What fails in CCFL inverters?

Started by John E. April 26, 2009
What fails most commonly in inverter circuits in, for example, 18 inch LCD 
displays? 

<http://www.lcdrepair.us/1800inverterKUBNKM045A.html>

I know anything *can* fail. But is there a common, high-frequency failure 
component in these inverters?

Thanks.
-- 
John English

John E. wrote:
> What fails most commonly in inverter circuits in, for example, 18 inch LCD > displays? > > <http://www.lcdrepair.us/1800inverterKUBNKM045A.html> > > I know anything *can* fail. But is there a common, high-frequency failure > component in these inverters? > > Thanks.
In the inverter that I have replaced, I have seen the inductors burned up or open. So I would say that the inductor insulation got hot and shorted between windings. don
"John E."  wrote in message
news:0001HW.C6194C9E007788DCB02149AF@news.sf.sbcglobal.net...
> What fails most commonly in inverter circuits in, for example, 18 inch LCD > displays? > > <http://www.lcdrepair.us/1800inverterKUBNKM045A.html> > > I know anything *can* fail. But is there a common, high-frequency failure > component in these inverters?
The short between the turns of the transformer is a very common failure. VLV
On Apr 26, 8:26=A0am, John E.  wrote:
> What fails most commonly in inverter circuits in, for example, 18 inch LC=
D
> displays? > > <http://www.lcdrepair.us/1800inverterKUBNKM045A.html> > > I know anything *can* fail. But is there a common, high-frequency failure > component in these inverters? > > Thanks.
It is mostly the TV programs that fail.
> -- > John English
"John E."  wrote in message 
news:0001HW.C6194C9E007788DCB02149AF@news.sf.sbcglobal.net...
> What fails most commonly in inverter circuits in, for example, 18 inch LCD > displays? >
the same thing that fails in 15 inch LCD displays.
> It is mostly the TV programs that fail.
Very funny. I agree: My TV won't survive another episode of "Lost". But that's a discussion for another time... -- John English
Thanks, guys. 

So it looks like they're unrepairable. I'll order one of the replacements. 
-- 
John English

"John E."  wrote in message 
news:0001HW.C619CDF80095D9B4B02149AF@news.sf.sbcglobal.net...
> Thanks, guys. > > So it looks like they're unrepairable. I'll order one of the replacements. > -- > John English >
nothing's unrepairable.
> nothing's unrepairable.
Agreed. But "practicably", cost-effectively, this one is not worth it. If this was a 60" Panasonic that only needed one inductor wound, and a new PDB was not available, I'd probably think differently. -- John English
On Sat, 25 Apr 2009 23:26:22 -0700, John E. 
wrote:

>What fails most commonly in inverter circuits in, for example, 18 inch LCD >displays? > ><http://www.lcdrepair.us/1800inverterKUBNKM045A.html> > >I know anything *can* fail. But is there a common, high-frequency failure >component in these inverters?
The transformer seems to be the most common problem. I've only tried to repair about 4 of these. Three were visibly (under a microsocope) burned and probably shorted when the insulation melted between turns. One was open. All were repaired by replacing the transformer (usually cannibalized from a similar LCD inverter). I've also seen a few with fried switching transistors. However, those were probalby the result of a shorted transformer. Only once have I seen a dead CCFL tube (that wasn't broken by whomever tried to repair it previously). At this time, I don't consider it worth the time and effort to repair the inverters. I might if I can't obtain a pull-out repacement on eBay or if the LCD inverter circuitry was built onto the main driver board, as is common on many LCD computah monitors. Incidentally, I've been tempted to slop some thermally conductive epoxy on the xformer in order to improve the heat dissipation. However, without an IR camera, and more spare time, I haven't bothered. -- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
On Wed, 03 Jun 2009 05:34:10 -0400, Spehro Pefhany wrote:
> On Tue, 2 Jun 2009 12:01:51 -0600, the renowned "Bob Myers" >>Rich Grise wrote: >> >>> Speaking of that, what ever happened to the self-tuning piano? Was >>> that guy ever going to post a .WAV file or something, of the piano >>> tuning itself? >> >>I believe it turned out that the only existing documentation >>of the self-tuning piano in action was in the form of miniature >>photographs stored as multiple images on a common sheet >>of film, and these proved impossible to correctly adjust for >>conversion into any electronic media. For as we all know, >>while you CAN tune a piano, you can't tune a fiche. > > Not *alone*, certainly, but perhaps if you had a tuner helper...
Don't hire Oppornockity! For, as we all know, Oppornickity tunes but once. ;-) Cheers! Rich
On Tue, 2 Jun 2009 12:01:51 -0600, the renowned "Bob Myers"
 wrote:

