Metal Halide bulb not firing

[Chad]

Likely culprits before I start tearing the ballast apart?

 

It's a magnetic ballast and a phoenix 14k lamp.

 

Thoughts?

[sachabballi reef]

new bulb?

[Coral Hind]

Did you plug it in? Have you tried swapping out the bulb? Does it try to light or flicker at all? With the power off, bend out the contact to make sure it connects with the bulb.

 

If you swap it out with a known good bulb and still doesn't light it is probably the capacitor that needs to be replaced.

[OldReefer]

Probably thought of this already, but make sure the center contact in the socket hasn't been bent back. That has made me crazy a couple times.

[Chad]

The bulb is only a couple weeks old, is getting power (fan powered directly from the bulb contacts turns on), does not flicker. One day it turned on, the next it didn't. The bulb looks good, but unfortunately I don't have a backup to try it with...

 

I'll take it apart and inspect the capacitor.

 

Thanks, y'all!

[Chad]

Nothing visually obvious in the ballast...

 

Interestingly, yesterday was the first day the lamp didn't come on. But looking at the graph of amperage, Sunday used 0.5 amps more than previous (3 amps for the ballast instead of 2.5 amps) and not the ballast pulls 1.25 amps when on. Odd.

[Chad]

So, I guess staring at this remarkably simple device, I guess it's either the cap or the lamp. Anyone know a consistent local source for a large cap?

[Coral Hind]

The cap can fail in different ways but if in a direct short it allows the bulb to become a run away with no amperage being limited so it will continue to rise until the ballast over heats and fails.

 

I would still try a different bulb and see what happens there. Does the ballast hum at all?

[Coral Hind]

Grainger is where I get my caps from, see if you have one close by. Any commerical lighting/electrical supply would have them.

[Coral Hind]

It could still be the bulb as a failing bulb will require more amps to sustain the arc so don't rush to replacing the cap/ballast until you try another bulb.

[sachabballi reef]

i know you don't have any other bulbs...I wish you were closer as I would run one by to you....if the snow passes by and I can get to the usps I would be happy to drop one in the mail for you to have ....

[Coral Hind]

Chad...If you remove the cap from the circuit does the lamp light?

 

The reactance of the cap acts like a current limiting resistor but it isn't needed to start the lamp. With it bypassed the lamp will light if the bulb and ballast are functioning. Just turn it off before the ballast/bulb over amp, within five minutes. If it does light then that lets you know the cap failed in the open causing the circuit to be incomplete.

[Chad]

Taking voltage across the cap is 0 when off and ~23 when on. The transformer lightly hums when on.

 

Thanks, I have a grainger near me that I'll visit tomorrow for the cap and see if someone locally has a lamp I can try.

[Chad]

Thank you, Jenn, I greatly appreciate it, but I will see if I can find one... I'll likely be able to. David, I'll try taking the cap out.

[Chad]

OK, I think it's the lamp.

 

The cap charges and discharges like I think it should after staring at the schematic and turning it on and off... That sucks, it's a practically new (only a couple weeks) old! grrr.

[Chad]

LOL. I'm driving myself nuts, sorry!

 

Now I'm not so sure it's the lamp. I'm only generating 5 Vac across the lamp when it starts up. I had bad contacts to get into the cap leads, so it's actually zero when off / 140 Vac when on. As far as I can tell, that's what I'm looking for.

 

How's this ignitor supposed to work?

[Coral Hind]

ignitor? Is this an HQI ballast because a normal one doesn't need an ignitor? Is the ANSI code viewable so I can be sure I know what you have. Yo never really stated wattage, SE or DE.

[Coral Hind]

Also, be careful testing for voltage as the starting lamp voltage, depending on your wattage of lamp, can be well over 1000v briefly.

[Chad]

It's a DE, HQI lamp. Sorry about that... It's a 250 HQI. The fixture was originally a coralife and the ballast still is.

 

Here's a pic of the ignitor, transformer, and cap... I went looking for the ignitor (and found it shoved in the corner of the fixture) when I saw it on the schematic.

 

 

 

[Coral Hind]

Well just looking at the ignitor tells me it is not ideal. A 250w DE needs an M80 and that ignitor is not classified for an M80. The cap is correct.

 

This is what I would do. Try a different bulb. If that bulb doesn't work replace the ignitor as a working ignitor should have flashed your meter with about 1000v. The ballast and cap are probably fine from looking at them and from what you have tested. Normally a failed cap will show bubbling.

[Coral Hind]

Chad, notice on the top right of the ignitor, the lightning bolt with 3.5-5kv. That is why I said be very careful testing for voltage. That thumps the bulb 3,500 to 5,000 volts!!

[Chad]

Huh. Another reason to despise this coralife pos.

 

I'm pulling half old knowledge that's probably broken, but the M80 is the full ballast (for high current bulbs), correct? As long as I have this thing apart, I'd really like to fix it the way it should be fixed. If the ignitor isn't the right one, I want to fix that.

 

I'll see if I can find a bulb for tomorrow to test the fixture, though.

[Chad]

LOL... yea, I noticed that... I suppose it's good I only got 5 volts... my meter is only good for 1kv!

[Coral Hind]

I'm not sure I understand the "high current" comment/question. The M80 is specific to the DE 250w "Probe" start bulb.

 

http://www.kolmart.com/HID-ANSI-Code-Guide_b_3.html

[Chad]

(ahh, broken knowledge )

 

You gotta love how a ballast that comes from the manufacturer isn't the one recommended.

 

OK, so the ballast is the transformer, cap, and ignitor? Should I just suck it up and replace the ballast parts?

 

Thanks for your help, David.