tube 'blackening'

[R.Lewis]

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I have noticed a major tube 'blackening' of a number of fittings using 28W
2D tubes with 'unbranded' HF ballasts.
The current crest factor is high - but what is the mechanism of the
blackening causedby this?

Regards



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[Al]

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I have noticed a major tube 'blackening' of a number of fittings using 28W
2D tubes with 'unbranded' HF ballasts.
The current crest factor is high - but what is the mechanism of the
blackening causedby this?

Regards

Possibly if the starter fails and the filaments glow all the time, the
tungsten will evaporate and coat the glass.

Al

 

[Robert Baer]

Possibly if the starter fails and the filaments glow all the time, the
tungsten will evaporate and coat the glass.

Al

Even CFLs have this problem.
One end is always closer to ground, and that appears to make the
current thru the tube non-symmetrical, so one end gets more "zapped"
than the other end, and the effect feeds on itself.