Dual Screen pc Display Glitch
January 9, 2012 6:54 PM   Subscribe

I have a dual screen pc display problem that I'm having trouble diagnosing.

I have an October 2009 store-bought, out-of-the-box Compaq pc [AMD Athlon IIx4 620 Processor 2.6 GHz || 4 GB RAM || 64-bit OS] with 200GB free on a 500GB hdd.

I've had dual monitors about 18 months with zero problems prior to a month ago : an old Dell 17" that is fine and a Samsung 23" [model LS20AQ....] that has been "playing up" in this last month.

I've never noticed any hdd problems but the tower sits on (a cardboard sheet) on the floor of very old, dying carpet. I vacuum regularly, am careful to do the spaghetti and the pc and its intakes/fans and open the box about 3 times a year and carefully clean. The disc drive has made no weird noises, beyond the odd fan speed change that's not really anything I'm sure, and I don't think I've had any other problems at all with the software or hardware since purchase.

Just by the by, I've had a 1TB ext drive hooked up for about the same amount of time that the screen has been playing up. I don't see a connection between the two : it feels like a coincidence and I may even be wrong on the dates. Note: it's not an actual backup drive with its own software; it's just storage and I backup once a week using the Win7 software in Control Panel.

OK.... there are 2 plug holes for monitors on the back of the pc necessitating that the Dell connects to the tower via an adaptor (no biggy). The Samsung connects to the pc directly via the regular ummmm.. whatever it is... 16pin plug or whateveryoucallit. The screens have always worked this way without problem before last month.

What happens is this... (& this is only approx description in a lot of ways. I didn't take a lot of notice to begin with; I was just trying restarts etc really fast just to get the bloody thing on so I can't vouch for certain as to all the ways the problem has manifest itself)..

I start the pc and turn on the main Samsung monitor and .... nada. There appears to be no signal reaching it (the intermittent blinking of the power light continues unchanged; whereas it stays continuously blue when a signal is received).
If I turn on the Dell monitor, sometimes (often?) the startup screen appears and I can put in the password and it will boot properly but at other times that screen also remains blank. Sometimes all the main screen folders end up on the Dell and the main screen (in Screen Resolution) has been changed without my help from the Samsung to the Dell.

I have often just turned the machines off at the wall if I can't access a restart link from the Dell monitor and basically keep rebooting (often 4, 5, 6 times and getting longer now) until the screen appears in the main Samsung monitor. Occasionally the screen appears ok in the Dell and then automagically appears a couple of minutes later in the Samsung. In other words, there are erratic profiles of symptoms that appear in a kind of random way; or, at least, as random when there's a finite number of screens and manifestations of problems.

I have just now (finally : it's been a weird problem and I'm bloody lazy!) swapped out the Samsung monitor for a ViewSonic monitor of about 21" and approximately the same thing happened during booting : nothing on the ViewSonic for the first few boots, the main screen changed to the Dell and all the regular desktop folders moved over to the Dell.

So it would seem (to me) it's not the hardware.

Please note that I am what you might call "fair" in terms of being technologically capable or proficient. Don't be thinking that I have tooooooo much knowledge though.

I don't believe I've added any or much new software in the recent past. I have MS Security Essentials running all the time and I'm fairly careful about what torrents I d/load. CCleaner runs on startup; I also run SuperAntisypware from time to time.

In case it wasn't clear, the dual screens are maintained via "screen resolution" from R-clicking on desktop. In that window I choose landscape display and "Extend these displays" and use the recommended resolutions for each screen's display attributes.

So yeah... does anyone have any idea how I might go about diagnosing this problem and, if we just accept that I can follow orders but probably not toooo much else if it gets esoteric, what I might do to rectify it ?????

Please let me know if I haven't supplied all the relevant info. I can't think of anything else program-wise that seems relevant from the last month at any rate. [if you want details on the graphics card, please tell me how to find them]

posted by peacay to Computers & Internet (13 answers total)
It sounds to me like your video card is dying in an intermittent way. Any way you can get your hands on a spare/different video card, swap it out, and see what happens?
posted by Betelgeuse at 7:08 PM on January 9, 2012

Best answer: Try shutting down the PC, then turning PC and both monitors off at the wall switch rather than using their inbuilt power controls. Leave things that way for at least 30 seconds to make sure everything's standby power has had time to die. Then turn on the wall switches for both monitors; then turn on the wall switch for the PC; then start up the PC.

Once it's started, hold down the Windows logo key and press P. You should see this "Connect to a projector" prompt and you should be able to cycle through various combinations of your two screens using the left and right arrow keys.

My rationale for the power switch dance: Modern display monitors have microprocessors inside, and sometimes these can get hung up, which makes the monitor go completely unresponsive. In some monitors, this unresponsiveness extends to the facility that the computer uses to detect that the monitor is present at all. Hard power cycling is generally enough to fix this. Also, some computer BIOSes will only enable display hardware for monitors that they see connected during power-on self-test, which means that Windows will never see a monitor that gets connected late.

If this works, then before you decide there's an actual fault needing further investigation, you should get in the habit of making sure both your monitors are powered up before you start your PC. This should at least make things behave consistently.
posted by flabdablet at 7:20 PM on January 9, 2012

Response by poster: Thanks.
flabdablet, I understand what you say, but I turn the whole lot off at the wall very regularly in the "dance" to get the display happening. I'll have another go at doing that later (have stuff going that I can't turn off for a few hrs) but I don't know that it's that. I am open to being wrong but my guess is that it's morelike what Betegeuse surmises: that the video card is on the fritz.

I don't have access to a spare card (but now know - or have relearned - what it is!) but note that the ATI Radeon HD 4350 in this pc is a budget piece and is not rated well on performance.

