How to track bad parts (IC, transformer, resister etc) or cold solder joint in vertical deflection circuit ?

Question

Panasonic TV 27 inch model # CTG27.... shows single horizontal line at the center. With slight vibration or smack it performs well and again after few mins same problem.

Answer 1

If you aren't already comfortable with debugging electronic circuits, the high voltage of the vertical deflection circuit is no place to start.

There are numerous safety precautions that MUST be taken to make sure you don't get zapped while you're looking for the problem(s) -- too numerous and detailed to put here.

So -- take it to the local TV repair shop and expect a min $150-$200 bill or go for the HDTV that you really want anyway. That Panasonic TV will be obsolete in about 2 years (no more NTSC, only HDTV broadcasts), so you might as well bite the bullet and go for the HDTV now instead of dumping $200 into the old set.