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Video Card, LCD Cable, MoBo? No clue. Screen issues.


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13 replies to this topic

#1 compguy66

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Posted 22 December 2017 - 08:46 AM

Hi everyone, I've known about this forum for a long time but never really needed help until this moment. I figure maybe someone can give me their best guess before I dig further...

 

I have a Toshiba L75D here with a screen that is acting up. I was told that there may have been pressure put on the display. 

 

So i took apart the display assembly, and jiggled the LCD cable to see if it made any changes to the screen. Nothing. So I was guessing it wasn't loose and is just the screen. 

 

Replaced screen. I booted once and it was fine. Turned off to reinstall all screws etc. Turned back on, same issue as before. Odd.

 

So now I'm thinking maybe it is the LCD cable. 

 

It's hooked up to an external display, so for sh-ts and giggles, I try to 'extend' the displays, rather than duplicating them.

 

The laptop LCD now works fine.

 

I maximize a window. The laptop LCD goes white with lines again. 

 

I choose second display only, then back to duplicate and the laptop screen works again. I can repeat this to infinity.

 

I have a video of it here -- https://photos.google.com/share/AF1QipPfUzHcR1CsuwpiKZbCAhWCQICWbYueOZhhXnNuHfSCMN-O3hlHwSW5Vo4NVTbVsA?key=TGJaMUpWc0hyYk5jd0UzWjlXN0s2bDBIWkhKYmlR

 

I'm wondering if anyone can give me an educated guess as to whether or not it may be a driver issue, or if it is a video card issue (I'm hoping not). 

 

It has a discreet video card - AMD 8330 I believe. I have rolled back drivers, didn't work. I have uninstalled all AMD software entirely and it is now running on a generic video driver. No luck.

 

Anything?

 

Thanks!



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#2 mightywiz

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Posted 22 December 2017 - 12:22 PM

try pushing on the ribbon cables that go from the pcboard on the display that feeds to the actual lcd screen.  sometimes they can be bad and that's what will cause the lines on screen.  especially the edges of the ribbon cable where they are attached to the glass screen.

 

so if your lines are different between the old screen and the new screen then you probably bought a bad replacement screen from someone.   I never buy used replacement lcd screens for this reason. 

 

youtube "repair lines on lcd screen" and you'll see what i'm talking about.


Edited by mightywiz, 22 December 2017 - 12:23 PM.


#3 compguy66

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Posted 22 December 2017 - 12:46 PM

Hi MightyWiz, the replacement I bought is, supposedly, new. I agree with you and I wouldn't buy a used part like this.

 

Would it be possible to be the ribbon even though the display functions normally once extended or duplicate screens are selected? I almost feel as though something like that would confirm it is not the ribbon or display. Rather software or the video card itself.

 

Thanks for your input.



#4 mightywiz

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Posted 22 December 2017 - 01:31 PM

try switching resolutions just in single monitor mode (no external connected) maybe it is your GPU and it's having issues in specific resolution modes.   im curious to see if it is a resolution issues your having.  I know when you connect an external monitor it can change your laptop display setting to a compatible setting that works with the external monitor.



#5 compguy66

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Posted 22 December 2017 - 01:34 PM

Hi MightyWiz,

 

I've tried changing resolutions / frequencies (albeit their's only one for the LCD). Compounding the issue though, is that I cannot see anything on the laptop's display, it is bright white with lines as distortion. I can only navigate settings, etc. through the secondary display. I did this with the monitors duplicated, so I'd imagine the settings would be applied to the laptop lcd as well. 

 

For what it's worth though, yes, i've tried changing up resolutions, etc, rotating the display and whatnot. made no difference

 

Thanks.



#6 mightywiz

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Posted 22 December 2017 - 02:00 PM

so are the pattern of lines the same between the old screen and the replacement screen?  if they are the same then I'd suspect the computer hardware either gpu or cables.  if the line patterns are different then I would suspect

both screens are bad.

