Tech problem with MH light

[JasonH]

My 250w MH lamp keeps turning off. Basically, when the light goes on (either through the timer or manually) it stays on for a while, and then just goes off. Sometimes after being on for a few minutes, or up to around an hour.

 

I checked the line to the ceramic fixture with a voltage detector, and it's still getting current. At first I assumed the buld was bad, so I bought a new bulb - so it's not the bulb, because the new bulb and old bulb are both affected.

 

So, is it possible that the ballast is still sending current, but not enough current to fire the bulb - so the ballast is bad? It's an Ice Cap. I tried taking the cover off to see if there was anything I could see wrong inside, but it's covered with some kind of pour in rubber.

 

Or if the ballast is sending current, that's not the problem - meaning possibly the ceramic bulb-holder is bad? (I would be much happier about replacing a $15 fixture than a $120 ballast).

 

I appreciate any input.

[dsoz]

Is the ceramic charred in any way, like there may have been a bad connection between the bulb and socket? An open circuit may cause what you are describing.

 

dsoz

[finch6013]

sounds to me like a bad connection somewhere either in the socket or wiring. This could cause heat that will break the circuit in a bad connection. Then once the bulb turns off it has to cool in order for the balast to fire it again. Most balasts cant fire a hot bulb.

Check your connections, maybe change your wires,and socket.

[JasonH]

Thanks for the input gents.

 

The ceramic doesn't appear charred at all - everything seems in tact.

 

Checking connections...

 

Okay - basic question. I know that the ballast won't fire a hot bulb... but how does it know the bulb is hot? Is there some form of timer in the ballast?

[finch6013]

That I do not know. I think it just doesn't have the power. My balast will sound like its trying to fire the bulb but it just cant. The bulb will flicker sometimes.

[JasonH]

So, do you think the ballast is likely okay? It's definately sending electricity to the socket, even when the bulb is out. If the consensus is that the ballast is likely okay, I'll just get a new socket to see if that's the problem.

[JasonH]

well, I just tested the connections and fired it back up. It ran for 10 minutes and cut out. The bulb is hot, the ceramic is cool to the touch, and the ballast is mildly warm.

[JasonH]

Hmmm... fired it up again... and again went out at 10 minutes. That's a coincidence...

[JasonH]

3rd times a charm. Once again the light stayed on for 10 minutes. So now I'm thinking ballast. There is still power to the bulb, but the fact that the bulb zonks out after 10 minutes each time - seems more likely it's the ballast than the ceramic socket... right?

[Rick]

Open the ballast and try to see if there are any darkened areas near any connections that would indicate something is getting hotter than it should be. Does the wiring have any plugs between the ballast and the light? If so check that plug for corrosion and then use some dielectric grease (available at any auto parts store) in the plug. Also there are probably wire nuts conneting the socket to the wiring somewhere close to the socket. Take those connections apart checking for any dark or burnt areas and do the same thing with them when you put it back together (clean and use a little dielectric grease inside the connection).

 

I believe it is the bulb itself that will keep it from firing rather than the ballast. I can duplicate the same thing using a plain cap and core ballast (nothing more than a transformer and a capacitor). I.E. Once it is shut off it still has to cool before it will start again.

[JasonH]

Thanks, Rick. I've opened the ballast, but apparently Ice Cap fills their ballast with some kind of pour in rubber-type stuff that then hardens into a hard sticky goo. So, no luck in messing around with the guts. I did figure out that while power is coming in and going to/from the bulb, there is no power running back through the white wire back to the wall.

 

Being only a good enough electrician to recognize the smell of burnt hair, I'm not sure, but I think that's a bad sign. I think the circuit should be completing - in from the black wire and back through the white wire.

[Rick]

Thanks, Rick. I've opened the ballast, but apparently Ice Cap fills their ballast with some kind of pour in rubber-type stuff that then hardens into a hard sticky goo. So, no luck in messing around with the guts. I did figure out that while power is coming in and going to/from the bulb, there is no power running back through the white wire back to the wall.

 

Being only a good enough electrician to recognize the smell of burnt hair, I'm not sure, but I think that's a bad sign. I think the circuit should be completing - in from the black wire and back through the white wire.

 

Unless there is power through the bulb itself I don't think the common wire will get any power. I.E. When the bulb itself is hot and will not fire I don't think there will be power on it.

[Rick]

Also if you can find a different wall socket on a different circuit in the house and try plugging it in there to see if that changes anything.

[JasonH]

The bulbs downright chilly right now and it won't fire.

 

I get power coming into the ballast (black wire), to the socket, from the socket back to the ballast, but not from the balast back to the outlet (white wire).

 

Saddly, I think the ballast is fried. It's only about 5 years old.

 

Sad thing is, I have a 400w ballast sitting on the floor right now getting ready for a tank upgrade. But I think a 400w on a 29 gal tank would cook everything!

 

So, I'm going to shell out for a new 250w ballast that I'll need for less than 12 months. I love this hobby.

[Rick]

The bulbs downright chilly right now and it won't fire.

 

I get power coming into the ballast (black wire), to the socket, from the socket back to the ballast, but not from the balast back to the outlet (white wire).

 

Saddly, I think the ballast is fried. It's only about 5 years old.

 

Sad thing is, I have a 400w ballast sitting on the floor right now getting ready for a tank upgrade. But I think a 400w on a 29 gal tank would cook everything!

 

So, I'm going to shell out for a new 250w ballast that I'll need for less than 12 months. I love this hobby.

 

How tall is the 29g? If you can keep the tank from getting hot then I think it would work. I had one over my 40g (16" high) and the corals seemed to like it but the heat under the hood was too much for the tank.

[JasonH]

BTW, I was completely wrong about the "white wire theory". I tested the white wire when the bulb was firing and it's not getting current then, either.

 

But the light still dies right at 10 minutes. Seems like it has to be the ballast.

[dj_giantti]

What kind of bulb is it? I have seen that happen a lot with REEF GLOW bulbs. I would say you bulb is bad. Sometime the bulb will fire on and it turns off once it reaches it full heat. That usually take around 10 min for a bulb to reach full heat.

[JasonH]

That's what I assumed, too. I bought a new bulb and same thing - both XM, but the new one I just got today.

 

It could be the heat of the bulb affecting the socket, but there is no sign of wear on the socket, all connections are in tact - and it's such a simple mechanism. All sign point to the ballast being bad.

[chewie]

You have one of the old IC 250 electronic ballasts eh?

 

As you already know, the ballast is shot. It sounds like it may have overheated. The rubbery goo is called "potting".

 

Did you run the ballast with the aluminum heat sink?

 

Pick up a new style IC or a Galaxy ballast. When you upgrade, you can EASILY sell it for around $100 so it's only going to hurt a little.