Some people think that as long as the set about the display settings on the line, indeed, if this phenomenon is caused by man, then as long as the tone on the line, but this situation does not occur almost - unless rookie in the rookie ^ _ ^. 

 

Cause and Countermeasures: 

 

The common point of failure is usually a line or field correction circuit there is a problem (such as s correction capacitors, etc.), because maintenance is to have a certain expertise, so I suggest you deliver appliance maintenance department for repair. Of course, if the fault is present in your operation to monitor what were after, then you can do some debugging first reference manual correction work try, as long as you can usually get a detailed read the manual! :)