Absolutely no screen

Hello,
I hope someone will be able to help me.

I have replaced a screen on my laptop (Toshiba Satellite U500). I have done this on other computers without problems. This time I am afraid I might have damaged the wires as I cannot get the screen to work. The external monitor goes blank when connected (a change from "Check Signal Cable" message it gives me when not connected) so, obviously, something is working.

Could anyone suggest a guide or a procedure to follow to locate the problem?

 

Have you checked
Cable at rear of screen is fully inserted
Same on motherboard
Tried pressing FN + F5 to see if it switches to screen , or, external (sometimes need to hold down keys as system starts.
Have you checked the invertor cables ( INPUT POWER, AND OUTPUT TO SCREEN BACKLIGHT)
Is there a small earth cable to the base/coming out of the screen cable, and if so, is it connected.
Can you see a very faint image, if you shine a torch to the screen
Have you tried the f6/f7 buttons to increase the screen brightness

 

I have checked all cables, tried the F5 combination, it is not working.

What cables are those? I think all of the cables are connected...

Is this the one that looks like a loop? I have one like that... (can't figure out where this must go)

I tried, I do not think it is related to that....

As soon as I plug the external one in the "No Signal" screen changes to a black one...

 

Do you have a bootable CD around you could see if you get anything else on the external monitor?

Seems to me it may be something other than just the monitor that is holding up POST. (Shouldn't you have a Toshiba splash screen?)

 

This a guide for a similar model. http://www.irisvista.com/tech/laptops/Toshiba-Satellite-U405D/remove-screen-inverter.htm

They are only showing three connections.

 

How would that work? :confused The computer is loading, but I do not see any result on the screen.

I have no splash screen, no image at all.

Thank you. It may be the inventer board, but how would I be sure?

I also have a direct question: What does it mean (in terms of what works) if the external monitor (as soon as I plug it in) turns from "No Signal" to black?

This is my last reasonably powerful computer I really hope I could fix it...

 

I'll defer to Baklogic on specifics.

So you are saying you are hearing Windows load (activity for about a minute) but nothing on screen?

On the inverter you should be seeing a very faint image if you shine a strong flashlight on the screen.

http://www.laptoprepair101.com/laptop/2009/05/04/how-test-lcd-screen-inverter-in-laptop/
http://ask.metafilter.com/92210/Backlight-or-Inverter-How-can-you-tell

But this might not be the case since the external isn't working either. I'm not sure what it means that you are getting a black screen instead of no signal. Like you said the monitor is getting something but perhaps the problem is in the graphics chip?

Was either the external or internal monitor working before you replaced the screen?

 

Yes, the lights switch on (above and below keyboard).

 

Sachs has given a very good site for Laptop repairs- If you follow its links, you will see much more.
Basically, I had one acting like yours, and as the screen actually changes, does the power light change colour ? - on ine it did , and then flashed red (as the laptop screen came on.
If there is a flashing little white bit, you have video, but could have a faulty hard drive, or, other hardware problem.
The answer could be that the fn/f5 switch works intermittedly, as mine did.
Try pressng the fn/f5 combination immediately that you start the laptop.
Then if nothing shows on the external , or, internal screen, try pessing f2, as you start up to see if it kicks int the bios screen.
I had to do the fn./f5 several times before mine would kick into the bios, so patience might be the word (not the hammer we used to think of...) I thought after the first couple of try's thatit had a bad video chip.
If it eventually kicks in and either the external, or, internal screen shows, then you are in business- if after much patience,it does not, it is most likely the video chip, and therefore motherboard fault (I have a Toshiba L450 at the moment that is acting dead graphics, that I have been working on, so I know what you are up against)
It is worth shutting down the Laptop, after each non start, and trying the f button on next start, if no picture shows on either screen - I got aToshiba L300 to give me a picture that way (Hard shutdown, by pressing and holding down the start button )
If you have aninternal wireless card, it can be worth trying the same procedure with that removed, as dodgy wireless card has been known to affect things, as has a dodgy stick of Ram.
If you do get into the Bios screen go to the display part, and choose both to show , -save and exit, and it should work okay , then
If you keep the external screen attached until you can get a picture on the aptop, then, o.k
If you don't get a picture on the laptops own screen, but do get one on the external, then track through, as I said before- cable, then invertor (often the culprit), then the screen itself, unless you already tested that.

 

Sorry Tomi, somehow, I did not get your reply to Sachs, when I started (must have been between posts, somehow) and you have done the main bit- Still its all there, if anyone else needs it.

 

Quick follow up- if bios is set to external only, laptop screen will not show, if set to lcd, laptop screen only willshow. Set to both in bio, both screens will sho- then if no laptop screen, ... follow on with invertor, cable, and screen test.