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Old 02-26-2021, 09:52 AM   #1
ohren
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Default Lowering CCFL brightness increases blinking freq. -- what's that indicative of?

Say all CCFLs have started blinking in an LCD display, so that all of them go black momentarily every 3 seconds. For a typical CCFL controller circuit in such a display, what would be the likely reason that the frequency of blinking is higher the lower the brightness?

I.e. why would the interval between the blinks decrease with the brightness level? Is it characteristic of a failing bulb, a cap, or something else?

My electronics skill level is pretty novice. I understand the basics and have repaired a PSU with some guidance, but don't have enough intuition to make good use of the above information. For instance, I've gotten the impression that a CCFL controller will shut off all of them if one of them fails (?) but I still don't know at which timescale this process happens and whether that could possibly result in momentary blinking if one of the bulbs is just failing intermittently.

I did start a more specific thread about a particular display in that subforum, but didn't do a good job of attracting a reply and couldn't figure out how to edit the title to reflect new info, so I decided to ask a more general question about it here. Hope that's ok.
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Old 02-26-2021, 04:27 PM   #2
stj
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Default Re: Lowering CCFL brightness increases blinking freq. -- what's that indicative of?

worn tubes, or bad caps
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Old 03-03-2021, 04:43 PM   #3
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Default Re: Lowering CCFL brightness increases blinking freq. -- what's that indicative of?

Thanks for the input. With that in mind I inspected the tubes (no visible problems) and measured the 24 V going from the power supply to the inverter with a DMM. The voltage seems to drop in sync with the blinking.

Now to determine whether that is a cause or an effect of the lamps shutting off...
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