Fixing a Samsung CRT monitor.
The problem with this old Samsung SyncMaster CRT monitor was the colors displayed were incorrect. The monitor was not able to display the RED color. (September 7, 2009)
To determine exactly what signal are missing in the CRT, I made a graphic with Paint with three squares: One RED, one Green and one Blue. As you can see in the picture, the red color is completely gone. It shows only a black square, so that means there is no signal to the RED beam inside the CRT tube.
I was able open this Samsung CRT monitor and check what's going on inside:
The red signal comes from the connector directly to the board in the back of the display. I found that knocking gently the board the color comes again, so I guess there was a "cold joint" where the solder wasn't joining the component or connector correctly.
Carefully, as the display holds more than 70,000 volts at the flyback and CRT area, I was looking for the failure.
The VGA RGB signals goes
directly to the back board, so the shield needs to be removed.
A 40-watts iron is needed to remove the shield as it was fixed with some solder, then pry. The shield can be removed exposing the back board<./center>
As I was not able to determine exactly where was the problem, I started to apply a new solder to each connector for the red signal. Once I finished, I turned on the monitor and knocked gently the back board to see if the failure was fixed. I did use a wooden stick to knock the board.
I was lucky to get the monitor fixed. It was just a cold solder. In some CRT monitors this issue is caused by the failure of the filament inside the tube. When this happen, it is not possible to fix it unless the CRT tube is changed, but that will be a expensive repair.
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