Hi.
Over the past week, the screen on my HP Pavilion ZE4323 has started to go very dark shortly after start up. Windows XP is still running as normal - I can make it out if I shine a torch on the screen.

I've solved the problem to a certain extent by using the 3 restore discs to restore the factory settings. The result is that the screen shows the installation process and then runs through the introductory video ok. If I leave it with the desk top showing, there's no problem. No darkening of the screen at all.

However, if I go to the next step and try and install SP2, the screen darkens about 5 minutes into the installation process. A similar thing happens if I try to read something off an external hard drive.

At first I thought it could be overheating. So, I completely dissembled the laptop, took the fan and heat sink off, used an air can and generally cleaned it up. This doesn't seem to have made differnce though.

I then thought it might be the backlight or the cable connector. Don't think so, because as I said above, it's fine when use the restore disks. In fact, provide I don't do anything other than move the pointer around the desktop, all appears to be well.

Any ideas, please? Corrupt Windows or registry, or perhaps a virus?

Regards

Corrupt Windows or registry, or perhaps a virus?

No. The inverters for the backlighting failing in the monitor is most likely your problem. The clue that gives it away is that you can see the image when you shine a light on it. The inverters cost from about $50 to $120 depending on the model monitor, and take about 1 hours of labor at most computer shops that work on notebooks.

Well, I'm not so certain that could be the case - how could that cause an intermittent problem?
I would assume the backlight either works or it doesn't, unless it is being controlled by software.
Unless perhaps there is a loose cable, but that still wouldn't explain why it fails only when the computer is in use.

Does the backlight switch on and stay on as normal if you don't boot windows?
For example, if you open the BIOS settings as soon as you switch it on, or boot into a live CD like Knoppix Linux. (you can download the disk image here: http://ftp.uni-kl.de/pub/linux/knopp...7-01-04-EN.iso)

I would suggest trying that, as if it is still faulty running a live CD that rules out Windows or any software you may have installed as the cause so it must be a hardware issue.

If you are certain it is a hardware issue, as you are clearly happy to dismantle your laptop I would recommend opening up the laptop screen assembly and looking for worn/friction-damaged cables, or maybe even heat damage.
If you cannot see anything obvious, and tilting the screen whilst on does not affect it, then finding a source and buying a replacement backlight inverter as Digerati mentioned would possibly be an option. But depending on your exact model it could also be a few other things, maybe even the bulb/tube itself.
For example, it could the switch which turns your backlight on/off when you close the lid could be stuck or faulty - sometimes that is obvious, but it may be magnetic making it a little harder to find.
Here is the service manual for your model: http://h10032.www1.hp.com/ctg/Manual/c00246219.pdf
It shows you how to remove the display assembly, but not dismantle it.
Therefore, you may want to have a look at prices for a new display assembly (including LCD) before you go ahead and dismantle it. Try eBay if the prices scare you. =)

-Andrew

Well, I'm not so certain that could be the case - how could that cause an intermittent problem?

Huh? Ummm, I see you're not too familiar with electronics. That's ok. Most computer users and IT professionals are not hardware technicians. Understand that all kinds of problems in electronics (and mechanics) can be, and often are intermittent for awhile before finally failing completely - if they ever do fail completely - with software having nothing to do with it.

As I noted - the key clue here is shining a flashlight and seeing the image.

I would assume the backlight either works or it doesn't

Sorry but that's wrong too. You can't assume that with anything - especially electronics. You might want to read with the help of Google on how LCD monitors work or calibrating LCD TV. Note here where it says,

LCD displays have controls labeled BRIGHTNESS and CONTRAST...the BRIGHTNESS control, or the control with that icon, typically alters the backlight luminance

Since the output of backlighting can be altered, there is obviously more than one "state", it is not just on or off, working or not.

unless it is being controlled by software.

Sure, nearly everything digital is controlled by software, perhaps hard coded in a logic chip somewhere. But since we know LCD monitors work without being connected to a computer, you sure don't need to boot to an OS, or load up software to view anything. The brightness of the backlight is a set and forget setting. It is not being adjusted on the fly by any controlling software.

