dust pattern (just curious)

[n00b]

Well this isn't really important but i've been noticing it for a while. On my Panasonic tv the dust always settles so 4 distinct rings of dust are formed on the screen (about 6cm in diameter). they are perfect circles and are formed a little way in on each corner.
What would cause these rings? At first i thought it was the coils which steer the beam but then realised this cannot be the case because of their positions and also they would not make such large even circles.
This pattern does not happen on the Sony crt.
Its probably a simple explanation but its a slow monday so i'd be interested in suggestions

[contrex]

Static electricity is what usually makes dust stick to things. CRTs are well known to build up a static charge on the face of the tube which will attract dust, but it tends to be evenly spread over the whole screen in my experience. Maybe modern tubes are different. Goes to look at 3 month old Hitachi. No dust. (Maybe you need a woman around the place?) My TFT pc monitor doesn't seem to attract dust like my old CRT one did.

[n00b]

heh heh, there is a woman around the place. it gets dusted but in between its clear to see the ominous 4 circles. I will take a pic tonight....

[zircon3035]

Hi,

The rings are left by the robot that picked up the c.r.t. in the factory. These use 2 or 4 suction cups that grip the glass, so that the c.r.t. can be placed into the cabinet. They are sometimes visible as a faint mark on the glass, but usually only become noticable when dust sticks to them.

HTH,

Ian

[n00b]

Thanks Ian but would these still be there after a few years and after cleaning?

[Henryslater]

It could be vibration - no seriously.

If you vibriate a sheet (metal or glass) and place a substance such as sand on it, the vibrations forms the sand into a pattern.

Who knows - fact stranger than fiction!!!!!!

[leamspaceman]

Originally Posted by n00b

Thanks Ian but would these still be there after a few years and after cleaning?

The robot theory is almost certainly the one. Sometimes these things need to be cleaned off with something more agressive than just a duster.

[hamster]

When the screens are hot the vacuum chuck scorches ever so little, causing the print-in.

Typically the tubes exit the fritting oven at around 150C.

[DRGL]

Originally Posted by leamspaceman

The robot theory is almost certainly the one. Sometimes these things need to be cleaned off with something more agressive than just a duster.

Can't see it i'm afraid-my Panasonic is over 10 YEARS old now-it's been cleaned god knows how many times. My Sony CRT which is just over a year old has no such rings. It's like crop circles
ps,there is usually a ring mark on the centre of the CRT-this is infact a mark from the device that is stuck to the CRT whilst being setup at the factory.

[n00b]

This is a bit late but i had to wait for the dust to build up. It isn't as bad as it looks, they are only so visible due to the flash.
Its only a bedroom tv so not too fussed since the picture doesn't look different below these circles, just thought it was interesting.