How do you tell if a ballast is shot?

[scolley]

I've got a Pentair 25w UV (which I would not recommend to anyone BTW) that no longer lights. Since it stopped working about 2 yrs after I started using it, I assumed my bulb was shot... I only run it a couple of hours a day though.

So I pulled a spare bulb, plugged it in, and it does not light. So I took a continuity tester to both pairs of terminals on the bulb (1 pair for each end) and I get positive confirmation of continuity on each end. So the filaments appear to be intact, and I'm assuming the bulb is good even if it won't light.

Now I've got to suspect the ballast. But it would be really lame if it burned out after around 1500 hours use, or 700 ignitions.

Does anyone know how to check the ballast, when I don't have any "confirmed" good 25w UV lams laying about?

Thanks in advance.

[dbosman@msu.edu]

No, but either the ballast or a connection is shot since the bulb probably isn't. I say probably as it may pass continuity but still might not light.

First, if you don't mind opening things up, since you have a continuity checker I think the answer is you don't, check the wiring and connections. Redo any suspect connections. If they are good, the ballast is all that's left. Check online or your local electrical supply house for a ballast. Check multiple locations as prices vary way too much.

[scolley]

Thanks. Your recommendation would typically be pretty solid, but in my case I doubt that wiring check is needed. Those wires have not moved an iota since they were installed. I've got about the most nailed down - every wire secured - every pipe hard harnessed - stand you can imagine. Tis wire is so tightly mounted to the stand, I'm sure it hasn't moved at all. So if that wiring is bad, it's a case of spontaneous wiring failure, not because it was getting any stress, because that wire has had none.

Which I suppose is possible. But I'd rather know how to check the ballast. If I'm gonna have to go disconnecting things that are bolted in (it is NOT a easy thing getting this ballast and wiring out of the stand and then putting it back), I'm happy to check the wiring, but not if I can't the ballast while I'm at it.

[dbosman@msu.edu]

Wire connections fail, usually due to oxidation or more properly breaking the oxidation.

Since you have eliminated the bulb and the wiring, the only thing left is the ballast.

[scolley]

No, not at all.

As you indicated, my elimination of the bulb may not be accurate. Just because it passed a continuity test does not mean that it is "good", that it will light.

As you've indicated, apparently wire can fail without being stressed. So I can't conclude my wire is good either.

But I don't want to buy a new bulb, just to test to see if it's something else. And I don't want to get at the wiring (due to the difficulty) if I'm not going to test the ballast too. So that leads me right back to my original question...


Does anyone know how to test a ballast?

[zenfish]

BALLASTS are high voltage,and I do not believe you can test them with normal"VOLTOMETER" testing equipment.

The first step is to get a new light and see if it works,if it does not work,then it may be wiring.

One sign I have seen for a bad ballast,and I just recently replaced the one on my coralife,is the light will "FLASH" for a second then nothing..If your light does that,then it is the ballast,if it does not flash,or anything,it COULD be the bulb,but probably the ballast.

So you are back to the first step..Get a NEW BULB and try it.

[dbosman@msu.edu]

Ok, Here is the process from Advance Transformer. They ought to know.
http://www.advancetransformer.com/up...ng-guide-2.pdf

Tools needed:

True RMS Voltmeter
Ranges: 0-300-1000 Volts AC
Ammeter (clamp-on type acceptable)
Ranges: 0-10 Amperes AC
Multi-meter (with voltage and current ratings as shown above)
Frequency: 60Hz for electromagnetic, above 20kHz for
electronic

[scolley]

Cool. Thanks!

I'm gonna test, and THEN spring for the new bulb.

Thanks again!

[susankat]

I had an electrician tell me you can tell by the smell, if it smells like its been burnt its bad.

[confuted]

Originally Posted by susankat

I had an electrician tell me you can tell by the smell, if it smells like its been burnt its bad.

Of course, but it's also possible that it burned up and no longer smells, or failed without any sort of short. Sufficient, but not necessary.

[jeff@zina.com]

Originally Posted by susankat

I had an electrician tell me you can tell by the smell, if it smells like its been burnt its bad.

Oh those crazy electricians...

Of course, if it's currently on fire or the lamp has melted into the tank it's probably also bad. But I've had bad ballasts without any smell. The obvious solution is to use only a single brand and size of light fixture for every tank, then it would make sense to have a spare ballast.

FWIW, bulbs fail, ballasts fail and for those that have them, starters fail. Almost never does wiring or socket fail without visible damage, corrosion, cracking, etc. Ruling out the bulb almost guarantees the ballast.

Jeff

[susankat]

Originally Posted by confuted

Of course, but it's also possible that it burned up and no longer smells, or failed without any sort of short. Sufficient, but not necessary.

He is working on one for me that was given to me, the ballast has been gone for more than 6 months and it still smells. I can vouch for that one.

[bsmith]

QFT

I just had this happen to me. You would turn the switch on and the bottom of the bulb (closest to the power connection) would flash then quickly go out.

Originally Posted by zenfish

BALLASTS are high voltage,and I do not believe you can test them with normal"VOLTOMETER" testing equipment.

The first step is to get a new light and see if it works,if it does not work,then it may be wiring.

One sign I have seen for a bad ballast,and I just recently replaced the one on my coralife,is the light will "FLASH" for a second then nothing..If your light does that,then it is the ballast,if it does not flash,or anything,it COULD be the bulb,but probably the ballast.

So you are back to the first step..Get a NEW BULB and try it.

[airborne_r6]

As an electrician I have never tested a ballast. I put in a new bulb then check the voltage of the wires supplying the ballast where they connect to the ballast wires then I ensure that their connection is good. If I have done that its the ballast. There is only three things that can go wrong, the bulb, the wiring or the ballast and if the bulb and wiring are good it has to be the ballast.

I have seen plenty of ballasts come bad from the factory or burn out in a few weeks so the time really has nothing to do with it.

[scolley]

Originally Posted by airborne_r6

There is only three things that can go wrong, the bulb, the wiring or the ballast and if the bulb and wiring are good it has to be the ballast.

Thanks. It was the ballast.

I checked wiring continuity. That was fine.

I bought a new bulb an plugged it in. It did not light.

So I bought a new ballast, and the new bulb worked. And so did the old one.

No surprises here. Problem solved. No ballast testing required.

Thanks for the help.