EEVblog Electronics Community Forum
Electronics => Beginners => Topic started by: The_Almighty_Bacon_Lord on February 11, 2017, 11:10:20 pm
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Of all those components, the tubes are the most obviously life-limited (was the display already used for several years?) Over time the cathodes emission degrades. Since there is no heater, they then have difficulty lighting when cold, leading to flicker but not much light.
The inverter has switching transistors that could fail short; I don't know if the transformer often fails.
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Have a listen and a feel around the ends of the tubes. Sometimes the leads come off.
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Could also be HV breakdown starting to happen somewhere, but most likely aging tubes.
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If I recall ELO makes good touch screens. You could retrofit this to LED. Several hands-on examples exist on YTube:
https://www.youtube.com/results?search_query=CCFL+Backlight+conversion+to+LED (https://www.youtube.com/results?search_query=CCFL+Backlight+conversion+to+LED)
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I've never heard of "HV breakdown" before.
Partly because there are no heaters to pre-warm the cathodes, starting a CCFL takes high voltages, up to 3kV. That can be enough to blow through the insulation between the transformer windings. Since you can't see through the transformer, it's hard to detect this. The result would be that the output voltage doesn't rise high enough to start the lamp.
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A CCFL isn't "filled" with mercury: the amount is a few milligrams, and you would have to physically bend it for it to break. Inverters with a different design will have transformers with different properties; if the circuit doesn't resonate it simply won't work.
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My best advice is to never trust capacitors. Even if they are not bulged, they could still be far too degraded to do their job properly.