Regular TV on its side

jot3

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This has probably been asked...

1. Why do you get rainbows when you turn a regular TV on its side?
2. Can you prevent rainbows with regular TVs if you want to mount them vertically?

Thx!

jot3
 
The Earth's magnetic field affects all CRT's. As you change the orientation of the tube, it interacts differently with the static magnetic field of the Earth, and throws off the purity. This happens every time you move a TV, pretty much. To counteract this, ALL color monitors and television sets have built in degaussing coils. They're powered by a thermistor, and as such, fire for a short time every time the set is turned on from being cold, then go inactive. They won't fire again until the thermistor cools down again.

So, to prevent the "rainbows", turn the TV on it's side first. THEN turn it on. It may take an additional power cycle or two to get it all cleaned up from rotating it that much, and occasionally you need a standalone degaussing coil to clear it up. But, usually, if you let the thing sit for a half hour, then turn it back on, it should be fine.

The "rainbows" aren't hurting the TV in any way. You'll see the same problem if you open or close a cocktail game while it's on, or even turn many games/TV's to face a different direction while on. Letting the set degauss (or doing it manually) will fix it up.

Computer monitors have a degaussing switch or function in the control panel that allows you to fire the degauss circuit at will. Try this at work - turn a co-worker's computer monitor sideways, screwing up the colors. Then degauss it with the front panel control, which will fix it. Then rotate it back upright into it's normal position - which screws up the colors again. Walk away. :)

-Ian
 
follow up

So my follow up question is...

Why can you rotate an arcade monitor and not a regular TV?
Wondered if you could do something to prevent the TV....
 
so how can a game like pacman have a monitor that sits in there for years and you never see it make weird rainbow colors?

not trying to sound like a turd...i'm really trying to figure this out. Seems like there are lots of monitors that can sit vertically in the arcade world without a problem, but as soon as you turn a normal TV on its side, it gets all discolored (rainbowed) and looks like crap.
 
I should probably elaborate as to the cause of this. Inside the glass of the picture tube, just behind the faceplate, is a metal mesh with holes in it, called the shadow mask. This is in place to prevent the electron beams from hitting more than their intended spot on the tube. The Earth's magnetic field will actually slightly magnetize the shadow mask inside the picture tube. As you move the tube through the magnetic field lines of the Earth, this causes the mask to become magnetized. As the electrons pass through the shadow mask, they get slightly deflected by the magnetized mask, and this causes them to miss their mark, and hit the wrong colored phosphor stripe on the face of the tube.

Degaussing is simply the process of demagnetizing this shadow mask.

And yes, arcade monitors are just as subject to this as TV's - turn a horizontally mounted montior on it's side, and it'll be "rainbowed" until it's degaussed. Once the shadow mask has been demagnetized, the picture will be fine. As this degaussing phase happens every time the set is turned on, once it's in place, it tends to stay looking correct.

The problem is more apparent because rotating a monitor 90 degrees like that creates more magnetism on the mask than most other things do, so sometimes it takes a couple cycles of the set's built in degaussing function to clear it - or a manual degaussing coil.

-Ian
 
now its making more sense

Ok,

This is making more sense. So in theory, if I turn my monitor on its side and degauss, it should remove the rainbows. I shall try! I have a couple older 21" mac monitors that I want to put to good use by making them vertical since I'm without a real arcade monitor.

;-)

Thx!
 
So in theory, if I turn my monitor on its side and degauss, it should remove the rainbows.

Exactly. Not just a theory - that's how it works :)

You can do it with a television too, just, without a manual degauss button, you have to turn the TV on it's side first, THEN plug it in and turn it on. Might take a couple of those cold poweron cycles (let the TV sit for a half hour or so) to get it cleared up completely.

-Ian
 
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