Is this a CRT (glass tube) monitor?  How bright?  Just a blank white screen?  Or does the original display brighten to where it's distorted ('blooming') with diagonal lines appearing where they weren't before?  Do you have another monitor to try?  How about another display card?

 

You'll have to substitute known-good parts (monitor, card) to narrow it down.  At this point it could be anything.  Monitors, display cards, motherboards, power supplies, peripherals can cause this.

 

You might try removing existing accessory cards to eliminate them as the cause.

Yes, the computer went dead the second time also. The monitor is a Dell flat panel.

It's been on a couple of hours now and hasn't repeated behavior.  

Just crashed for the 3rd time. I'm not a techie and this seems like it's going to be a tough one to figure.

 

So, if it's not the monitor, then it could be the video card or something on the motherboard? Is this something that can be tested with the right tools?    

Monitor should not be capable of crashing computer.

 

Along with the 'blue screen of death', there are black SODs and white SODs.  Display card, other plug-in cards, chipset (motherboard) need to be eliminated by substitution or removal.

The method is to substitute questionable parts with known-good ones.  Doesn't take much more than a Phillips screwdriver to dismantle a Dimension.

 

If you have a video card, remove that and connect to onboard video (under plastic cover).  If it never quits in that configuration, buy a new video card or continue using onboard.

 

If it still quits, it could be another plug-in card, power supply, motherboard, in order of cheapness and ease of replacement. 

 

 

Looks like we may have a figured out the problem. The last time it crashed, the monitor light was still green indicating that the video card was still sending a signal. Also, although the screen was black, apparently the computer was still operating. So we pulled the monitor plug out, put it back in and the screen displayed normally.

 

I'm not 100% sure but it seems that the monitor tube(?) might be going kaput. I swapped in another monitor and it hasn't failed yet so maybe it was just the monitor.  

Thanks for your input guys.

 

Bob   

I am having the exact same problem with my display going black on me.  Put a test monitor on the computer using a different port and that display also went black.  Spent 5 1/2 hours on phone with Dell tech in INDIA.  Pulled video card, pulled all other cards, even pulled and tested each stick of memory to try to isolate the problem.  Plugged monitor directly to video port on motherboard.  Still had failures with nothing but a memory stick plugged in.  They sent a tech out today with a new motherboard.  He installed it and thought all was well then 10 minutes after he left the monitor brightened and immediately went black.

 

I have found that at first I could unplug the connector from the back of the flat panel and then plug it back in and I would have a few seconds to view the screen but even that isn't working now.

 

I believe the problem is the computer, not the screen but even the tech doesn't seem to know what the problem is.  Any more suggestions?

Can only go over what's been done, and speculate from there.

 

Everything in the direct video path has been substituted, removed or replaced--monitor including monitor cable, connector at computer end, all accessory cards including display card, memory, motherboard.

 

That leaves power supply and CPU.  CPU doesn't manage video directly, and the parts of the chipset that do have been replaced.  Gain is dependent upon voltage so a power supply overvoltage condition might account for the brightening.  Under this scenario though, overvoltage should be 'crowbarred' which would shut down the supply and make the power light yellow.  If the overvoltage were small and not enough to trigger the crowbar, normal operation should continue (albeit at reduced reliability).

 

First thing I'd do is substitute another power supply.  Call support back, I suspect that's what they will do.  Can't say what the outcome will be though, this is not a 'routine' problem.