This might be 3 very stupid questions, I am sort of a beginner, but I have a new 400w MH ballast with a 400w MH bulb of unknown condition, but the discharge tube looked very clear when I bought it. I have 3 questions about them:

1: The lamp has no markings on it indicating the burning position. Does that mean it is universal burn?

2: The ballast is the constant wattage autotransformer type. If it is constant wattage, then shouldn't the power draw always be 400w even when the lamp is warming up? It only draws about 120 watts when it first turns on and never gets past 125w before cycling off. Is this normal?

3: Before I got a hold of a ballast for the lamp, I hooked the lamp up to a small high voltage cold-cathode driver just to see the mercury glow a little. I did this quite a bit, and I am worried that this could have damaged it. The discharge tube had some yellow stuff on it after a while on the CCFL driver, but when I first got it, it was clear. Could this be why the lamp is cycling?
Thank you for any help you can provide me!

do you have a picture of the 400W Metal halide lamp? the physical construction of the lamp should help us identify its specifics


the Constant-wattage name is a bit of a miss-leading name, those ballasts are actually constant current drivers, ie no matter the lamp voltage the lamp current will be the same, conversely however they are more resilient to swings in line voltage and are able to keep the lamp current constant even if the mains voltage goes up and down, and since the current is kept the same the lamp voltage wont change, hence the name "constant wattage" since even with relatively wide mains voltage flections it will be able to keep a fully warmed up lamps current constant and thus its wattage constant


but when a discharge lamp strikes its arc voltage is very low, thus given a constant current the lamp power will be quite low (as volts multiplied by amps = wattage) this is why lamps take longer to warm up on CWA ballasts then they do on Choke/HX ballasts



but I would make sure that your CWA ballast has its series capacitor in place and that said capacitor is not degraded, the capacitor of a CWA ballast is critical for proper functionality of that ballast type and if it begins to degrade, lose its capacitance then the lamp current will drop and the lamp wont warm up fully etc


driving a hot cathode discharge lamp off a CCFL ballast can and will indeed damage it but that is normally by way of electrode sputtering which you will notice by blackening of the arc tube especially around the electrodes, if the lamp's arc tube is still clear, then its likely still fine in that regard


hope this helps

Thank you so much for your quick response!
Thanks for the info about CWA, I didn't know that was why they were called constant wattage.

The ballast says it needs a 24 uF capacitor, the capacitor that came with it measures around 23.8 uF and is rated for the proper voltage, so that definitely isn't the problem.

Now that I look behind the white coating on the ends of the discharge tube, the inside of the tube is quite black near the electrodes, along with the yellow fog around the rest of the tube. You said that the black ends could have been caused by the CCFL driver. I only put the bulb on the CCFL driver for maybe 10 mins total, do you think this would have caused that much damage? I am now regretting not looking closely at the lamp when I first got it because maybe the black was there from the beginning, but I don't really know.

I don't have a picture of the lamp, but I can describe it in detail. It is a BT shape bulb, the etch is on the top, and the starting electrode is on the base side of the discharge tube. The discharge tube has the external white coating on both ends, which I think rules out the BU and BD burning positions. This narrows it down to horizontal, vertical, or universal to be possible options. I would think that if it doesn't have a burning position on the etch then that would mean it is universal, but I could be wrong.

If the CCFL driver really did mess it up that bad , is there any way I could possibly recover it? This is my only ballast and only lamp, and it would be cool to see it work.

Thanks again!  

The white coating has nothing to do with burning positions, it's purely a heat reflecting coating to raise the cold spot temperature behind the electrodes. The lamp will almost certainly be universal burning, but without a picture of it, it's not possible to say definitively.

 The white coating on both ends is typically universal burning . Here in the U.S. A base up only lamp has the coating only on the base end while on a base down only version it's only on the crown end of the arc-tube .

Are you sure you are using a proper ballast with a right open circuit voltage (metal halide vs mercury vs sodium) and wire it in a proper way, according to the schematics attached to the ballast?  A capacitor in an American syle ballast may be generally connected across the primary (a compensating capacitor in HX circuit) or in series with the lamp (CWA). Are you connecting a proper tap at a primary?

What arrangement are you using to measure the power? 120W certainly does not look right. Typically you see lamp runs up to almost full power (400W + ballast losses = almost 500W) before shutting off if it cycles.


Running an arc lamp on a CCFL inverter definitely should not kill it in 10 minutes, 5 milliamps current is too low and electrodes are quite robust, though that kind of idiocy certainly needs to be eradicated... In theory, that can release some free halogen impurities in the burner to temporary cause starting / running problems with the lamp, but I believe it will recover after aging for a few hours on a right ballast.
 

Would you be able to post pictures of your setup, including labels ? That would certainly help with troubleshooting (and I always like to see another MH setup, too !).

