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Dell Inspiron Laptop only recognizes LCD just before hibernating


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#1 mitchelwb

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Posted 22 January 2014 - 01:14 AM

Sorry this is so long, but it's detailed.

 

I have been attempting to fix a Dell Inspiron 1525 that my grandmother spilled a glass of wine on.  When I got the machine, it did nothing.  It would charge the battery, but that was all.  If you pressed the power button, you'd hear it spin up for half a second then stop.  I found a parts machine craigslist and picked it up.  The parts machine actually worked well, but had a few issues.  A missing ESC key, no battery/charger and the fan was janky.  The fan worked, but would only work for a little while before it would start whining and stop.  The guy I bought it from repaired laptops and was just clearing out some excess stuff.  He was worried about selling it to someone who was going to try and use it full time and was happy to sell it to me knowing I was going to rip it apart and use it for parts.  I verified that it worked before buying it, it booted fast and had a clean install of Win7.

 

First, I swapped hard drives (Grandma's was also Win7) and booted the parts machine to verify the HDD worked and it did.  So I stripped both machines down and started to rebuild using the best parts from both machines.  After getting it all built back up, I powered up the machine and it booted just fine.  The one thing I noticed was that the screen didn't come on immediately, but did as the startup sound played.  I had no problems, played around with it to make sure all the buttons and functions were working and everything checked out.  I turned it off to finish snapping some of the last parts off like the hinge panel with the plastic power button actuator and button up the last little bits and pieces.  Then I turned it back on and this time, the screen wouldn't come up.  Windows booted and played the startup sound, but I got not display.

 

This morning, I unplugged the LCD and plugged in the other LCD.  Same thing.  Blank screen.  Machine is still booting fine, but no screen.  

 

So I hooked up an external monitor and it popped up no problem.  Device manager shows no issues.  Pressing FN-F8 to switch from external to LCD just flashes the external.  It doesn't turn on the LCD.  

 

Then something weird happened.  The machine went in to hibernation.  I noticed it because just before it did, the LCD came on.  When I woke it up from hibernation, only the external worked again.  So I sat and watched it diligently waiting for it to hibernate again.  When it did, the LCD came on just before going in to hibernation and I moved the mouse quickly to try and prevent it from hibernating.  When I did this, I now had both screens and could even press FN-F8 to switch back and forth between them.  I switched to the LCD and rebooted the machine to see if it would remember the setting.  But when it came up, it was blank again.  

 

At this point, I decided to try the other hard drive that came with the parts machine and a fresh Win7 install.  It behaves exactly the same.  Doesn't recognize the LCD.  Device manager reports no issues.

 

Booting to Bios doesn't reveal any issues that I can find.  

 

But then I booted to the Built In Self Test.  As soon as I pressed power while holding 'D', the screen lit up and started rotating through red, green, blue, black, and white screens.  But as soon as I let go, it booted to windows and only to the external monitor.  

 

I'm so frustrated trying to figure this out.

 

What I've not tried is using the HDMI port.  I assume that the RGB connection uses the X3100 GPU?  If so, I know it's working fine because it has no issue with the external monitor.  I know the LCD is connected because the BIST works.  Both Win7 instances behave the same, so I have a hard time thinking it's an OS issue.  

 

The only thing I can think of is that the Display connector has an input pin that feeds information back to the motherboard that isn't working and that's why Windows isn't recognizing the LCD.  But why does it turn it on just before hibernating?



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#2 zingo156

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Posted 22 January 2014 - 12:26 PM

If you hit f1 or f2 on boot does it go to the bios screen with the built in lcd panel?


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#3 zingo156

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Posted 22 January 2014 - 12:31 PM

There are a couple of possibilities I can think of off hand.

 

1 it is the inverter or the backlight, in your model the backlight on the lcd panel is powered by the inverter it could be the inverter is bad or the backlight has a problem. Is there any signal to the built in monitor (you will need a bright light to see if there is). With the computer on, hold the light up to the built in panel, a bright flashlight held facing the lcd panel touching it may reveal that there is a picture but no backlight.

 

2 If there is no picture what so ever on the panel and there is a backlight you may have a bad ribbon cable or an issue with the lcd/motherboard hardware. You can see if the backlight is working on the internal monitor by using it in a dark room, when you turn it on you should see some glow coming from the screen.


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#4 mitchelwb

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Posted 22 January 2014 - 12:34 PM

No.  

 

I just did a fresh boot without the external monitor.  No Dell logo, no bios, nothing.  then I plugged in the external and it popped up, displaying the bios.  

 

So even on boot, it's not recognizing the LCD.



#5 zingo156

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Posted 22 January 2014 - 12:34 PM

One more thing... there may be different controllers for analoge and digital outputs. You mentioned you have not tried hdmi, I would try every output and see if they work.


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#6 zingo156

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Posted 22 January 2014 - 12:37 PM

I am copying this from another thread but the manipulation of the lcd panel is relevant here:

 

Here are the things I would try: Try manipulating the screen by moving it around open close, push one way on one corner and the other way on the other corner (top corners when opened) to twist the screen. Do this lightly if the issue is with the panel generally moving it around will change what is happening on the screen. If you have the laptop apart and can see the video cable, you can wiggle the cable and see if it changes the output (wiggle it lightly). Make sure that you do not pull or tug on the cable at the connector ends because you do not want to disconnect them while it is on and running.

 

If moving the screen around or moving the cable around does not change anything you might start to suspect the video chip. Even if you do not see any changes it is still possible the lcd panel itself has a problem that is in the controller so manipulating it may do nothing. I will say if you move the cable around and see no change it is not likely the cable. The week point is usually where the cable runs by the hinge in the corner of the laptop. Anytime I have had a bad cable manipulating it would change the effect on the screen.


