MH Ballast problem??

[jtesdall]

I just plugged in my "new to me" dual 250W MH ballast with new 15K XM bulbs last night. It worked great for about 4 hours, then one bulb dimmed like it was just beginning to fire. The other bulb is burning just fine. This is all on the new (from ipiniowa) 90 I am setting up.

I have quick connects on the cords so I shut it down for about 15 minutes swapped the cables around and fired it up again. Then the other side won't fire. It glows but won't come all the way on. It also takes about 1-2 minutes to even start to glow.

I am assuming something has went bad in the ballast. Does this situation sound familiar to anyone? Hopefully the ballast has not gone bad on the first day of use, but this appears to be the case.

Also, my lights are about 18" above the water. Is this too high??

 

[Double-J]

Not sure about the ballast, sound like a bad one. I think 18" is too high from the tank with 250w lights on a 24" tall tank. I would try to go half that distance, of couse the spread is going to be visually less but it's going to have more of a punch at the bottom of the tank JMO

 

[jtesdall]

Thanks JJ.

Its actually a dual ballast, so 500W on a 90. Would you say 18" is still high? I love the working room.

 

[Double-J]

I say it is... If you could borrow someones par meter you could see how big of a difference it really is... might not be much at all but if you look at sanjays lighting article going form 6-12" is a significant difference. I suppose it all comes down to how the corals react and look to the light if they are happy at 18" well there ya go.

 

[jbrunken]

<a href=showthread.php?s=&postid=10692454#post10692454 target=_blank>Originally posted</a> by tinytool
Not sure about the ballast, sound like a bad one. I think 18" is too high from the tank with 250w lights on a 24" tall tank. I would try to go half that distance, of couse the spread is going to be visually less but it's going to have more of a punch at the bottom of the tank JMO

This is something that I've been thinking about a lot and I wish there was some information out there regarding how much of the light is absorbed by air vs how much is absorbed by water.

I would guess that lights intensity is degraded much more quickly in water than air, this would lead me to believe that raising the lights higher would lower the angle and thus the distance that light had to travel through the water to reach the coral.

In other words, if raising the light 3 inches vertically mean that the light had to travel 3 inches more through air and 1/2 inch less (horizontally) through the water.

I'm sure I'm missing something here, but it would seem to stand to reason...

-JB

 

[Double-J]

Sone and I played with his par meter and we measure the par with in the water and then pulled my lights back and measured and they were roughly the same readings. I would have expected that the water would have cut down on the par a lot more than what it did.

 

[jtesdall]

I found the problem. Burned capacitor, $26 at hellolights.

Anyone know what might cause this to happen? I don't want buy a new one just to have it go bad again. Hopefully that is just what happens sometimes like anything else, it just goes bad.

 

[SnkyJake]

Hey Joel, how did you find out is was burned capacitor? I ask because I have one ballast that just started doing the same thing.

So I'm wondering if I can take it to electrician or someplace local and save myself the bucks of having to buy a new ballast.

 

[jtesdall]

It was pretty easy actually. I opened the case and one of the capacitors was bubbled out on the top and side. From experience I know capacitors do this when they burn up.

I also took and swapped the capacitors from one transformer to the other. I just snipped the leads and reconnected each to the opposite transformer since this is a dual ballast. Sure enough the opposite bulb wouldn't work so I know it is the capacitor. I also posted on the RC lighting forum to help me with this conclusion.

I was looking on line and the capacitor was priced anywhere from 60-200. Then someone told me to look at hellolights and whallah, $27 so the order gets placed tonight. Luckily my aquarium is just cycling so I can avoid the overnight charges.

I am happy to help further if I can just ask away.