Flex your VGA cable and see if that corrects it. Most of the time it will be the VGA cable wire bundle. They are pretty fragile and tend to break and stretch over time. If you have a separate cable, such as you find on most newer LCD monitors, buying a new one will solve the problem, but if this is a Tube type monitor the cable is permanently attached and unrepairable.
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Flex your VGA cable and see if that corrects it. Most of the time it will be the VGA cable wire bundle. They are pretty fragile and tend to break and stretch over time.
If you have a separate cable, such as you find on most newer LCD monitors, buying a new one will solve the problem, but if this is a Tube type monitor the cable is permanently attached and unrepairable.