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#7 zingo156

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Posted 22 January 2014 - 12:46 PM

You may have to look back because I am getting ahead here, there is one more thing I can think of... There is either a physical or magnetic switch that detects when the lcd panel is in the down position, when it is down the lcd turns off. Sometimes they can get stuck both physical and magnetic swtiches. If it is magnetic, you could take a powerful magnet and swipe around the edges of the computer (the same side the keyboard is in but closer to the edges). if it is a physical button then there may be some small button or pin near the hinges of the laptop (again same side as the keyboard but toward the lcd panel).


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#8 mitchelwb

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Posted 22 January 2014 - 12:52 PM

There are a couple of possibilities I can think of off hand.

 

1 it is the inverter or the backlight, in your model the backlight on the lcd panel is powered by the inverter it could be the inverter is bad or the backlight has a problem. Is there any signal to the built in monitor (you will need a bright light to see if there is). With the computer on, hold the light up to the built in panel, a bright flashlight held facing the lcd panel touching it may reveal that there is a picture but no backlight.

 

2 If there is no picture what so ever on the panel and there is a backlight you may have a bad ribbon cable or an issue with the lcd/motherboard hardware. You can see if the backlight is working on the internal monitor by using it in a dark room, when you turn it on you should see some glow coming from the screen.

 

1.  I've tried holding a flashlight up to the screen to see if it's on, but I don't see anything. I don't think it's an issue with the backlight for a number of reasons.

  • The built in self test turns on the LCD just fine. 
  • two separate instances of windows can't seem to recognize the LCD
  • two separate LCD's that were both working 24 hours prior are now behaving the same.  

2. I don't think there is a picture, because I don't think the mobo is sending any signal at all the the LCD.  Again, because I have two identical LCD's that both worked just prior, I have a hard time believing that they simultaneously developed ribbon cable and/or backlight issues.   As for the internal connector on the mobo, that's the one thing I can't double check.  But again, the self test works fine and the LCD comes on just before hibernating, so I know that at least the power and output signal from the motherboard are working.

 

The only thing that makes even any remote sense is that there must be separate/dedicated output and input pins on the connector (I've not looked up a pinout for it) and that the input pins from the LCD to the mobo are not working/connecting.  This would mean that the system isn't getting any kind of notification from the LCD that it's there.  

 

But then why does it work in self test and hibernation?  My only guess would be that the self test doesn't care if something is there, it's going to blast an output signal no matter what. And for the hibernation, I can only guess that Windows does the same, sends out an information blast to any and all potential monitors that "hey, listen up, I'm going to sleep in a moment"

 

I have inspected both the mobo connector and the ribbon cable connector with a jewelers loupe and can't find anything that looks dirty or buggered up.  I've not tried any kind of contact cleaner, mainly because I don't have any.  



#9 zingo156

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Posted 22 January 2014 - 12:52 PM

http://www.technibble.com/forums/showthread.php?t=17075 that thread the person says the magnetic switch is near the palm rest or touchpad... This would be my first test. Take a very strong magnet and swipe it over that area a few times. Or you could open and close the lid a few times in a row quickly and see if it wakes the lcd panel. You may have to take it apart and check the conncetion as the person in the link did.


Edited by zingo156, 22 January 2014 - 12:54 PM.

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#10 mitchelwb

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Posted 22 January 2014 - 12:55 PM

You may have to look back because I am getting ahead here, there is one more thing I can think of... There is either a physical or magnetic switch that detects when the lcd panel is in the down position, when it is down the lcd turns off. Sometimes they can get stuck both physical and magnetic swtiches. If it is magnetic, you could take a powerful magnet and swipe around the edges of the computer (the same side the keyboard is in but closer to the edges). if it is a physical button then there may be some small button or pin near the hinges of the laptop (again same side as the keyboard but toward the lcd panel).

I did consider a switch that would recognize that the laptop was closed... but it's not a physical switch... I forgot to follow up on that!  Thanks for reminding me.  That would also explain one other issue I had with it yesterday, it kept trying to go to sleep while running updates... It only did it a few times, and only in a short time period, but if it thinks the lid is closed, that would explain that too!  



#11 zingo156

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Posted 22 January 2014 - 12:57 PM

See the post just above your most recent one... The switch should be near the palm rest/touch pad. Open and close the lid a few times quickly or use a strong magnet and swipe the area a few times...


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#12 mitchelwb

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Posted 22 January 2014 - 01:28 PM

That's it!  The little status light board has the magnet on it.  I unplugged it and the LCD came right on! 

 

When I plug it in however, it immediately turns the LCD off.  My first thought was to swap the indicator board with the one in the other machine, but then I remembered that when I took the donor machine I got off craigslist apart, that board was disconnected.  I assumed it was only indicator lights and probably the last time it was opened (I knew it had been worked on before) they just forgot to plug it in.  But now I know why it wasn't plugged in.  When I rebuilt it, I used the board from my grandma's machine because it's attached to the wrist rest and her wrist rest was nicer.  This means that it doesn't matter which indicator board is plugged in, it's going to behave like this.  The problem appears to be in the mobo or the mobo connector.

 

So either I leave it unplugged and have no indicator lights, or I plug it in and it becomes a desktop.  Or I go with plan C and try cutting out the pin for the magnet and see if I can make the lights work and just live without it going to sleep when you close the lid.

 

 Thank you so much for helping me work through this!



#13 zingo156

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Posted 22 January 2014 - 01:38 PM

I am glad I could help. Good luck, be careful cutting the pin.


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