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Old 05-03-2012, 07:34 PM
tek9 tek9 is offline
 
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Default Inspiron 700m LCD lid switch broken

I'm working on a Dell Inspiron 700m, and the LCD cutoff/lid switch is cracked off. It's the silver rectangle to the left of the screw in the picture. There used to be a plastic piece sticking up and out of it which was somehow triggered by a plastic pin on the bezel cover, and that's what broke off now.
Now that the plastic piece is broken off, it seems that it's stuck in the "off" position, and doesn't allow the backlight to turn on. I replaced the inverter, in case that was the problem, but nothing doing, so I'm assuming it's this switch.
Is there any way to "fool" the system into thinking it's in the "on" position, or just to tell it to "ignore" that switch"?
(p.s. it's not a customer's computer, just one I'm practicing on, and hoping to use onsite as an Internet browser and such.)
Any help would be appreciated....
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Old 05-03-2012, 08:26 PM
abyssinian abyssinian is offline
 
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That switch is "NO" (normally open). When the lid is shut, it closes the circuit.

To "fool the laptop" that the lid is always open, you can remove that switch entirely. However, it appears from your picture that the trip lever is broken/missing. I would think that in this condition, the switch should already be "open"...unless part of the lever is still inside the switch.

You can check the open/close condition of the switch with your DMM (although it has 4 terminals, it is being used as a SPST switch).

P.S. I always loved the Dell 700m/710m for their portability....since long before netbooks, tablets, and smart phones. I have owned somewhere between 5 and 10 of them.

Last edited by abyssinian; 05-03-2012 at 08:37 PM.
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Old 05-03-2012, 08:39 PM
tek9 tek9 is offline
 
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Quote:
Originally Posted by abyssinian View Post
That switch is "NO" (normally open). When the lid is shut, it closes the circuit.

To "fool the laptop" that the lid is always open, you can remove that switch entirely. However, it appears from your picture that the trip lever is broken/missing. I would think that in this condition, the switch should already be "open"...unless part of the lever is still inside the switch.

You can check the open/close condition of the switch with your DMM (although it has 4 terminals, it is being used as a SPST switch).
Thanks for replying, but I'm really green at all this, so please clarify:
How should I check the condition of the switch? Which contacts should I touch with the DMM to check open/close?
Also, you're saying that if I'd remove that entire rectangular thing, the system would see it as being always open?
Thanks for your time....
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Old 05-03-2012, 09:31 PM
abyssinian abyssinian is offline
 
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In your picture, the upper left and upper right terminals are connected together electrically (the laptop sees them as one), and the lower left/lower right pair are also connected together. Place one meter lead on either of the top two terminals, and the other lead on either of the bottom terminals. You want an open circuit between these, for the LCD backlight to turn on.

Yes, if you remove the entire switch (the "shiny rectangle thing"), the LCD will always stay on.
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Old 05-03-2012, 10:50 PM
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Quote:
Originally Posted by abyssinian View Post
In your picture, the upper left and upper right terminals are connected together electrically (the laptop sees them as one), and the lower left/lower right pair are also connected together. Place one meter lead on either of the top two terminals, and the other lead on either of the bottom terminals. You want an open circuit between these, for the LCD backlight to turn on.

Yes, if you remove the entire switch (the "shiny rectangle thing"), the LCD will always stay on.
Yeah, you're right. It was an open loop between those terminals.
I suppose I'll need a new screen next.
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Old 05-04-2012, 12:53 AM
abyssinian abyssinian is offline
 
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You may consider replacing the CCFL bulb in your LCD. The bulbs are cheap...less than $10 including shipping. It is very delicate work, and the results will be less than 100%. Even if you don't break anything you will have a spec or two of dust in the screen, and/or the lighting will be uneven. But you may enjoy the challenge and learn something along the way.

There are other faults besides the inverter and CCFL that can cause a "no backlight" issue, so it would be a good idea to verify for certain that another screen (or CCFL) do in fact work with your laptop first.
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Old 05-04-2012, 01:14 AM
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I began taking apart the screen already to check out the CCFL itself. I'll see if I can take apart a different screen I have lying around to see if that CCFL will work. When I have the time..........
Thanks.
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Old 05-04-2012, 02:12 AM
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Now I'm confused.
I took apart the screen and took out the CCFL, plugged just the CCFL into the inverter and powered on the machine, and the backlight's ON.
If it's not the inverter, nor the CCFL by itself; why would the screen be dim when it's put together?
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Old 05-04-2012, 02:07 PM
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*bump*
Can anybody help me figure this out?
What would cause the backlight to work out of the case, but not when it's assembled?
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Old 05-04-2012, 02:14 PM
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Short? Loose connection? Try putting it back together again and see if it works now.
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