So unless someone comes up with (a) better alternative(s), I'll try the power option of flabdablet later on and if it doesn't work, I'll have to think about what to do. Might be best to take the tower to a pc shop rather than just buying the new video card on spec, so to speak.

Any other thoughts, recommendations??
posted by peacay at 7:53 PM on January 9, 2012

I turn the whole lot off at the wall very regularly in the "dance" to get the display happening

Then I suspect even more strongly that the problem is due to the PC not detecting monitors as it comes up, which in turn is due to PC standby power coming alive before monitor standby power. After they've all been off at the wall, try applying power to the monitors first.
posted by flabdablet at 11:56 PM on January 9, 2012

Response by poster: --try applying power to the monitors first--

Umm. Not sure how to do this in a practical sense. It will, I guess, mean getting another extension lead and another power board as everything is, at present, powered from the one outlet. (there's another outlet adjacent to it but, as I say, will need more leads to be put in use) == I will have to go shopping in the next day or so I suppose.

So, if this works flabdablet, what does it augur for the future ? Why is it happening now and is it going to require booting/powering up in this specific way all the time in the future?? Are there other underlying problems??
posted by peacay at 6:33 AM on January 10, 2012

I'm willing to bet your Samsung is on the DVI output and the Dell is on the VGA. There's some lag on bootup and VGA is detected faster, therefore it's set as the primary display until windows boots and takes over that setting. Are you running these in "clone" mode, or "stretch my desktop" mode? I have the same issue, but it usually resolves after bootup is complete.
posted by cosmicbandito at 8:37 AM on January 10, 2012

Not sure how to do this in a practical sense.

If your PC power supply has a switch around the back, near where the cable comes in, that's a hard power switch; turning that off has the same effect as turning off the power at the wall. If it doesn't, you can always unplug the power cable from the back of the PC before turning on the wall switch, then jam it back in after the monitors have powered up.
posted by flabdablet at 9:21 AM on January 10, 2012

cosmicbandito, if the Dell were on the VGA output it would likely not need an adapter. I'm guessing that both monitors are in fact being driven via VGA, which the Dell is getting via a DVI-I to VGA adapter.

If things get really desperate and you have a spare VGA cables you can afford to butcher, one rather agricultural but effective way to deal with Windows 7 monitor connection problems is to break off pin 12 inside one end of the VGA cable supplying the secondary monitor (this is fairly easily done with a pair of fine point pliers).

This makes it impossible for the PC to interrogate the display to find out its make and model and supported resolutions, and disables Windows 7's hot-plug display detection. Windows will treat any display so cabled as a generic analog video display, and run it at 1024x768 by default. The nVidia graphics control panel has a feature called "rigorous display detection" that you need to exercise before Windows will see a second display if it's cabled this way; I imagine the ATI drivers would have something similar.

Because Windows has no idea what kind of display it's dealing with, it won't limit the resolutions or refresh rates you can set on it - all become available. It also won't arbitrarily decide to rearrange all your desktop icons. And it won't be able to power down the display, only blank it.

I've had to do this to the VGA cables supplying the data projectors at school since we started using Windows 7 PCs to drive those. The cables involved are long (5 or 10m) and although they deliver high-quality video, they're apparently susceptible to noise pickup on the monitor ID/control lines as these don't use differential signalling. With Windows XP, this caused occasional non-detection of a data projector, requiring a restart to fix; with Windows 7, which apparently polls its display connectors every few seconds, it caused frequent cycles of display disconnection and reconnection, making the PC almost impossible to use.

It gives me the shits that there's no software method for turning off Windows 7's display ID polling, but there it is.
posted by flabdablet at 9:47 AM on January 10, 2012

Response by poster: OK, well, with a single data point to go on, you're 'turn monitors on first' idea worked flabdablet. Thanks very much.

The pc doesn't have a power switch on the back so I'll have to get an ext cord and power board but that's no sweat.

I'll probably swap out monitors and change the power board in the next couple of days and I'll report back as to how it goes so don't flip this out of recent activity just yet. [I might refrain from modifying the VGA cable for the moment though.]
posted by peacay at 3:32 PM on January 10, 2012

Response by poster: Things appear to have become either more clear or more complicated.

That single data point above (*moment of success*) referred to the 2 smaller screens working harmoniously. In other words, the regular large Samsung screen had been swapped out last night.

When I tried to put the Samsung (large) monitor back into the setup, taking out the old Dell 17" and substituting the ViewSonic as the 2nd monitor, try as I might, I could not get the Samsung screen to work, no way no how. And yes, I followed the powering on/off sequence you outlined flabdablet.

While I was trying various combinations to try to get life out of the Samsung, I did notice that there was an intermittent - very slight amount of - "light" appearing on the Samsung screen which tends to suggest to me that the problem is more likely the Samsung screen itself (I had also swapped out the VGA cables and got the same appearance).

So now I've got the ViewSonic as No.1 screen and the Dell as No. 2 screen and there's zero problems at all. I'm about 99.79% sure that the Samsung warranty has run out. Bugger. I guess I might take it into a shop to see if they can test it.

Thanks again.
posted by peacay at 10:57 PM on January 10, 2012

Sounds like the Samsung has an intermittent power supply fault.
posted by flabdablet at 4:34 PM on January 11, 2012

Response by poster: I ended up getting a new 24" LG screen on special locally today for <> I'll still prolly take the Samsung into a shop if they can test it cheaply to see if there's anything worth salvaging.
posted by peacay at 9:31 PM on January 11, 2012

Response by poster: err. that is less than $200
posted by peacay at 9:32 PM on January 11, 2012

« Older Computers for Dummies for Dummies   |   Help me find a good travel agent Newer »
This thread is closed to new comments.