Probably the PC supply is grounded just by the MB screws to chassis, which is not really a positive bond to system ground, who know what it is floating at?
With PC based systems, I make sure the PC PS common is bonded as close to system ground as possible.
Al.
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CNC, Mechatronics Integration and Machine Design.
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E. |