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Monitor Won't Stay In Standby

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PhilippeV

First check the state of all cables and connectors (including those within the PC case), and their correct and complete insertion in their sockets/plugs, and the correct linking to ground and earth of all shields, including the shields of your video cable which should have a strong contact with the terminal connectors on both sides (some cables are incorrectly mounted and forget to connect these shields).

Beware also of silent blocks : they may isolate the screws that normally ensure the ground linking. And some screws may be painted with isolating material (like glue), or missing (so that not all grounds are fuly interconnected within the PC case).

Make sure that all internal devices are fixed with at least one screw on their grounded case (including PCI boards, disks and CD/DVD burners).

Any unused cable should not remain connected on one end: remove/disconnect those extra cables that are acting like amplified antennas, even if their gain is very small.

Unused cables should never exceed about 5 cm of length, otherwise it will capture a lot of long-range and highly penetrant VHF signals, with enough gain to generate an oscilation that will charge the circuits on your motherboards.

Also make sure that the monitor and PC have their A/C cable connected to earth (beware of cheap A/C outlet multipliers missing the ground-to-earth cable, if you live in an area with strong VHF emitters above the regulatory level of 57 dBm or 5V/m : this may happen if you're within about 50 meters from a strong GSM or FM radio antenna, or within 1 km of a TV emitter, or if you have incorrectly shielded neon lights, or within 300 meters of a high-power factory or railway station, or a high-voltage transformer in the street, which locally amplifies all the power spikes from the neighbourhood in the power grid).

Finally, make sure that you don't use any A/C wall sockets that were mounted in your home for high-power engines only protected by a 5 ampere fuse (such as oven, water heaters, wash machine...). For all your digital equipment, use only standard low power sockets (with 0.5A or 1.0A fuses).

Note that in rural areas, your electric supply may be delivered with 3 phases (this saves lots of energy within the long cables in your public power grid): in that case, your home installation normally distributes the power equally on each phase, and not all the wall sockets use the same phase. Normally, your home installaton includes a special "triangle-star" transformer to generate the point of ground that should be connected to earth, but some old installations are still missing this transformer. In that case, you don't have a solid ground-to-earth connection, and there's a constant oscillation between the phases, so that none of them are using the same ground. In that case, if your PC is connected to one wall socket, and your monitor to another one, they may have problems to stabilize their grounds which are constantly oscillating at 50/60Hz between each other, relative to the earth.

Only a qualified electrician will help diagnostic your old electric installation, and detect that you need the installation of the special transformer for connecting the low-power wall sockets and lights. (The electric heaters and high-power sockets won't use this transformer, but will be connected directly to the 3-phase supply, on separate sockets, via the 2-5 amperes fuses).

Don't mix multiple A/C wall sockets for digital devices that share any digital or analog signal connection via some cable (here the VGA or HDMI cable) ! Ideally the PC and monitor should share the same wall socket, but this could also be an audio cable to your Hifi system (and in frequent cases, the Hifi or flat TV will be on another wall socket : in that case, you may need to check that all sockets are effectively properly grounded to earth with the special transformer to avoid resonating oscillations between distinct phase-neutral pairs on your A/C outlets).

The special transformer above simplifies the connection because it will allow an interconnection of all neutral points of each phase-neutral pair in the triangular distribution, and this common neutral will also be grounded to earth in the transformer, before your home distribution to the various sockets of each phase. But beware also that the transformer may also be damaged with one circuit burnt (in that case the triangular mounting no longer equilibrates the power used across phases within the transformer, and grounding becomes unstable). This can create very powerful ERM levels everywhere in your home, which will be captured by every unshielded numeric cable (and you may see that your lights bulbs are burnt too often, or ou could see electric arcs each time you plug or unplug a cable on the sockets: call a qualified electrician to inspect the transformer, and note that your energy billing will rise very significantly if you don't repair it).