[PLUG] OT: EM-Damaged Display

Rogan Creswick creswick at cs.orst.edu
Fri Feb 14 09:53:02 UTC 2003


I had a similar problem at work a year or so ago, every spring some of
the monitors would start to flicker, after a few months it would go away.

Half the people in the office had mini-fans mounted on their back cube
walls, which were only in use during the hotter months, everyone else
had flickering monitors. 

It may be worth asking your friends explicitly if there have ever been
any electric motors in that part of the house / lot.

-Rogan

On Thu, Feb 13, 2003 at 09:01:45PM -0800, Dylan Reinhardt wrote:
> Hi all,
> 
> This is a bit off-topic, being a hardware / physics question... but it's 
> something I thought y'all might enjoy chewing on anyway.
> 
> About 18 months ago, some friends of mine got a new PC from a local vendor 
> I recommended.  The display was a good quality 17" CRT (AOC Spectrum 7GLR).
> 
> After 8-9 months of unblemished operation, the display started showing huge 
> amounts of distortion in large, wavy, occasionally-changing horizontal 
> bands.  It looked for all the world like some kind of electromagnetic 
> interference.
> 
> I poked my head out the window and sure enough, their satellite dish was 
> mounted on the outside of the house, maybe 2-3' from the back of the 
> display.  I had taken a different display over for testing purposes and 
> when I plugged that one in, everything worked fine.  I decided I was wrong 
> to suspect the satellite dish.  The problem -- whatever it was -- must have 
> been the display.  That opinion was supported by the fact that the problem 
> persisted when I plugged the first display into a PC back at my office.  I 
> sent it back to the manufacturer and received a replacement, but no 
> explanation.
> 
> Fast forward another 8-9 months and now the replacement display (also a 
> CRT, but different model) is showing very similar problems and I'm thinking 
> I might have been right about the satellite dish in the first place.  I 
> have installed dozens of these displays around Portland and have never seen 
> anything like this anywhere else.
> 
> At this point I have to admit I'm way out of my league.  Some questions 
> come to mind:
> 
> 1. Can there possibly be any such thing as cumulative damage from EM 
> interference?
> 2. Could the satellite dish be a red herring?
> 3. Will a gaussmeter help me diagnose the problem or find a better spot for 
> the computer?
> 4. Might an LCD display survive any better than a CRT?
> 5. Is there any kind of low-cost shielding I could be using here?
> 
> Since I never got that EE degree, I'm at a bit of a loss... any thoughts or 
> help would be greatly appreciated.
> 
> Thanks in advance for anything offered,
> 
> Dylan
> 
> 
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