Bulb ratings and fittings

n at minus 100C!

There are 3 derating lines shown. How do you make sense of them?

NT

And it never does in his labs, not enough power. ;-)

Cheers, T i m

None of them seem to be applicable to the resistors shown. The spec says derate to zero at 250°C (from 70°C) but the 70°C derating curve in that graph has its zero point at 300°C!

However, there is a gentleman in New Delhi who should be able to answer your question if you wish to purue it - see the Contact Us page.

Why not give him a bell and report back?

They pretty well all use 105C, 5,000 or 10,000hr capacitors.

They often end up running hotter than this in enclosed fittings, which will reduce the life of this capacitor, but control gear failure is very rarely due to this capacitor failing (I've only seen one case, and it didn't stop the lamp working - just went dimmer). Early failure of control gear is more commonly one of the MOSFETs going pop.

Note that some control gear deliberately sacrifices itself when it detects the tube is worn out, to prevent it continuing to operate a dead tube as a cold cathode tube which (ironically) risks the tube overheating and setting light to something or the glass breaking. This is crude and relies on a fusible resistor burning out when the tube voltage and power consumption increase in cold cathode mode. (Reusable control gear detects this by noticing the tube turn into a partial rectifier when the emission coating is all gone from one end, and shuts down temporarily until the tube is replaced.)