 

this is a weird issue!

 

"Replaced screen. I booted once and it was fine. Turned off to reinstall all screws etc. Turned back on, same issue as before. Odd."

 

so If you take the screws out does the problem go away?  you might visually inspect to make sure your not pinching a ribbon cable or wires when you put screws in.  or even flexing the board because a wire is not routed correctly.


Edited by mightywiz, 22 December 2017 - 02:02 PM.


#7 compguy66

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Posted 22 December 2017 - 02:08 PM

the patterns of lines are not the same, but very similar (vertical lines moving and very bright screen).

 

regarding the screws etc, i booted it up, screen worked. left for a minute, came back to start it up so I could take a photo for the owner before I screwed it back in (I basically had just seated the display and the cable). I'm sorry if that was confusing, no, I never got around to completely reinstalling it before it reoccurred.

 

my confusion with it being a bad screen is, why does it work fine when I change it to extended? for what it's worth, one thing i didn't mention is that, in the process of switching from duplicate to extended etc... if the screen is working after I do the duplication trick, and I deactivate the external display, the main display on the machine works.

 

i've done a lot of work on computers and it's all very, very odd. 

 

thanks for your help



#8 mightywiz

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Posted 22 December 2017 - 02:12 PM

me too!  I've replace a lot of screen over the years.   my gut is you got a bad replacement screen!



#9 mjd420nova

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Posted 22 December 2017 - 10:00 PM

Besides what looks to be a bad cable between the display and the main board, I have seen this as a driver issue.  The program gets a different driver loaded for that screen at that resolution and when switching back to the previous screen, it defaults and can't display that mode.  It is  strange and I've not found the driver or mode that causes the display to blank or lose sync.



#10 compguy66

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Posted 23 December 2017 - 06:21 AM

hi mjd, 

 

do you think a cable would be responsible even though the display works after switching between expended, duplicate, then single screen? I would imagine a bad cable would just not work at all, regardless of the setting.

 

thanks mjd

 

Also, one key clue that I left out inadvertently -- the screen is messed up from the time of boot, so I dont know if it would be a driver issue. can someone confirm this?

 

thanks



#11 Platypus

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Posted 23 December 2017 - 06:52 AM

the screen is messed up from the time of boot, so I dont know if it would be a driver issue. can someone confirm this?


It cannot be a driver issue before Windows loads, the video is running purely as hardware until Windows loads a driver. This and the fact that the screen is normal when duplicated under Windows (meaning the LCD panel and LVDS cable running up to it are actually working normally) suggests the fault is in hardware, either the video chip or the video RAM where the screen buffers are located.

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#12 compguy66

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Posted 23 December 2017 - 09:01 AM

thanks for confirming, platypus. 

 

unfortunately i don't do any work on chips, i'd imagine the video ram is soldered to the chip, so that's not an option either.

 

guess he will have to run it on external or pay $$$ for someone to do the work. 



#13 compguy66

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Posted 23 December 2017 - 09:06 AM

sorry just to piggy back on that last post...

 

I don't believe this is the case (I'm just trying to rule out everything), but if i used teamviewer to remote desktop into the faulty machine, would a graphics card problem be mimicked in it? I would imagine it wouldn't but im just curious.

 

thanks.



#14 Platypus

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Posted 24 December 2017 - 12:31 AM

If my expectation of how teamviewer should be handling the video is correct, it might go either way, like when you switch the display modes. What teamviewer should be doing is showing you the contents of the screen buffer in the laptop. If you see the laptop's desktop correctly when it's bad on its own screen, that would mean the screen buffer memory contents are intact, and the circuitry sending the signal out to the laptop screen has the problem. If teamviewer shows you the same bad image, it's probably the video RAM faulty.

 

What is the complete model number of the laptop? Since the video on that model seems likely to be on a replaceable module, we might be able to find out a cost for a replacement.


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