Windows – What would cause ripple interference on a monitor display attached to computer via VGA

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What would cause ripple interference seen on on a display whereby the computer is attached to it via VGA?

By ripple interference I mean that the edges ripple and the display flickers. It is occasional and intermittent and it may occur for a few seconds to a little longer.

My set up – the problem is seen with a 2010 17" MacBookPro attached to a KVM switch via a DisplayPort to VGA adapter. 2 other machines are attached to the KVM switch.

The problem has only begun recently, up until then this arrangement worked very well. The other 2 machines (Windows 7 and XP-based) don't show this problem when they are using the display.

I don't want answers advising to move to a HDMI or DVI based KVM switch for 3 reasons: 1) because I am reluctant to make additional purchases and 2) this arrangement has worked well for at least 6 months now and 3) One of the machines only supports VGA.

So to recap, what would cause interference on a VGA signal? Could it be a hardware issue?

Best Answer

It could be poor grounding of the computer or monitor, cheap cables, cables not screwed on tightly, or the KVM beginning to go bad.

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