# How do I check a ballast?



## MacGyver

Hi
Does anyone have a link to decent instructions on how to check 4ft & 8ft fluorescent ballasts?
Or explain it in a few easy steps?
I found a few references searching google, but nothing good.
I have an old 8ft 2 tube fixture that I believe just expired.
TIA for any help & suggestions /ubbthreads/images/graemlins/cool.gif

I was also going to ask where I could find a lumen comparison chart of different fluorescent tubes, but my searching just turned up this pdf, if the link works: GE PDF file
38 pages of nice reference material for light reading (stupid pun semi-intentional...) /ubbthreads/images/graemlins/popcorn.gif


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## jtr1962

Usually the best way is to just put known good tubes in the ballast and see if they light. I know it's obvious, but anything you could do with test instruments such as a multimeter won't simulate the ballast running under load. A bad ballast might give a good reading for open circuit voltage, but the volage might sag under load too much to drive a tube.

Also, if electronic replacements are available, it's a good idea to replace your old magnetic ballasts with electronic ones. I did so in several 25+ year old fixtures even though the magnetic ballasts still worked. The electronic ballasts save energy, usually the tubes are a little brighter, they buzz less or not at all, the other tube(s) stay lit when one goes out, and there is no more 120 Hz flicker. I also figured since the ballasts were so old, it was probably only a matter of time before they went.


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## Zelandeth

Here's a useful page for troubleshooting.

Don Klipstein's Light Site - Flourescent lamps page, troubleshooting section.


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## InFlux

I second the recomendation to switch to electronic ballasts. 

You can probably get a whole new fixture for just a few bucks bucks more, and it will have all the advantages JTR mentioned above- plus work better in cold weather.

The old T-12 magnetic fixtures are quickly being phased out.


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## MacGyver

Thank you for the suggestions, and the usefull link.

I tried new tubes right away and no joy.
A little history:
First tube went out while I was in the garage, then second within an hour. I figured if it had been a bad bulb the second one wouldn't have failed right away too.

I actually have a spare 8' ballast I was hoping to test before I install it, but that doesn't take long anyway.
For some reason I also seem to have ended up with a collection of new 8' tubes too, or I'd just switch it out for a couple 4 footers. Figured I'd use up what I have.

I'll check into electronic ballasts too, but I'm suprised how well these old ones work in the winter here.
They're so old the power factor is quite low, so newer more efficient ones won't save me money /ubbthreads/images/graemlins/blush.gif


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