If Your screen shows a: white vertical line on a black screen or, a white horizontal line on a black screen:
Your TV vertical or, horizontal power transistor or, chip is getting too hot.
A vertical line indicates the horizontal circuit is at fault, a horizontal line indicates the vertical circuit is at fault.
To troubleshoot: Turn on your TV
untill the line shows then: after about a minute, remove power (unplug) the TV, remove the TV back cover, find the too hot transistor or, chip; using component coolant; spray the too hot component with the component cooler until the screen comes back to normal. To fix: apply white coolant cream to the back of the too hot transistor or, chip
. or, if there is room, a small fan can be wired in to cool the part. Radioshack sells the cream and, also a "component cooler spray" that should find and, fix this problem, also; with power removed you can, if you feel it is safe; carefully (with only one hand) feel the part; it will be very hot! (it could burn your finger!) Do not touch anything else! (this will not hurt the tv; when the picture comes back on (the offending part has cooled) you have found the problem part.