VOGONS


First post, by Kerr Avon

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I have an old laptop, a HP Compaq evo n610c running Windows XP, which I keep permanently on the kitchen table, and I use it as an ebook/comic/magazine reader. But now it's developed some sort of problem with the screen. When I turn the laptop on, it displays the Compaq logo and "Press F10 to change settings" (which is what it should display), but then the screen goes black, and doesn't display anything else ever, until I turn off the laptop, then turn it on, in which case it shows the logo screen, and then immediately after that the screen goes black and stays back, you don't even see the BIOS settings if you press F10 to enter them.

The laptop seemed to run otherwise, just with no display, so I've plugged it into an external monitor, and using the monitor, the laptop works fine (minus the laptop's own monitor, which stays black). When I boot the laptop with the external monitor plugged in, the external monitor shows the Compaq logo (which now doesn't appear on the laptop's monitor, which instead stays black from boot up) then the usual PC stuff as it boots up, Windows loads, and everything works fine. So the laptop is perfectly usable with the external monitor, but when I remove the external monitor of course, the laptop is unusable as the laptop's own monitor will display nothing except the Compaq logo screen when first booted up.

And when I try to get the laptop to use both the laptop monitor and the external monitor together, via the display settings menu in Windows, the laptop seems to think it is doing so, but the laptop's monitor stays black.

To my thinking, it can't be a driver problem, because it happens before any software is loaded (immediately after boot up, you see the Compaq logo then nothing else, not even if you press F10 to access the BIOS), it seems unlikely to be a screen problem because the screen does work properly for a couple of seconds for the Compaq logo (though maybe the screen is knackered, and can't display anything higher res than that now, or something similar), and I don't think it's the laptop somehow thinking it should immediately disregard the laptop screen and use an external screen as there's no setting in the BIOS for it, and the only way to toggle between them is by pressing FN + F4, which is a Windows program function, and should only affect Windows sessions, surely? I've googled, but as far as I can tell there's no setting that makes the laptop, immediately on booting, divert the screen display to an external monitor even if there isn't an external monitor present.

It's not a problem of course, I can still use the monitor when killing time, I'm more curious about the cause of the problem than anything else.

I should say, the laptop is permanently offline, and I've not put any programs or ebooks or anything on the laptop for ages, so I don't think it's malware-related (and I don't see how it could be anyway, since even the BIOS won't show up on the laptop's monitor, but only on an external monitor), the laptop has not been dropped (or even moved) at all, and only I use it. I've tried pressing FN + F4 at all stages of everything, but the laptop screen doesn't come on, and if I press FN + F4 when the external monitor is plugged in and displaying the Windows desktop, then the image on the external monitor flickers very briefly (as though a screen-wide area an inch or so high, flickers on the external monitor, the laptop's monitor doesn't change or show anything at all), but then there's no further change, the external monitor shows the desktop as normal, but the laptop's monitor remains back as it does all the time.

I've tried booting from a CD, and it's the same situation. The laptop shows only the Compaq logo, then stays black, even though the laptop boots the CD. If I plug the external monitor into the laptop, then the external monitor shows the CD booting and running fine. Whatever I try, the laptop itself seems fine, aside from the laptop's monitor.

The only other symptom I can find is that shutting or opening the lid no longer seems to 'register' with the laptop; the laptop has always been set to hibernate when the lid is closed (to save the PDF reader and/or ebook readers' in their current state to save me having to remember what was open and where), and come back to life when the lid is opened, and so far that's always worked. But now it doesn't, and when I go to the Power Options, and tell the laptop to hibernate when the kid is closed, it doesn't. If I tell the laptop to Stand By when the lid is shut, it doesn't do that either. The laptop doesn't seem to register when I open or close the lid anymore, which to me would suggest a hardware problem, which of course would go a long way to explaining why the screen always stays black, but if so then why does the screen always show the Compaq logo screen (except, of course, when the external monitor is plugged in).

Any help would be appreciated, thanks.

Reply 1 of 11, by stamasd

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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.

I/O, I/O,
It's off to disk I go,
With a bit and a byte
And a read and a write,
I/O, I/O

Reply 2 of 11, by nforce4max

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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.

On a far away planet reading your posts in the year 10,191.

Reply 3 of 11, by Kerr Avon

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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.

Last edited by Kerr Avon on 2018-10-14, 17:23. Edited 1 time in total.

Reply 4 of 11, by stamasd

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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/O, I/O,
It's off to disk I go,
With a bit and a byte
And a read and a write,
I/O, I/O

Reply 5 of 11, by Kerr Avon

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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.

Reply 6 of 11, by dr_st

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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).

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Reply 7 of 11, by Kerr Avon

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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.

Reply 8 of 11, by Kerr Avon

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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.

Reply 9 of 11, by dr_st

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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. 🙁

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Reply 10 of 11, by Kerr Avon

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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.

Reply 11 of 11, by dr_st

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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.

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