Recently, I faced a weird problem. While watching television, if the computer (in the same room) was started, the TV ended up with a distorted picture and a big sound – effectively ruining the TV watching experience. While that was a good thing for the family – making the operations of the PC and the TV mutually exclusive – it was an unworkable situation.
After referring a few electricians, they replied that this might be because of the surge of electricity when the PC was switched on.
To add to the misery, once when I started the PC, while the TV was operating, it created noise. Then I switched off the TV, pulled around a few wires, separating the cable TV wire from near the power cable, the interference on the TV vanished.
But my hope was short lived. This mutually agreeable operation worked only for two days and that too, over the weekend. Then the situation went back to normal – distortion while operating the PC.
In the meantime, I noted that the TV made the same sound, but at a very less level – usually masked by the volume of the TV program. When I muted the TV, I could hear the small sound.
Yesterday, I referred another electrician. After much pulling at cables and opening electric panels, he located the source of the problem. During this exercise of identifying the problem, we noted that if the TC was operating while the PC was also operating, BUT the set-top box was switched off, there was not interference on the TV. Hence we realized that the problem could be due to the set-top box.
Then the electrician tested the set-top box and checked its earthing – that solved the problem. As it happens, the set-top box is not earthed/grounded properly. Once he added a wire from the set-top box and connected it to the ground of the socket, the problem of the sound and also appearance of scan lines on the TV vanished.