There are pieces of black screen

The upper left corner in the lower right corner of the screen or black pieces, about handkerchiefs as the pieces of paper as such a big, run the same, the black pieces on the screen began to fade away, to disappear from the emergence of about three minutes now, this is How the case, it is a virus, or display of thing? Please tell me

This is not a general phenomenon caused by the virus .
rule out the picture tube in question (your picture tube is good) is the general failure of electronic circuits.
first check degaussing circuit, the focus of inspection is not degaussing resistance leakage (down to look at it there is no black spot But this time there is a general color blocks appear).
Further investigation deflection circuit, the search focused on the output circuit, such as missing frames output capacitor capacity, the output capacitor circuit capacity, and so on, and then check deflection coil is not a loosening of the phenomenon.
check in the third frame output circuit of the circuit incentives, the focus is not there to see electrolytic capacitor is drying up.
Fourth, the other circuits, focusing on power check (display) circuit has lost capacity capacitor, such as damage to the resistance phenomenon.