I can confirm that my broadband problems began in February which is when I started using the "noisy" monitor. Previously I had a HP monitor with a DVI connector, but it burnt out, so I had to replace it at short notice by borrowing the "noisy" monitor from work. Little did I know that it would cause me so much grief.
Opening the monitor and examining the capicitors is beyond my competence, so I will pass
on
Burak's request, apologies for that.
However, I am planning to buy a new monitor soon (maybe next month), so hopefully the problem will be resolved then. If not, I will return! In the meantime, I offer thanks to everyone who took time out to respond to this thread: your support was appreciated