The Lamp Room

Posted: **Mon Apr 15, 2024 1:57 pm**

You meaning: When only one wire connected to each end of the lamp, it will run most EOL lamps to vacuum loss?

The ballast will require filament continuity at both ends of the lamp to sustain self-oscillation because they form part of the circuit. When one end burns out, the oscillator stalls. If you were to short out the open-circuit filament, the oscillator will work until something else fails. In a throw-away CFL, often a transistor fails short-circuit and blows the in-line fuse.

Posted: **Thu Jul 04, 2024 9:51 pm**

The ballast will require filament continuity at both ends of the lamp to sustain self-oscillation because they form part of the circuit. When one end burns out, the oscillator stalls. If you were to short out the open-circuit filament, the oscillator will work until something else fails. In a throw-away CFL, often a transistor fails short-circuit and blows the in-line fuse.

Some of the more advanced programmed start HF ballasts seem to be able to run their lamps with one or both ends of the tube having only one wire attached, I am guessing they use some different circuitry to these more basic ones? They still appear to work normally but of course just cold start the end with only one wire attached (or a broken cathode if that's the case)

The Lamp Room

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