@ RRK - 'Idiocy' is a bit strong, isn't it..?

Are you sure you are using a proper ballast with a right open circuit voltage (metal halide vs mercury vs sodium) and wire it in a proper way, according to the schematics attached to the ballast?  A capacitor in an American syle ballast may be generally connected across the primary (a compensating capacitor in HX circuit) or in series with the lamp (CWA). Are you connecting a proper tap at a primary?

What arrangement are you using to measure the power? 120W certainly does not look right. Typically you see lamp runs up to almost full power (400W + ballast losses = almost 500W) before shutting off if it cycles.


Running an arc lamp on a CCFL inverter definitely should not kill it in 10 minutes, 5 milliamps current is too low and electrodes are quite robust, though that kind of idiocy certainly needs to be eradicated... In theory, that can release some free halogen impurities in the burner to temporary cause starting / running problems with the lamp, but I believe it will recover after aging for a few hours on a right ballast.

This is a CWA H-59 ballast that is wired properly according to the schematic on the label. The capacitor is in series with the lamp. It has many voltage taps, and I am using the orange 120v wire and feeding it 120v.

I am measuring the wattage with a cheap plug-in wattmeter that is of course on the primary side of the ballast. This means that the 120w power measurement is actually including the ballast losses.

What kind of ballast is the "right ballast" for aging? I totally agree that I was an idiot, I could've at least googled it before running it on a CCFL driver. Thanks for your help!

Sure you did not misspell the ballast ANSI code? For 400W MH a staple American ballast is M59, not H59. Though I may be not very proficient in American lamp gear, may be some colleagues will correct.

As for aging I meant an usual ballast prescribed for this lamp. If everything else is correct, and the lamp is just upset by running for some time with glow discharge, hopefully  it will restore its chemical balance and after a few cycles will start and run-up normally. If not I would suspect the lamp was already defective from the beginning and it was not running on CCFL inverter that damaged it.

I did misspell the code, it is in fact M-59 not H-59

The white coating has nothing to do with burning positions, it's purely a heat reflecting coating to raise the cold spot temperature behind the electrodes. The lamp will almost certainly be universal burning, but without a picture of it, it's not possible to say definitively.

thats very misleading, the white coating, has *everything* to do with the burning position of a metal halide lamp


I recommend giving these uploads by Max a read as to the importance of the white coating, and its influence on the burning position/thermal properties of a metal halide arc tube


https://www.lighting-gallery.net/gallery/displayimage.php?pos=-154383

https://www.lighting-gallery.net/gallery/displayimage.php?pos=-154318



please dont be so misleading to a new member like that who might not know better.




as for the OP, running the lamp for 10 minutes on a CCFL ballast, as RRK says thats fine, 10 minutes I doubt would of likely done it any harm


the ballast capacitor sounds good to me, 24uF is correct, have you double checked the voltage taps on the ballast? a lot of these US ballasts have multiple voltage taps, so I wonder if your perhaps accidentally have it on the 208V or 240V tap or such like?

for example doing a very quick ebay search I see while Venture have Orange as the 120V tap, for "Universal" branded ballasts Orange is 208V, so I would double check




also on the lamp front, have you tried operating it in different positions, or in the brief time it is working, to tap the bulb? does that cause it to go out or such? with this im trying to work if there is a bad contact thats acting like  a bimetallic switch as the lamp warms up

The white coating on both ends is typically universal burning . Here in the U.S. A base up only lamp has the coating only on the base end while on a base down only version it's only on the crown end of the arc-tube .

I think you have that inverted, a position redistricted metal halide lamp will *generally* (but not always looking at you GE Halarc!) have its white coated arc tube end at the lowest point in the lamp



for example note in the Lamp from Max that I Linked to,

https://www.lighting-gallery.net/gallery/displayimage.php?pos=-154383

its burning position is base up only, and notice how the white part of the arc tube is in the crown end of the lamp, as when the lamp is base up that is the lowest point in the lamp


and conversely on this base down burning lamp https://www.lighting-gallery.net/gallery/displayimage.php?pos=-230971

note how the white part of the arc tube is now near the base of the lamp since when burning base down, that is the lowest point of the arc tube



the whole point of the coating is to raise the temperature of the coldest part of the arc tube and ensure thermal uniformity of the arc tube for most optimal performance, and to simplify it, as most of us know heat rises, so thus the lowest part of the arc tube is what needs the most insulation




also with regards to the first line, certain lamps for horizontal burning only will still have heat reflective coatings on both ends of the arc tube, just something to be aware of


so the heat reflective coatings of a metal halide arc tube, can give you a good hint as to the burning position of the lamp, but one should still be on their toes about it if that makes sense

 You are correct !! The dumb thing is that I had it correct initially and reversed it !!

Thank you all for your replies! I am new here and I am just discovering how helpful the community here is.