QUESTION: This may not be a monitor problem per se, not sure. A couple of times now, after my computer has been on and the monitor is working fine, I'll come back to the computer to see a black screen and 'no monitor signal detected.' I check the monitor connections and all are secure. After shutting off the computer manually (because the screen is black and there is no mouse pointer), the signal to the monitor is restored. Any idea what could cause this? Thanks
ANSWER: The issue here is likely that the computer itself has crashed and is no longer sending a video signal to the monitor, not that the monitor itself is at fault. When this happens, is the computer still visibly "on?" (e.g. fans running, lights on). What operating system does the computer run? What do you know of the machine's hardware specifications?
Generally these kinds of crashes are either the result of the operating system failing (not that the operating system is completely broken, but that its encountering a fault condition while the machine is idle and crashing), or hardware issues within the machine. However, because you've only noticed this as an intermittent issue, it's somewhat harder to diagnose. Knowing more about the computer will help me get a better idea of where to direct you for troubleshooting.
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QUESTION: This is a Dell 'Dimension 2400' desktop that is quite old. The OS is Windows XP. Both times this has happened I wasn't at the computer so didn't see it actually happening, but when I came back to it, saw the monitor status as 'no signal.' The computer was on, fan and lights running.
Hope this help too, thanks.
Processor Intel(R) Pentium(R) 4 CPU 2.80GHz
Processor Speed 2.72 GHz
Memory (RAM) 1536 MB
Operating System Microsoft Windows XP Home Edition
Operating System Version 5.1.2600
This is not an entirely uncommon (not to say it's a world-wide problem) with the older, entry-level Dell desktops (such as the one you have). Unfortunately, said desktops use a number of proprietary (and therefore suitably obnoxious to replace) components (the power supply being the worst offender). This will heavily limit your options for hardware replacement (more on this in a moment).
However, we can still check the system memory for problems using memtest (http://memtest86.com/
- its free); you'll burn a bootable CD and let this run for a number of iterations, the goal is zero errors (if you can, let it run for a full 24 hours). If it produces errors, the system memory is likely your culprit.
We can also look at software as a culprit - my first question would be: is Windows as up to date as is possible? From there, are you using a competent anti-virus/anti-spyware suite (Windows Defender and Microsoft Security Essentials are worth the (free) download if you don't have such protection), and is it up to date, and do scans of the system return no results? Beyond that, ensure that drivers for your primary devices (motherboard, graphics adapter, audio controller) are as up to date as possible (which will likely mean driver packages that are a few years old, given the age of the machine). I'd also suggest taking a look at recently installed applications (if you can trace this crashing to a specific point in time, and you installed a software application before the crashing began, it might be worth looking at that application) - what kinds of programs are running in the System Tray or starting with Windows? (Do you have a lot of background applications, basically).
If none of those avenues return something bona fide, reformatting and re-installing Windows is likely to resolve any potential software errors, but can be a very time intensive process, especially if you're starting from relatively old installation media (as you will have to download many updates for Windows). Alternately, depending on the graphics hardware installed in your machine, upgrading to a newer version of Windows (such as Windows 7) would be possible (the Pentium 4 will handle it), however this is not a guarantee that something is not wrong with the underlying hardware (which is, unfortunately, "locked in" to the machine).
Overall, due to the proprietary nature of a few key components within the machine, it may be worthwhile to consider looking at a replacement computer and simply ferrying your data over to that.
If you have further questions, or need clarification, feel free to ask.