Maybe a power problem with the supply for the display's backlight? Perhaps it's going bad and can only light up the back panel for a few seconds then turns off, the image may still be there but you can't see it because the backlight isn't working anymore. Just an idea.

Not a driver issue but a hardware issue and given the age of the laptop and that it likely has a lot of hours by this point chances are the backlight is going out or the inverter is kicking the bucket. These things can work for a few seconds at a time then die again till you power cycle again, ran into the same problem with one of my machines and found that it was the CFL backlight had burned on one end.

You might well be right, but I did try the laptop in darkness though, to see if I could see anything at all on the screen (since, in the darkness, even the very tiny amount of light the back-light-less screen would put out might be visible), but I couldn't see anything, so I don't know. I should have said that in my original post, sorry.

Edit: I've just tried a universal power pack on the laptop, in case the existing power pack was the cause, but even with the universal one, the laptop behaves exactly the same, so it's not that.

That won't work. A LCD by itself does not emit ANY light. All it does is modulate the light that goes through it. If the backlight doesn't function at all you'll see less in darkness. I suggest the opposite, shine a bright light at an angle on the screen and see if you can distinguish anything on it while it's on.

stamasd wrote:

That won't work. A LCD by itself does not emit ANY light. All it does is modulate the light that goes through it. If the backlight doesn't function at all you'll see less in darkness. I suggest the opposite, shine a bright light at an angle on the screen and see if you can distinguish anything on it while it's on.

Oh right, I didn't know that. I'll try what you suggest tonight, when I get home.

My first guess would be that there is something wrong with the inverter supplying power to the LCD; although normally I would expect that, if it's broken, you will have no backlight, ever, I don't think it's unheard of that a dying inverter would be able to power the backlight briefly for a few seconds, before going out.

However, as you mentioned that you also have a problem with the lid close switch, I suspect that that is actually the culprit: it must be permanently stuck on "lid closed". Even if the system is configured to "do nothing" upon lid close (not standby, nor hibernate), it still turns the display off. It is also conceivable that the logic to do so does not kick in until the laptop has been on for a couple of seconds, which is why you would still see the logo.

The switch on these laptops is mechanical, so first check if it might be physically broken or something is jammed in there, which prevents proper operation; if mechanically it responds fine, but still does not trigger any action (and the display is always off), then it would be time to check the circuitry (not that I would know how to go about it).

stamasd wrote:

That won't work. A LCD by itself does not emit ANY light. All it does is modulate the light that goes through it. If the backlight doesn't function at all you'll see less in darkness. I suggest the opposite, shine a bright light at an angle on the screen and see if you can distinguish anything on it while it's on.

I tried it, but I couldn't see anything, though I can't say for definite if that's because there really is nothing there, or if I just couldn't see it, sorry.

dr_st wrote:

My first guess would be that there is something wrong with the inverter supplying power to the LCD; although normally I would expect that, if it's broken, you will have no backlight, ever, I don't think it's unheard of that a dying inverter would be able to power the backlight briefly for a few seconds, before going out.

But it does seem strange to me that the Compaq Logo (red on black, with white text text) is always perfectly legible and the same brightness (as far as I can tell) every time yet then nothing, even as presumably the problem would be getting worse if the backlight is somehow getting worse over time/reboots. Not that I know anything about the technicalities, of course.

However, as you mentioned that you also have a problem with the lid close switch, I suspect that that is actually the culprit: it must be permanently stuck on "lid closed". Even if the system is configured to "do nothing" upon lid close (not standby, nor hibernate), it still turns the display off. It is also conceivable that the logic to do so does not kick in until the laptop has been on for a couple of seconds, which is why you would still see the logo.

The switch on these laptops is mechanical, so first check if it might be physically broken or something is jammed in there, which prevents proper operation; if mechanically it responds fine, but still does not trigger any action (and the display is always off), then it would be time to check the circuitry (not that I would know how to go about it).

That's a great idea, I'll check the switch tomorrow (the laptop isn't here with me now). But yes, checking the internal circuitry would be beyond me too.

dr_st wrote:

However, as you mentioned that you also have a problem with the lid close switch, I suspect that that is actually the culprit: it must be permanently stuck on "lid closed". Even if the system is configured to "do nothing" upon lid close (not standby, nor hibernate), it still turns the display off. It is also conceivable that the logic to do so does not kick in until the laptop has been on for a couple of seconds, which is why you would still see the logo.

The switch on these laptops is mechanical, so first check if it might be physically broken or something is jammed in there, which prevents proper operation; if mechanically it responds fine, but still does not trigger any action (and the display is always off), then it would be time to check the circuitry (not that I would know how to go about it).

I've tried to check that, but I can't determine how the laptop tells if it's lid is open or closed. Does anyone know where/what the mechanism is on this laptop, please? I've tried pressing/touching everything that looks like it might serve that purpose, and I read online that some laptops have a magnet that serves this function, so I've ran a magnet around the lid and the keyboard half of the laptop, when the laptop was on (and not connected to the external monitor) but the screen never came on.

I've searched for manuals, and found a couple online, but I can't find anything in them that seems to be a lid closed detector switch thing, but I might well be missing it because it's called something professional or non-intuitive, like "folding case state detector", because why make it easy for the home-user? 😠

I'd be grateful if anyone who is familiar with this sort of thing could maybe search for information and tell me where the switch is, please? The laptop is a Compaq N610c, thanks.

I think it may actually be inside the base where the latches go when the lid is closed. Can't be 100% sure now, and it's unlikely I'll see my N610c in the next 3 weeks. 🙁

dr_st wrote:

I think it may actually be inside the base where the latches go when the lid is closed. Can't be 100% sure now, and it's unlikely I'll see my N610c in the next 3 weeks. 🙁

OK, thanks. I probably won't bother taking apart the laptop and looking for the switch component, as I probably wouldn't recognise it even if I did locate it. I've found that I actually prefer using the external monitor, as it's bigger screen makes it easier to read smaller text, and since I never move the laptop then it's no problem having the external monitor plugged in, so I'll probably just leave it as it is. But if you do ever find out where the lid switch is, then please mention it here, for curiosity's sake.

And thanks to everyone else too, for all of the help and advice.

So, it took me longer than I thought, but I got around to testing the N610c and I think I can confirm my initial assumption.

Your problem almost certainly has to do with the lid close sensor. The sensor is located, as I remembered, at the front of the base, where the left latch goes as you close the lid. On the attached picture you can see that the screen is off due to the small scissors I jammed in there.

Furthermore, when I turn the laptop on, while the scissors press down on the sensor, I get the exact same behavior you described: Compaq logo visible at POST, then screen turns off whether you enter the BIOS or continue the boot process.

So I would check if perhaps something is stuck there - try to push down that hole with something thin (emulating the latch action) - there should be a thin piece of plastic moving up and down as you do. If it's stuck in the 'down' position, it will behave as if the lid is closed.

Now, if mechanically there is no problem, but the sensor itself is defective / shorted, this may be harder to fix.