iMac RFI.. a test for a failing fluorescent inverter?

Post #344,159 by Ashton 6/24/11 4:22:32 PM Reply	iMac RFI.. a test for a failing fluorescent inverter? Noted (on my May-'08-spawned 2.66 GHz 20"): Max-brightness (as you could 'read by') is down just a tad since my acquisition in 1-'09--I only go here briefly, normal for me is 2-dots at night, maybe 4-dots daytime illumination. At MAX it's still way-too bright for any normal eyes to need, except maybe to win a pissing match. My off-air NPR appears to be an adequate hash-detector, and the static intensity --> Â(screen brightness). Not an issue first 1+ years here; began to notice a few months ago. [yes, on 'FM'.. or at least, scrambling something within the receiver electronics--such that output audio does get modulated] Doubt this occurs on LED backlights, etc. Anyone else observe the phenomenon? Maybe, too: this is the natural failure mode for all the plasma stuff that goes on in these 'bulbs' and not an indicator of the inverter packing it in, at all..
Post #344,167 by Another Scott 6/24/11 5:34:36 PM Reply	Dunno. My T61 laptop starts out dim after awakening from sleep and slowly gets brighter over a few minutes. I think it's the nature of the fluorescent tubes that they used before switching to LED backlights. I would think that if the inverter were seriously failing it would have a more dramatic effect on the image (e.g. going black after being on a few minutes). You might want to look around here to see if there are any possible pointers - http://www.ifixit.com/Browse/iMac_Intel - though nothing jumped out at me. The fluorescent tubes do require fairly high voltages to operate (something "fun" to do is get one of those "pens" that light up when put near an energized AC line. One I have lights up in several places when put near my T61's display bezel.) As the fluorescent tube characteristics change, it may be requiring higher voltages and different frequencies from the inverter circuit, giving rise to differences in the NPR static noise you're hearing. If I'm understanding you correctly. :-) Dunno if it's worth the trouble to do anything about it. Opening those boxes isn't for the faint of heart from the pictures at iFixit! HTH a little. Good luck! Cheers, Scott.
Post #344,630 by Ashton 7/7/11 6:40:49 PM Reply	Gracias ... belated Concur on the complexity and also--probable irrelevance; eg ... so wtf are ya gonna Do! about it? Lazy-person's reply: ¡Nada, Señor! Doubt that this Giant Notebook iMac can match the mtbf of the lowly eMachine and its 10-year run (with anemic PS and 600 MHz) Will just make periodic offerings to the ~~Death of All Rats~~ er, Cthulhu-of-all-Techno. Nothing has yet failed; I no worries. :-)

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