Ok, so it sounds like the plasma, the blue-ray player, and the power conditioner are not responsible.
Behind my other suggestions was the thought that one of your ac runs may be miswired, which at some point in the past may have damaged a part such as a line-filter capacitor in one of the components. Perhaps after 20 minutes of operation it then breaks down further, due to either heat or exposure to voltage, resulting in a leakage path between ac and chassis (which is usually common with signal ground, and in the case of components that have a 3-prong plug, is also common with ac safety ground).
Interconnects for single-ended (rca) interfaces tie the chassis of the connected components together electrically, so disconnecting and reconnecting them would conceivably have a relation to either stored charge or voltage stresses involving capacitance that is in electrical proximity to the ac line.
Also, it's very conceivable to me that a compromised line filter capacitor in one of the components would be the kind of thing that would not show up when you sent the components back to the manufacturers for them to check out.
Obviously I can't quite formulate all of this precisely, but the bottom line is that I am suspicious of the ac wiring and grounding, and that it may have caused effects something like these. I'm envisioning not only miswiring in the sense of interchanged connections, but also, perhaps, the possibility that an ac neutral run is open, creating a round-about return path involving interconnects, safety ground, and/or other components.
Regards,
-- Al
Behind my other suggestions was the thought that one of your ac runs may be miswired, which at some point in the past may have damaged a part such as a line-filter capacitor in one of the components. Perhaps after 20 minutes of operation it then breaks down further, due to either heat or exposure to voltage, resulting in a leakage path between ac and chassis (which is usually common with signal ground, and in the case of components that have a 3-prong plug, is also common with ac safety ground).
Interconnects for single-ended (rca) interfaces tie the chassis of the connected components together electrically, so disconnecting and reconnecting them would conceivably have a relation to either stored charge or voltage stresses involving capacitance that is in electrical proximity to the ac line.
Also, it's very conceivable to me that a compromised line filter capacitor in one of the components would be the kind of thing that would not show up when you sent the components back to the manufacturers for them to check out.
Obviously I can't quite formulate all of this precisely, but the bottom line is that I am suspicious of the ac wiring and grounding, and that it may have caused effects something like these. I'm envisioning not only miswiring in the sense of interchanged connections, but also, perhaps, the possibility that an ac neutral run is open, creating a round-about return path involving interconnects, safety ground, and/or other components.
Regards,
-- Al