What is causing this inexplicable video problem with my monitor?
November 10, 2012 9:59 AM   Subscribe

What is causing the strangest video error I have ever come across?

My monitor gave me a "No Signal" message, which I assumed meant the computer had died (it was a Linux machine in the midst of a large compile) and so rebooted it. Still no signal. Hmm, maybe the machine died and it will now need to be reinstalled? Anyway, I change the cable over to my Windows Desktop. No signal. Aha! Faulty cable, I hear you say. I swapped the cable. Still nothing. Aha! Faulty monitor I hear you say. I swapped the monitor. Still nothing.

What the hell is causing me to have a signal failure between any machine and any monitor using any cable?
posted by dougrayrankin to Computers & Internet (16 answers total)
Maybe a loose connection and then bent pins. Then you bent the pin on the replacement cable?
posted by srboisvert at 10:08 AM on November 10, 2012

Response by poster: I'm now on to my third VGA cable, and yes, the power is on (hence I get the No Signal message).
posted by dougrayrankin at 10:10 AM on November 10, 2012

What kind of graphics card are you using? Maybe you need to reinstall the driver.
posted by phaedon at 10:14 AM on November 10, 2012

Response by poster: If it was a driver problem, I would simply be able to switch the cable to another machine (which I have) and that would identify a particular machine as the problem. If it was a driver problem, I'd at least see the BIOS screen.

I have two machines: A and B
I have two monitors: A and B
I have two VGA cables: A and B

The problem with No Signal started on Machine A with Cable A and Monitor A. I have since tried all sorts of combinations of monitors, cables and machines and No Signal is the one consistent problem across all.
posted by dougrayrankin at 10:17 AM on November 10, 2012

You mean you tried to connect monitor A to a second computer and it still didn't work? And monitor B didn't work on the faulty machine as well? If both were true, that would be weird.
posted by phaedon at 10:19 AM on November 10, 2012

If you've tried all 8 combinations, then you have an issue with more than one component.
posted by nat at 10:19 AM on November 10, 2012

Response by poster: I've ruled out a problem with the cable by taking the cable to another physical location and testing it, where it worked. I've bought brand new today a monitor, so that should work. What are the odds of two PCs both developing faulty graphics cards simultaneously when not physically connected, or running the same hardware or software.
posted by dougrayrankin at 10:22 AM on November 10, 2012

Response by poster: More info: The Windows Machine boots up fine (as evidenced by the sound of the Windows Login Prompt) and then if I press the power button it shuts down normally too.
posted by dougrayrankin at 10:24 AM on November 10, 2012

Response by poster: It gets stranger... I move the PC to a new physical location in the same room, and all works normally.
posted by dougrayrankin at 10:44 AM on November 10, 2012

New location, different wall plug?
posted by zug at 10:52 AM on November 10, 2012

Response by poster: Yep, and now it works again at original location... Random.
posted by dougrayrankin at 10:53 AM on November 10, 2012

Alternately, corrosion on one of the pins on the monitor, whereby moving it physically happened to make that pin connect.
posted by zug at 10:53 AM on November 10, 2012

Yeah, corrosion or another partial impediment to connection on the monitor pins. It's hard to get in there, you might be able to work a toothpick in to knock off whatever is stick inside there.
posted by zug at 11:57 AM on November 10, 2012

Although, since you say you swapped the monitor... You've got me. Glad it's working though.
posted by zug at 11:57 AM on November 10, 2012

No problem is solved until it is understood.

Conclusively eliminate ONE component. Doesn't matter which one. Working from there, conclusively eliminate one of the remaining components. Repeat until your confidence has increased on the suspected defective part and when you can make the problem move with the part, you have found it.

There are occasional dynamic factors involved in multi-part systems, such as tolerance stackups, etc. that all add in one direction, but they are usually pretty stable. Sometimes, there are problems which are time specific or location specific and hard to replicate.

Your problem is a little too odd to follow since I am not that interested from this far off, so I confess to having not reasoned through it much. The process I describe is kind of universal, though, and useful.

If you can't come to a conclusion, though, it's not fixed, it's non-repeatable (or unverified ) failure (which is what we called it when I was in the rocket business.) Your accurate notes are an open case to be expanded when more problems arise, so none of this is useless, it's just preliminary. Most problems eventually yield to a persistent foe, so keep shooting.
posted by FauxScot at 1:24 PM on November 10, 2012

A long shot, but: is all of your equipment on the same ground? I don't know that it'd be enough to cause "no signal" to appear instead of just interference, but ground loops etc. can sometimes be the source of really weird problems.
posted by caaaaaam at 7:31 PM on November 10, 2012

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