100w SON poor life span?

[Danny]

Does anyone here know why the 100w SON T lamps have such a poor life span? In some cases 2-3 years but 4-5 maximum? The 50w is the same too but slightly better i. Some cases with like 2-5 years and 6 max as ive got 2013 Philips 50w Cyclers? The life time of the 50w seems to vary quite alot, when the other wattages seem to do like 7-8 years some cases 12 years like an osram i was given had done? The 70w and 150w SONs seem to have a really impressive life! ???

[Kev]

I reckon those 50s you have that are cycling had been run on 70W gear mate

[James]

It's mainly just down to popularity of the different types. The lamps which run in the biggest volumes are those for which there is the most test data and the manufacturers put the most work into optimising. The 100W rating is not especially common and kind of gets left to the bottom of the list when it comes to making continuous improvements.

50W is technically difficult due to the small diameter of the arc tube, 35W is even tougher, so as a general rule the low wattage lamps always have inferior life vs the larger versions. Since 70W runs in big volumes though, a lot of effort goes into optimising the design of that one which is why in many cases it outperforms the larger 100W rating.

[amtrakuk]

That makes sense James. Why bother continual improving lamps that sell in small volumes and are prob loss leaders. They will put all the development into the lamps that sell the most. Maybe why the quality in SOX lamps are falling due to LPS will slowly be phased out.