Symptoms

You can experience wavy or flickering or jittery video on a Video Graphics Array (VGA) Connection. Where a monitor or a projector is connected to a laptop powered through an external AC adapter. A VGA connection uses an analog signal to transmit data from the laptop to the display. This is considered as a legacy type connection and is more susceptible to interference in the data transmission. (Newer digital connections like High-Definition Media-Interface (HDMI) and DisplayPort (DP) do not have this issue.) Testing for the existence of a ground loop is a likely cause of electromagnetic interference (EMI). This EMI can be interfering with the video signal to your external device.

Cause

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Resolution

Use the following tests to determine the issue: Ensure that you are using the latest revision of the AC adapter that is available for your laptopTest with both a three prong AC adapter and a two prong AC adapter (if possible)Test with a grounded AC plug adapter 3 prong to two prongs (if possible)Test with a double or triple shielded VGA video cable (if possible) Search for a shielded VGA cable on Dell.com or Google.com to bring up several examplesTest with a digital video connection (if possible) For example: Digital Visual Interface (DVI), DP, or HDMI)Test with a ground loop isolator (if possible) Useful Links Ground loop problems and how to get rid of them: https://www.epanorama.net/documents/groundloop/ What is the problem in grounding systems used in buildings? https://www.epanorama.net/documents/groundloop/electrical_wiring.html 

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