LCD Inverter - Screen Diming issue

[xxsilk109xx]

Compaq CQ60 - Customer said the screen went dim, took it to another shop, tech replaced the inverter, laptop has been working for the past 6 months or so. Today she brings it to me.

Computer boots up fine, no screen issues, inverter is working. So I ran FurMark to try to get the inverter to shut off, FurMark ran and the screen never dimmed. So I let it sit and noticed that the computer shut the display down, so I moved the mouse and the picture came up fine. So I left it again and came back and it flickered and the image came back but with no backlight!!!!!

I then closed the lid and reopened the computer and the display came back on.

I am unsure if this is an inverter issue, my experience has been that when they are bad they are bad, not work half the time and not the other half.

Could this possibly be changed by a power setting? If so how would this affect only the inverter.

edit - even while on the login screen, when left for sometime the inverter seems to "turn off" and cant "turn on" without restarting the computer or closing the lid and reopening

 

[Encrypted Existence]

Test it with a boot disc to see if the problem persists. This will tell you whether the problem is hardware or software related.

 

[xxsilk109xx]

tested with Hirens disk and its went dim as well.

I guess its an inverter, could it be anything else though? Concerned since this one was replaced 6 months ago (although I dont know if it was an actual new one or not).

Can inverters just act funny like that? I thought they either worked or didnt.

 

[DCGPX]

Possibly, it could be on its way out, you closing lid just makes it restart ccl.

Think of it as a choke in a fluorescent light, they die and resurrect when switched off then on. Still dying.

I'd replace seeing how cheap they are.

 

[Encrypted Existence]

tested with Hirens disk and its went dim as well.

I guess its an inverter, could it be anything else though? Concerned since this one was replaced 6 months ago (although I dont know if it was an actual new one or not).

Can inverters just act funny like that? I thought they either worked or didnt.

I am not sure if inverters have been known to act funny like that. Could also be the mobo, video cable, or LCD. Have you run any diags yet?

 

[xxsilk109xx]

I am going to replace the inverter...

I guess my main concern is that the replacement does not burn out due to something in the motherboard, etc. causing them to go bad.

 

[Encrypted Existence]

I am going to replace the inverter...

I guess my main concern is that the replacement does not burn out due to something in the motherboard, etc. causing them to go bad.

This is why it would be beneficial to run a full diagnostics first so you don't waste your time playing the guessing game.

 

[xxsilk109xx]

Well I have checked the lcd cable, it seems to be perfectly intact and shows no signs of wear anywhere and the cable is firmly connected at all three points.

My multimeter does not have the capability of testing the inverter output.

I am going to tear down a junk laptop tomorrow and see if its the LCD itself, that is the only thing I can test for sure as I dont have another lcd cable or inverter in stock to test.

How could I test the mobo for this?

 

[Encrypted Existence]

Well I have checked the lcd cable, it seems to be perfectly intact and shows no signs of wear anywhere and the cable is firmly connected at all three points.

My multimeter does not have the capability of testing the inverter output.

I am going to tear down a junk laptop tomorrow and see if its the LCD itself, that is the only thing I can test for sure as I dont have another lcd cable or inverter in stock to test.

How could I test the mobo for this?

I wasn't talking about a specific test but rather mobo (and other) diags in general. Even if the problem doesn't seem to be caused by a certain piece of hardware it is good to run full diagnostics anyways just to be certain. In the process you may find other hardware that has failed/is beginning to fail and this will enable you to better service your customers if you can tell them that there are other unrelated problems (even if they choose not to have you fix them it is the professional thing to do IMO).

 

[Mr.Mike]

Does the behavior persist when connected to an external screen?

 

[kevinjhaag]

If the inverter doesn't cure the problem, then a LCD screen probably will. Without test parts it sucks because you can't just try another inverter or LCD screen. Well I had the test parts so it made it easy for me to test this same issue. But as others have said, run a full diagnostics to make sure their is no other problems. Good luck and take care my friend.

 

[AlaDes]

Compaq CQ60 - Customer said the screen went dim, took it to another shop, tech replaced the inverter, laptop has been working for the past 6 months or so. Today she brings it to me.

Computer boots up fine, no screen issues, inverter is working. So I ran FurMark to try to get the inverter to shut off, FurMark ran and the screen never dimmed. So I let it sit and noticed that the computer shut the display down, so I moved the mouse and the picture came up fine. So I left it again and came back and it flickered and the image came back but with no backlight!!!!!

I then closed the lid and reopened the computer and the display came back on.

I am unsure if this is an inverter issue, my experience has been that when they are bad they are bad, not work half the time and not the other half.

Could this possibly be changed by a power setting? If so how would this affect only the inverter.

edit - even while on the login screen, when left for sometime the inverter seems to "turn off" and cant "turn on" without restarting the computer or closing the lid and reopening

It sounds to me like it's a loose cable connection or a backlight going bad. I've had several Compaqs that I've replaced screens in with a similar issue. Replacing the screen fixed the problem on all of them. However, I do remember one of them having a backlight going bad as well as a cable that needed reseated on the motherboard. Although I had tried reseating the cable (screen and motherboard) numerous times before replacing the screen, I still had to reseat the motherboard end of the cable one more time after installing the new screen. That one was a real pain and just to ensure the original screen really was flaky, I tested it in another laptop and it flickered in it as well.