>Rich Grise wrote: > >> Speaking of that, what ever happened to the self-tuning piano? Was >> that guy ever going to post a .WAV file or something, of the piano >> tuning itself? > >I believe it turned out that the only existing documentation >of the self-tuning piano in action was in the form of miniature >photographs stored as multiple images on a common sheet >of film, and these proved impossible to correctly adjust for >conversion into any electronic media. For as we all know, >while you CAN tune a piano, you can't tune a fiche. > >Bob M. >
Not *alone*, certainly, but perhaps if you had a tuner helper... Best regards, Spehro Pefhany -- "it's the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
On Tue, 2 Jun 2009 12:01:51 -0600, "Bob Myers"
 wrote:
>I believe it turned out that the only existing documentation >of the self-tuning piano in action was in the form of miniature >photographs stored as multiple images on a common sheet >of film, and these proved impossible to correctly adjust for >conversion into any electronic media. For as we all know, >while you CAN tune a piano, you can't tune a fiche.
Ngung, ngung, ngung!! -- Dave Platt AE6EO Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads!
On Tue, 2 Jun 2009 12:01:51 -0600, "Bob Myers"
 wrote:

>Rich Grise wrote: > >> Speaking of that, what ever happened to the self-tuning piano? Was >> that guy ever going to post a .WAV file or something, of the piano >> tuning itself? > >I believe it turned out that the only existing documentation >of the self-tuning piano in action was in the form of miniature >photographs stored as multiple images on a common sheet >of film, and these proved impossible to correctly adjust for >conversion into any electronic media. For as we all know, >while you CAN tune a piano, you can't tune a fiche.
Well played, sir! -- Rich Webb Norfolk, VA
Rich Grise wrote:

> Speaking of that, what ever happened to the self-tuning piano? Was > that guy ever going to post a .WAV file or something, of the piano > tuning itself?
I believe it turned out that the only existing documentation of the self-tuning piano in action was in the form of miniature photographs stored as multiple images on a common sheet of film, and these proved impossible to correctly adjust for conversion into any electronic media. For as we all know, while you CAN tune a piano, you can't tune a fiche. Bob M.
On Mon, 01 Jun 2009 21:37:25 -0700, John E. wrote:

>> Thanks for passing on your results, John. It's always nice to know how >> these things turn out. > > I concur. It's all-too-common to follow such a thread that is years old only > to find no-one cared to post the results. I like to think about the guy or > gal who is Googling a few years from now and comes across this thread. (Hi!) > ;-)
Speaking of that, what ever happened to the self-tuning piano? Was that guy ever going to post a .WAV file or something, of the piano tuning itself? Thanks, Rich
> Thanks for passing on your results, John. It's always nice to know how > these things turn out.
I concur. It's all-too-common to follow such a thread that is years old only to find no-one cared to post the results. I like to think about the guy or gal who is Googling a few years from now and comes across this thread. (Hi!) ;-) -- John English
John E. wrote:
>>> One common failure in some designs is a chain reaction failure. Poor >>> quality caps are used in the power supply and the inverter. As the >>> ESR rises the drive transistors in the inverter tend to overheat, >>> eventually shorting and blowing the input fuse on the inverter. >>> Replaceing the low quality caps, the transistors, and the fuse results >>> in a working monitor. >>> >>> The Westinghouse Westinghouse L1975NW (and equivalent Acer model) - >>> identical monitor except for the plastic - have this problem. >>> >>> PlainBill > > >> In case anyone watching was wondering, this is what I was looking for. >> Knowing what *might* be the modus operandi of this monitor is a huge leg up >> on the attack for a non-pro such as myself. >> >> Thanks, PB! And to all the others who pitched in. > > > Just to follow up... > > Replaced all the caps (using Panasonic FM series) in this monitor and it > works like new. And should last quite a bit longer.
Thanks for passing on your results, John. It's always nice to know how these things turn out. -- W . | ,. w , "Some people are alive only because \|/ \|/ it is illegal to kill them." Perna condita delenda est ---^----^---------------------------------------------------------------
>> One common failure in some designs is a chain reaction failure. Poor >> quality caps are used in the power supply and the inverter. As the >> ESR rises the drive transistors in the inverter tend to overheat, >> eventually shorting and blowing the input fuse on the inverter. >> Replaceing the low quality caps, the transistors, and the fuse results >> in a working monitor. >> >> The Westinghouse Westinghouse L1975NW (and equivalent Acer model) - >> identical monitor except for the plastic - have this problem. >> >> PlainBill
> In case anyone watching was wondering, this is what I was looking for. > Knowing what *might* be the modus operandi of this monitor is a huge leg up > on the attack for a non-pro such as myself. > > Thanks, PB! And to all the others who pitched in.
Just to follow up... Replaced all the caps (using Panasonic FM series) in this monitor and it works like new. And should last quite a bit longer. -- John English
> High ESR !
Doh!! Yes, of course. (Homer answer: "Oh, so maybe I shouldn't have replaced all those good caps?" ;-) -- John English