I have a 400w MH lamp that is cycling. The ballast isn't the problem, and the capacitor is also not the problem. I now know that it is definitely the lamp. When I first bought the lamp, there was a large drop of mercury inside, and from what I have read, that means that it was a very new lamp. Once I put the lamp on a CCFL driver for an extended period of time (~10 mins), the electrode ends of the discharge tube were very black. The lamp also has some sort of a yellow deposit on the discharge tube, I can't tell if it is inside or outside the tube. The tube also has some white deposits that are definitely on the outside wall of the discharge tube, but these are not a part of the heat reflective coating. I am beginning to think that this lamp is unsalvageable, but I need some advice.

1: If there are white deposits on the outside of the discharge tube, does that mean that the outer envelope is no longer in vacuum? It doesn't have a getter so I can't tell by looking at that.

2: I can't tell if the yellow deposits are on the inside or the outside of the discharge tube. What would it mean if it were on the inside? What would it mean if it was on the outside?

3: Is there any way at all of recovering this lamp? Would temporarily overballasting it fix the black ends?
I am very disappointed in myself now that I know that I am the one who ruined this lamp, if you have any ideas at all please let me know. Thank you for any help you can provide!

Hi there, and welcome to Lighting-Gallery!

First and foremost, I'd like to ask if you know the make of your lamp, and whether or not it is a recent vs. NOS manufacture.

I've had weird discoloration with 90s Philips MH lamp after a first run-up before, but typically I've run the lamp for about five hours and it all cleared up.

Another thing I noticed is that older Sylvania lamps (particularly Mercury Vapor) tend to form white deposits (from what I presume is air/impurities). This too could have affected your particular Metal Halide make, if it is indeed Sylvania and an older one at that. (Saying this as they were likely made on the same machinery with similar processes).

Since your cap and ballast are fine, I'd probably think the lamp suffered some kind of premature failure? Maybe defective from the factory even? I would doubt that running this lamp for a measly 10min on a CCFL power supply would do much... though of course I could be wrong.

Wishing you all the best, and welcome to the club! 

-Maxim

Additionally, I believe you should be able to attach a file (or multiple) just below the text box. That would be much more helpful than descriptions alone. 

Posting a picture of the lamp in question will help immensely!

BTW, 400W probe start MH lamps are not that rare and expensive. Maybe the way is just to get another one and relax


Yellow deposits are certainly on the inside of the burner, these are iodide salts themselves. White matter on the outside is heat-reflective coating, and also some white stains are actually from the manufacturing. Quartz has very high melting point, very hot oxygen-hydrogen fires are used in the processing, and at that temperature some quartz get evaporated. It forms white stains when condenses on the colder tube parts nearby.

Thanks for the info about the white stuff on the outside of the discharge tube! I didn't know that this was a normal thing.

The etch is barely visible in many parts but I believe the brand is Diazo. Never heard of it, maybe someone can enlighten me.
Here is a picture of the lamp and the ballast label, hope it helps: (white circle behind lamp is just a stand so the bulb doesn't roll away)

Some 'Diazo' in the lamp name may point to UVA/blue special application lamp. Are sure this one is really rated 400W/M59?

On your photo some black sputtering can be noted, but it looks pretty minor. Really well-aged MH lamp often have burners looking completely black, but still start and run-up properly. AFAIK, tungsten electrodes in MH lamps are made from solid tungsten, often thoriated in the volume for activation. That kind of electrodes is very robust and hard to kill.

I just did some research, and as it turns out, this lamp in fact is a blue/UVA lamp. It is for developing certain types of photos I believe. They are meant to be operated on a normal m-59 CWA ballast, but with a slightly larger capacitor! I just tried it out to make sure and it worked perfectly and didn't cycle. I added a 5 uF motor run capacitor in parallel to the existing capacitor. From what I could find, the wavelength emitted by this lamp is not super harmful, but I am definitely not just going to use it for general illumination applications. From my research, the actual running wattage of this lamp is 500w, but only for short periods of time, just to develop a photo. Their lifespan is not super long either. I could only find 1 reference to this lamp on Lighting-Gallery, so it must be at least a little rare. Thank you so much RRK and Maxim, I wouldn't have figured this out without you.
 

Thanks!