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Inverter

Posted on 2006-06-14
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Last Modified: 2008-03-04
Having problems with the display on my Inspirion 7500. I replacd the cable that goes to the display but I get nothig. It will furnish video to an external monitor. One of the tech's said I probably would have to replace the inverter. I want to know If the inverter is the small circuit board located behind the display and if not where is it located.
Any assistance will be greatly appreciated.
Thank yu
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Question by:Irv9
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by:bryanford
ID: 16909041
Ive had inverter problems in the past and have successfully replaced them.

The following is what an inverter looks like for a dell latitude. Should be similar if not identical for the inspiron:

http://www.laptops-we-r.com/images/Latitude%20L%20Series/DELL%20LATITUDE%20LS%20LCD%20INVERTER%206134T.gif

Just a question, can you see a very very VERY faint image on the LCD? when mine went, you could see the windows xp start screen if you looked at it close enough. If so, it would be your inverter, but thats not to say its not if you cant see it.

Bryan
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by:nobus
ID: 16909461
could be backlight, or inverter; look here :
http://www.lcdpart.com/doc/ccfl.html      
http://www.lcdpart.com/doc/inverter.html
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by:Irv9
ID: 16910415
The display is bland but the video works on an external monitor. I will check these out and get back  to you
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by:bryanford
ID: 16910421
The video would work on an external monitor because an external monitor doesnt rely on the inverter.
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by:nobus
ID: 16910570
..or has a working backlight
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Author Comment

by:Irv9
ID: 16911213
Thhis problem is the result of a hinge breaking and pinching the cable. With the cable pinched I would not get a picture but wavy lines like the problem of a vertical or horizontal hold going out on a tv. I replaced the cable with the correct part # etc. Now I get nothing on the display. It has such nice sharp video that I hat to send it to the landfill, but due to its age I am reluctant to spend much money on it.
Thought this input might shed a little more light on the subjec.
Thanks to all who have answered.
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by:GinEric
ID: 16925939
Most of those backlights use Inverters to boost the voltages up to around 200 or 300 VDC, like the high voltage circuit on any TV.  The outermost cables on a ribbon cable are also usually the voltage lines.  If you pinched the 200 or 300 Volt cable and it went out onto the case, it's likely you blew out the display's chips or fragile circuitry somewhere.

Inverters generally convert AC to DC, or DC to AC.  Even if DC to DC there's an AC in the middle, a step up type of inverter.  They call this conversion "inversion" simply because it inverts the type of voltage from one form to the other, AC or DC.  [Alternating Current or Direct Current]

Buying a new one is definitely the less expensive way to go.
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Author Comment

by:Irv9
ID: 16926327
Thanks Gin.
How do yu account for the fact that I had a for want of a better word, " distorted video after I pinched the cable, and no video or even a light on the screen after I replaced the cable. Thanks so much for the explanation.
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GinEric earned 125 total points
ID: 16929628
Burning things out, like a high voltage circuit, take time.  And repitition of the problem conditions.  You were probably feeding the video chip, after super pulsing it, with a signal suffient to continue the decay of the fragile substrates, the doped p and n juntions, whose characteristics, resistance, current, were changed by the pulse.  It's called component burn in under normal circumstances; the resistance goes down,t he current goes up, which causes the resistance to go down further, which causes the current to increase further, which, at some latent point burns the circuit open or shorted.

And just because you had no video on the screen, doesn't mean you didn't still have voltage and current on that cable, which was continually pulsing and burning things out, say, if you tried to turn it on even just "a few times."

Sidewise lines or bars is a clear indication that the horizontal hold has gone, even in LCD, in some high voltage related circuit.

With the old TV's, you actually heard a "Fizzzzzzzz!" right before it burnt out.  It takes time, that's all, it doesn't happen instantaneously, nothing does.

I could rely on and prove it with the math, the Calculus, but I don't think we need to go that far, do we?

I've seen a guy burn out a megawatt inverter; that was not pretty, and, it was because he had his cables, the three phase delta wiring wrong; he left one left ungrounded [unearthed so that there was no reference voltage and two phases rolled over to an induced higher voltages and currents in the third leg].  I've also seen some very stupid people "touch" the wrong "inverter," get stuck to it, like "paddles" in an operating room; not pretty either, and usually we had to "bring them back to life."  You're lucky, the computer inverter shouldn't be able to electrocute you, but it can electrocute itself, often causing electronic coma first, and then after a time, a slow death.

Thing of the video squiggly lines like an alarm on a heart monitor, they say "I'm dying!  Please help!"
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Author Comment

by:Irv9
ID: 16929718
Thanks so much for the explanation of what probably happened. In my many years of asking for help from Expers exchange your answer and discription of the problem is by far the best I have eer received. You will never know how much I appreciate you taking the time to to go into such detail.
Thanks again.
Irv
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by:GinEric
ID: 16930421
Thankis Irv9.  It's always a pleasure to provide information to someone who actually wants to know details.
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