Question about Standard (CRT) Televisions

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Colourful picture We have a circular rainbow of colour all the time. I've checked the plugs in the back. Any ideas if it's terminal? It's only two or three years old

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Discoloration of this sort is caused by magnetism. All CRT TVs (like yours) have a de-gaussing coil around the picture tube that de-magnetizes the screen (more specifically the shadow mask) every time you turn it on. It is likely that the circuit that controls this coil is at fault. There is probably a cold solder joint where it connects to the main circuit board.

The other scenario is that someone (small child generally) has run a magnetic object very near to the screen, magnetizing the shadow mask (inside the picture tube) and causing a rainbow effect. This is less likely if the rainbow effect is a nice even circular shape. Generally if it's been magnetized by a magnet as described the discolored areas will appear blotchy.

In short, if you have some electronics skills, get in there with your soldering iron and touch up the connections to the de-gaussing coil. If not, find someone who does.

Posted on Oct 02, 2008

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1 Answer

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Hello
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It is very difficult to detect the loose soldering by ***** eye, as it will be microscopic in nature. It is a best practice, to resolder most of the solder terminals of that board, by app;ying a little more solder, whout making any solder bridge in between adjecent solder terminals. This will solve the colour problem to your TV.
I've attached a picture of a tV with back opened. You can see the Video Output Board pluged on to the back of the picture tube. Just resolder all the picture tube base socket terminals solderings also. OK


gopakumarg43_35.jpgHere the main board has been pulled out and placed vertifally at service position. The CRT board [video output board] can be located as you open the TV.

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