# Electronic CFL ballast running linear lamp?



## Zelandeth (Aug 16, 2004)

I bought a cheap "blacklight" fixture a while ago, running an F15T8BLB tube, unfortunately, it never worked properly from day one. Tubes would generally work fine for a week or so, then refuse to start after that, and the ballast seemed to run excessively hot, the lamp flickered a lot too. Eventually, I got fed up of buying tubes for it - and it just got ignored, as I was certain the ballast was to blame, and it was a £10 fixture.

Until that is, I dropped my poor innocent 15W Mercury 2700K compact fluorescent bulb last week, smashing the tube. Poor thing had sat in the same fixture for over two years without giving me trouble - and how do I repay it, dropping it.

Still...I had an idea, and salvaged the BC cap and the ballast PCB before I junked the rest. The BC cap went into the parts box, and the ballast got stuffed in a drawer.

Today, I took apart the blacklight unit, dumped the original ballast...is just a transformer...a small one at that...and wired in the one from the CFL. (obviously, having to modify the existing wiring, as there is no longer a requirement for the starter).

Powered it up, and after a few seconds of flickering, it lit up properly. Powering it up now doesn't even cause the flicker...and all the "dead" tubes now seem to work too!

So...a two year old £5 CFL ballast works fine...and the purpose built one doesn't.

Should this ballast be okay running this lamp? The power ratings are the same (15W), and it doesn't seem to get hot, but I wonder if the difference between the linear and triple-U tube will make any difference to it - though other than the diameter I can't see why.

Anyone else done this sucessfully?

(can post pics if anyone wants as well).


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## Zelandeth (Aug 16, 2004)

D'OH! Posted it in the wrong forum! Moderators/admins please feel free to move as appropriate...sorry! My mistake there.


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## brickbat (Aug 16, 2004)

I've tried this. I took the electronics out of a philips 18W "earth light" and used it to run a 15W T8 tube. It does work, but...

From what I have gathered small CFLs typically operate at a lower arc current than an old-style T8 tube. (Old T8s are rated at 430mA) Not having a current meter that was accurate at these frequencies, I can't make the measurements to prove it, but I can measure the AC input power and it's running less than 13W, so that seems to support me theory. Also, the bulb ran fine for about a year, then had to be replaced. As the bulb was used when I started, I can't say for sure that the CFL ballast was the cause, but it's possible, as I didn't check the filament drive levels - it may be over or under driving them - I just don't know. And again, I don't have a TRMS meter for these frequencies. 

The good news is that nothing catastrophically fails, it seems pretty efficient, doesn't get hot, and it's a super cheap way to get an electronic ballast. I'd say further experimentation ought to be encouraged! (still, to be on the safe side, make sure the ballast gets housed in a metal enclosure...just in case)


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## yuandrew (Aug 17, 2004)

I did this as well. I used a cheap chinese made 20 watt CFL (Top Lite brand)  . My mom happened to get several 20 watt spirals for free at a chinese store (T.S. Emporium). The lamp I modified was a 20 watt undercabinet light that used a 2 foot GE chroma 50. What I did was hacksaw the bulb open and unsolder the wires from the ballast circuit board. I modified the wireing in the undercabinet light so the "electronic ballast" drives the flourescent tube the same way as it drives the CFL. 120vac to the board input and 4 wires to the lamp (2 on each end). The circuit board almost fits perfectly into where the old magnetic ballast went (Ok,I had to bend a capicator sideways so it didn't hit the lid. Great improvement over the preheat ballast; no more (flip light switch, flick-flick-flick--flick--flick, light). Just (flip light switch, instant light).
The undercabinet lamp I used is now on the ceiling in my room and it lights the whole place up. I use it for general room lighting in a 13'x10' bedroom with a 10 foot ceiling. I still use a 100 watt table lamp for reading and task lighting but compare using a 20 watt flourescent vs a 200 watts of incandescent for general room lighting. 

I've posted this before in 2 other forums here on the CFLs page and on the
Full Spectrum page


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## yuandrew (Aug 17, 2004)

Here's the website I learned this from DIY electronic control gear


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## Wim Hertog (Aug 18, 2004)

I modded my aquarium light recently with a 20W CFL ballast. The original was a 15W magnetic style one. The bulb in the hood is an expensive 15W 5500K full spectrum tube with a CRI of 98 and a 7 phosphor mix. Measured AC input power of the ballast is 18.1 watt. The hood is running much cooler now. I hope the tube is happy as well. Seems to be just fine after 1 month, 12hrs a day. Normal life is about 12000hrs (after that it's too dim to use).


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## Wim Hertog (Aug 18, 2004)

Zelandeth, is it possible to host a few of pics and post them on CPF?


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## Zelandeth (Aug 18, 2004)

I'll have to go get the unit off the ceiling again, but sure, will post a few pics. Will edit this post with them once I've got the pics.


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