Dim screen on laptop.

[The Birddog]

Hi Everyone,

I had a Laptop in with a dim screen, so I guessed eithher the invertor or the backlight had gone - it's a compaq EVO620C.

These screens are made complete so no access to the invertor or backlight. I bought a second hand screen on ebay, from a person who said the screen was working, it was taken from a laptop with a faulty motherboard.

I changed the screen with the one from ebay and I still have the same problem. The motherboards ok, I can get a display on an external monitor.

Any ideas anyone, I am stuck with this one...Help...please...

The Birddog.

 

[cbclark]

Well, you tried adjusting brightness manually with the Fn key I assume?

Also, I was able to find inverters listed for this model, be sure it's not hiding down along the bottom edge of the screen just behind the bezel.

 

[14049752]

These screens are made complete so no access to the invertor or backlight

Just curious, but what do you mean? I've never seen a laptop lcd that you weren't able to access the inverter. Did you buy a lcd assembly? Because you can take the front bezel off, just remove the pads covering the screws, remove the screws, then pop the cover off and you should expose the inverter....
If you already knew that and the inverter is built into the lcd panel itself, could you post some pictures?

 

[The Birddog]

Hi,

Thanks for the posts.

You can see the invertor but you cannot get at it unless you remove the bezel which is glued, not screwed down. The bezel is made of really thin metal and there is no way of getting it off without damaging it. A laptop specialist told me that you have to replace the whole screen. Its unlikely that both invertors are broken aswell dont you think.

I have tried the brightness controls and it makes no difference.

 

[14049752]

If possible, I'd really like to see pictures of this. I haven't come across anything like what you're describing...

Ok, my curiosity was killing me. I found a high resolution image of an EVO 620c through google. I've worked on this series of laptop, there's nothing to it.
Here's a link to the screen. The red circles show where the screw covers are, you just peel those off to reveal the lcd panel and inverter. As far as the metal bezel...that's the lcd panel's frame, I'm assuming. You typically don't take the screen that far apart unless in a clean room, otherwise you'll get dust in the screen and possibly have air bubbles and fingerprints and things...

Here's a link to a picture of the inverter, just because.

 

[juiceman39]

I have a Dell that has a brightness adjustment in the Bios. Also a gateway that uses the function keys. Some Must be plugged into AC to get brightness.

 

[The Birddog]

Ok 14049752, I will send you a photo of this but can't until monday when i'm back in the workshop.

The screw covers you show at the top of screen simply arn't there though, on both of the screens.

Thanks for your help by the way. Do you have an idea about why the screen is dim though?

 

[14049752]

Do you have an idea about why the screen is dim though?

The screen is dim for one (or a combination) of three reasons, ruling out settings which I'm sure you have:

1. The inverter is not providing power to the CCFL. Since you already replaced the whole assembly, you might be able to rule this out...but it could be a bad part.

2. The CCFL is broken or bad. Same as above, would have likely been fixed by replacing the screen.

3. The motherboard is not providing power to the inverter. I had this happen a few times, it's fairly hard to diagnose because of each laptop's individual pin out. Sometimes you can see evidence of damage on the board, but not always.

I'm curious to see those pictures. This type of problem is much easier to diagnose if you can get to the individual parts.

 

[The Birddog]

Thanks again 14049752, please watch this post and I will post pictures ASAP, by the latest Monday.

 

[robert152]

I think 14049752 got it right. I ran into the same problem with a customer's computer. Screen was really dim, so I naturally went to the inverter and changed it out, nothing. Next I changed out the LCD, nothing. (I had all these parts laying around THANKFULLY).

It came down to the actual motherboard not supplying the inverter board with the necessary voltages.