Assumimg a horizontal line.
It's the most common fault symptom you'll get with a TV.
Usually, just a dry soldered joint to the frame output ic.
Expect a quick, cheap and simple repair.
Don't be tempted to run it while there's a line displayed. The fault will get more severe if left, so better to get it fixed sooner than later.
btw, if anyone tells you it's a faulty tube,.. take it elsewhere.
Cobweb
March 2007