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Registered Member #940
Joined: Sat Aug 04 2007, 03:43PM
Location:
Posts: 7
A friend of mine has a CRT monitor that has a peculiar problem: when he rotates it on its sides (that is, rotating about an axis perpendicular to the centre of the screen, the screen facing you), the screen seems to display the screen content in changing colours. For instance, on the first 90 degree rotation clockwise, the colours are shifted to yellow, then another 90 degrees makes it shift back to normal, albeit slightly magnetized (some purple blotches), then the next 90 degrees makes it shift to blue. I'm not entirely sure what could be causing this, and as I live far away from him, I'm not able to open the monitor to look at it myself. I'm wondering if anyone else here has encountered the same or a similar problem.
Registered Member #63
Joined: Thu Feb 09 2006, 06:18AM
Location:
Posts: 1425
This will happen to all CRTs -- they are 'tuned' to cancel out the Earth's magnetic field -- if you turn a CRT on its side, the field interferes with the tube in a way the designer didn't intend it to.
You can pitch monitors back and forth (to some extent), but as soon as you start rolling them, they'll muck up. For the same reason, we don't transport CRTs back and forth between the northern/southern hemispheres. I wonder if in Antarctica they mostly use LCDs now
Registered Member #940
Joined: Sat Aug 04 2007, 03:43PM
Location:
Posts: 7
Very cool! Thanks! It's strange, though. When I rotate my CRT monitor, the colour shift isn't the same - my friend's screen goes all yellow, for instance, where as mine will only change partially. Regardless, it's fascinating to observe how much of an impact the Earth's natural field has on the tube itself.
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140
During the early 90's 'low radiation' (or something like that) monitors became popular, the idea was to have a low radiated magnetic field from the deflection coils. When I first started installing them I found that orientation with respect to the earth's magnetic field had the described effect - this was with the monitors in the upright position. Try explaining to customers that the monitor they just bought can only be aligned North-South ! Later magnetic shields were added to mostly enclose the crt allowing moderate deflection fields with minimal disturbance by the earth's magnetic field.
I built a pair of speakers for 'home cinema' with two 10" drivers in each, each with a LARGE magnet. When the tv & speakers were along the South wall I needed about 4 feet between speakers and TV on the North wall I only needed about 3 feet. So even TVs are sensitive to the earth's magnetic field.
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Weird CRT problem
