Try twisting the high voltage connector that fits in the top of the screen just a bit, the round thing that looks like a suction pad.
Wear gloves or something !! 10 000 volts !!
If you just play sound of the same khz as your games is the spot then visible, or going away?
And regular speaker shielding is not necessaraly shielding it from magnetism it is a quite open gauze and if it is non ferro
then it is not shielding anything.
Wiring of speakers are also electromagnetic, they are not running close to the screen are they?
Aluminium foil could help testing since it provides some shielding.
Edited by Garreth (04/26/12 11:25 AM)