Benq G2420HDBL problem

[Jas1975]

Ordered both the 25th October - turned them on this morning and faced with this (with both monitors working perfectly since I got them) :

Photo taken with a blank notepad on both screens.

Anyone know what Benq / OCUK are like for replacing this kind of thing?

 

[Gypo]

Looks like interference, possibly electrical?

 

[Jas1975]

What I thought - however replacing all cables, moving the monitor, plugging it into a different PC with different cables - still the same.