Replace LCD Monitor

Bill, I apologize if you feel I gave false information, but to be honest I found your reply slightly patronizing.
My knowledge of electronics may not be anywhere near your qualifications, but I know enough to describe in detail how almost every piece of hardware in a computer works. I spent a few years running a small business
I think you have disregarded my post based on the first two lines, which in hindsight are not very well worded.

What I was trying to get at was the link between backlight operation and computer activity;
If the problem is clearly linked to movement (eg. vibration, or tilting the screen) that proves it is a hardware problem, then it is a matter of narrowing down and isolating the faulty component.
If it is definitely linked to computer activity, so for example it occurs whenever a usb device is activated or something processor-intensive is run, then it could be a problem with the motherboard.
Sure, the inverter could be intermittent, but I think that is unlikely given the function of an inverter.
More likely in my opinion is a worn out cable, especially in a laptop screen assembly which hinges.

I think it is unlikely that is is a software problem of any kind (and just to clarify, I mean software not firmware), but given the OP's sentence;

it's fine when use the restore disks

I would suggest ruling out software by trying a live cd, before touching any hardware.

Please, if you disagree with anything I have said challenge it using all of your knowledge, do not assume I know nothing and simplify it.

Thanks,
Andrew

It should be clear I don't assume. And I was not patronizing you. You presented some incorrect information. You have since clarified that, and I appreciate it.

@The Cardinal, you said,

I then thought it might be the backlight or the cable connector. Don't think so, because as I said above, it's fine when use the restore disks. In fact, provide I don't do anything other than move the pointer around the desktop, all appears to be well.

This does throw a kink in there. If you boot into the BIOS Setup Menu, is the screen is nice and bright?

Hi again Gentllemen.
Thanks for both of your advice - and I hope no long standing friendships have failed here!

I've replaced the screen inverter but I still have the same problem. I also have an additional problem and that is that the laptop occasionally switches itself off, usually after the desktop has populated up with all the icons, but occasionally after about ten minutes or so.

I'm starting to wonder whether or not I have a virus onboard. With this in mind, I burned off a system erase cd from Webroot's Window Washer. The idea was that if I clear the hard drive it would clean uip anything nasty that I'd picked up. Although this autoruns ok, it freezes when it presents its first menu asking what language I want to select. By freeze I mean I can't move up and down using the keyboard keys and pressing "enter" has no effect. Once I've got to this stage, the only option to press the off button.

I've also notice that when I enter the screen that gives the option for starting in safe mode, starting in last configuration of Windows that worked etc, I have the same problem - that is I can't move up and down the options using the keyboard and "enter" has no effect.

Any further help will be gratefully received.

Regards

Don't worry no friendships broken, I'm new to these forums and possibly reacted a little too harshly.

You have replaced the inverter already? That was fast. I wouldn't have been so quick to spend money on new hardware without a certain diagnosis first.

I still think this part of my post is crucial to diagnosis:

Does the backlight switch on and stay on as normal if you don't boot windows?
For example, if you open the BIOS settings as soon as you switch it on, or boot into a live CD like Knoppix Linux. (you can download the disk image here: http://ftp.uni-kl.de/pub/linux/knopp...7-01-04-EN.iso)

Digerati also mentioned the BIOS - as it is not affected by any software, it will show whether you have a hardware or software problem. (A virus is a software problem, as it runs only once windows is running)

-Andrew

It seems to me that you have a whole host of problems. The lighting could have been a dying graphics chip (the GPU) not being able to provide the correct graphics when you where telling it too. I don't think that I put that the best way but do you understand what I mean? I suppose that I mean the the GPU can't keep up with the demand on it. The keyboard problem makes it seem to me that you either have a problem with its cable or the, combined with the graphics problem, a motherboard issue which could be the chipset since it controls both. I suppose that it could also be that power supply isn't providing enough power but I'm more inclined to a MB problem.

Either you have have several smaller issues or one larger issue so perhaps it would be best to take it to some technicians as they can run some tests that you can't. But lets wait for Bill's take on this. You do have a complex case.