the fixture holds 2 tubes.

The wires have to be paired as the diagram shows. The green wires on the right have to be added on.


RE: Where to buy cheap ballasts for old light table

  • Posted by zink 6a (My Page) on
    Sat, Feb 19, 05 at 22:08


The diagram by "Lightmaster J" shows you how to wire your 2 lamps in series. This wiring scheme will overdrive the two smaller lamps as if they were a single 48" lamp

I might point out one thing. In the diagram, on the left side of the upper tube, Lightmaster shows two pairs of red/blue wires. It may not be real obvious from this drawing, but one red/blue pair connects to one side of the socket(going to one lamp pin) and the other red/blue pair connects to the other side of the socket(going to the other lamp pin). The lower tube in the drawing has the red/blue pair shown a bit clearer.

Lightmaster J... I certainly don't mean to knock your drawing. Good job. It is correct and keeps me from having to draw it. Did you say you OD'ed a shorter set of lamps like this? I don't recall.

Scarzi... There will also be a GREEN wire (the ground wire) on the power cord. You should connect that wire to a metal part of the fixture. That will ground your fixture. The ground is not only for safety, but it also causes the metal reflector to act as a capacitive field, which helps to ionize the mercury/argon gas on startup.

Lightmaster correctly shows the wires between the 2 lamps, connecting the lamp-to-lamp pins, but you might want to use a different color than green. That is just to distinguish those wires from the GREEN ground wire. I use YELLOW myself.

Lightmaster does know what he is doing, as this diagram is correct. This is a great way to make a really bright, short fixture. Let us know how it went.

Again, good job Lightmaster! I still intend to do a more detailed drawing of this configuration with extra notes - if I ever find the time.


RE: Where to buy cheap ballasts for old light table


Yes I did use smaller tubes. I used 2, One foot T5 lamps and used a Sylvania Balast. I wrapped the wire around the pins and taped them and poof! Brightness!

I also tried some 6inch 4watt T5's that I pulled out of a broken Coleman Lantern. It worked too. All I need is to find some sockets. This will be fun....

There is also supposed to be a ground wire coming out of the ballast. This is the only brand I've seen that has one.


RE: Where to buy cheap ballasts for old light table

Hey, uh, Zink !

If you see this, I have a question, please.

Of the first set of SL-15's I have overdriven, one made a 'fizzzd' sound and quit working.

Is this common?

I was changing the tubes at the time: could that have been the problem?

I got out my tester and it seems that even a known good ballast has NO power output unless there's a florescent tube attached.

Is that what 'instant on' means ? I'm familiar with the idea of electronic supplies that only deliver when they sense the proper load...

So, is changing or adjusting a tube when the power's on a no-no ?

And while I'm only out $7.25 plus sales tax, is there a way to repair the damaged SL-15?

RE: Where to buy cheap ballasts for old light table

Thank you lightmaster and Zink! I can't wait to try this. The light table I have is so old that I'm sure it might have PCB's in the ballast. This will be great I can use the plant stand that accepts the standard green flats and have the added light from overdrivin 15watt bulbs in the fixtures with new ballasts. It is worth the investment in the $7.59 fixuters from Home depot to get the thing up and running. Thanks for your help and I'll let you know his it turns out.

RE: Where to buy cheap ballasts for old light table

Okay Jkirk3279,

The SL.15's have an End of Lamp Life Protection (EOLLP). When you change the tubes you have to turn the power off. A couple of mine will do that. Since you overdrove it, you may have the fixture incorrectly wired which causes a short and the EOLLP to kick in. When you turn it off, if the tubes are in, it may flash; that means it resetted itself.

Lightmaster J's Rules for Sl.15's
2. Make sure that tubes are in all the way.
3. Be sure that the wiring diagram is correct when you OD.


RE: Where to buy cheap ballasts for old light table

Well, thanks ! I replaced the ballast yesterday. I'll try putting it in a spare fixture to see if it comes back on.

I'm pretty sure it was wired correctly though. Must have been a line surge when I adjusted the tube.

I opened the ballast and there's no damage I can see or smell.

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