There are a few GE M250R2 Luminaires in the town I live in that are older ones.  I'd say these were probably manufactured around the late 1990s given the appearance, and the older NEMA labels (The new ones are bold printed, the older ones are not bold print), but there are 2 in my town that only work up to 40-60% of their rated brightness.  Is this a ballast problem, or capacitor problem?  There is also an AEL Durastar 30 Series that does the same thing.  It can't be the ignitor, as the lamps do start up, but they just don't work up to 100% of their brightness.  

How common is this among luminaires?  I've seen it in several luminaires throughout the years.  GE, AEL, Crouse-Hinds, Cooper.  Brand doesn't matter, but I don't see this happen in any of the MV luminaires that still exist, only the HPS.  Any answers?

I'd like to add that in my new M250R2, the Capacitor looks a little more rugged than the older one.  Is it possible that GE recognized this as a problem, and corrected it?

Wrong lamp i.e. 400W lamp on 250W gear, or failing capacitor



Its not the ballast. A brightness-changing failure would mean partially shorted ballast coil

1. If it changes by 40..60 % that mean the fault is allready progressed significantly, such ballast that won't last long before it goes out with a pyrotechnical show

2. A shorted coil would typically result in brightness going up.....



Its not the ignitor. The ignitor is a pulse device - It can't just stay there and partially short circuit, as if it does that continuously, it'll blow out very soon. Same as with the ballast, the fact that it's stable that way pretty uch rules out the ignitor

It could be either capacitor with lower capacitance (the "selfrecovery" feature had to act too often and so had eaten up significant amount of the active surface area), or with some ballast designs it may be the capacitor shorted (the inductive impedance is too high, as it is supposed to be subtracted from the capacitive one in a CWA system)

Or the ballasts are just marginal in the output current, so it may happen some lamps get stuck in some low temperature/pressure/voltage so transferred power state. It could be a result of too high voltage drop in AC input feeding cable.

I don't think that failure happens only with HPS and not with MV, the MV are just way less sensitive to that.

With the HPS even about 10,,20% ballast output current reduction may cause lumen drop more than 50%, just because the lamp is not able to heat up, so remains with lower pressure, so lower voltage drop state. The same happens, when you install higher wattage lamp into a lower wattage fixture...
The MV§s normally operate when all the MV is evaporated, so 10,,205 current reduction does not alter the arc voltage yet, so the output is just the 20% lower and that you most likely won't see.