Why Do Some Fluorescent Lights Flicker While Others Don't?

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Discussion Overview

The discussion revolves around the phenomenon of flickering in fluorescent lights, specifically comparing two fixtures from the 1960s. Participants explore potential causes for the flickering observed in one fixture while another remains unaffected, considering factors such as bulb age, starter condition, and electrical characteristics.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant describes a fixture (F1) with two fluorescent lights (B1 and B2) that began to flicker, while another fixture (F2) with a single light (B3) did not flicker, raising a mystery about the cause.
  • Another participant suggests that the flickering could be caused by a life-expired starter and recommends replacing it.
  • A different participant notes that the flickering bulb may be aging, indicated by darkening near the ends of the glass, and questions whether the flickering occurs in phase or antiphase.
  • One participant confirms that the flickering is common and acknowledges the aging of the tube.
  • Another participant theorizes that the flickering may relate to the deteriorating emission of one of the aging filaments, suggesting that it could affect the light output during its half-cycle.
  • A suggestion is made to use a stroboscope to observe the behavior of the bulbs in relation to each other during flickering.

Areas of Agreement / Disagreement

Participants express various hypotheses regarding the causes of flickering, with no consensus reached on a single explanation. Multiple competing views and potential causes remain under discussion.

Contextual Notes

Participants mention the age of the bulbs and the condition of the starter, but there are unresolved assumptions regarding the electrical characteristics and interactions between the bulbs.

Buzz Bloom
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A Mystery re Fluorescent Lights

I have a fixture F1 from the 1960s with two 2' fluorescent lights B1 and B2. Recently they both began to flicker. A second fixture F2 has a single 2' light B3 which did not flicker.

In F2 I replaced B3 with B1. It did not flicker. I then replaced in F2 B1 with B2. It did flicker. I then in F1, put in B1 and B3. There was no flicker.

The Mystery: Apparently in F1 the bad bulb B2 not only flickered itself, it also caused the good F1 to flicker.
Has anyone an solution explaining this mystery?
 
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Possibly caused by a life expired starter . Try putting a new one in .
 
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The tube prone to flickering is getting on in years, is it? Near the ends of the glass is getting dark?

Could you notice whether the flickering pair were flickering in phase—or exactly in antiphase?
 
Buzz Bloom said:
A Mystery re Fluorescent Lights

I have a fixture F1 from the 1960s with two 2' fluorescent lights B1 and B2. Recently they both began to flicker. A second fixture F2 has a single 2' light B3 which did not flicker.

In F2 I replaced B3 with B1. It did not flicker. I then replaced in F2 B1 with B2. It did flicker. I then in F1, put in B1 and B3. There was no flicker.

The Mystery: Apparently in F1 the bad bulb B2 not only flickered itself, it also caused the good F1 to flicker.
Has anyone an solution explaining this mystery?
Yes, this is common.
 
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Hi NO:
Thanks for your questions.
NascentOxygen said:
The tube prone to flickering is getting on in years, is it?
Yes.
NascentOxygen said:
Near the ends of the glass is getting dark?
Yes.
NascentOxygen said:
Could you notice whether the flickering pair were flickering in phase—or exactly in antiphase?
The flickering was too fast to distinguish the relative phase.

Regards,
Buzz
 
The flickering is half your line frequency?

I think the origin lies in the deteriorating emission of one of the aging filaments. When it goes positive it needs to overcome a higher voltage to achieve conduction so ends up conducting less strongly or for less of its half-cycle making the light output lower on that polarity half-cycle. The darkening areas on the glass—that's metal that has evaporated off the electrodes.

You could probably fashion a simple stroboscope to determine whether the companion tube dims or brightens when the first dims.
 
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