Re: HID EOL lamp cycling - mechanism?

>   As for metal halide:  I suspect two things:
> 
> 1.  The arc tube gradually blackens and gets hotter, vaporizing more of 
> the halides (which there is normally a surplus of).
> 
> 2.  Some halogen from the halides corrodes the electrodes, making them 
> less efficient and that increases the arc voltage, as well as arc tube 
> heating which increases vaporization of halides and you get more arc 
> voltage and more extreme arc "negative dynamic resistance".
> 
> 2a.  Corrosion chops an electrode from its lead, and the arc has increased 
> voltage drop along with adding extra heat to one end of the arc tube.  I 
> suspect this is how some aging metal halides that are supposed to have 
> color temperature near 4000K or in the 4,000's K turn pink in color - 
> anyone please correct me here?  I do see some metal halides of color 
> temperature in the low (maybe mid) 4,000's K somewhat suddenly have a 
> color change from white to pink, and they usually completely conk out a 
> couple weeks to a few weeks afterwards.  I don't see them cycling, but 
> maybe with a different ballast they may cycle.
> 
>   I see cycling mainly with HPS, hardly ever with other HID lamps.  Most 
> cycling that I see with non-HPS HID lamps involves either lamps that are 
> failed and cycling before full warmup, or having clues that indicate 
> excessive voltage drop in the wires feeding them or something else wrong 
> such as lamp (bulb) / ballast mismatch or damaged ballasts or 
> (less frequently) ballasts incorrectly wired (wrong voltage tap used or 
> improper use/nonuse of a capacitor that is intended to be in series with 
> the lamp socket).
> 
>  - Don Klipstein ([EMAIL PROTECTED])

I've noticed that pulse start MH lamps will sometimes cycle at EOL, as
I've found out with an old 100w MH lamp and seen at a gym with 400w MH
pulst start lamps.