White horizontal lines across the top three inches of the screen. Is it worth fixing? Dynex 27" 480i standard definition digital TV

Replace all the electrolytic capacitors in the vertical output section circuit. There will be 5 or 6 of them. Replace the at one time. The fault you see is technically called " vertical retrace lies".

From your description it sounds like a vertical problem, the IC in the vertical sector may need to be resolded or replaced, there are 2 or 3 capacitors that should be checked that are very near the IC. This is a very common problem with Toshiba sets, and are worth getting repaired.

Check for dry electrolitic capacitors near the vertical Ic output maybe one of 50v to 100mf or 50v to 10mf

It sounds as though you can see Transmission lines which are sent out with any broadcast at the top of an image, The TV should normally blank these out, i suggest checking your horizontal and vertical settings

horiz.output IC going bad,need to replace it

go to the vertical section n change caps like 100uf, 2.2uf around the section in addtion check some caps in the line o/put like 22uf 250v

Check for open capacitors in vertical output circuit I believe 47 uf.

bad vertical chip ic

It sounds like a vertical deflection problem. You mentioned you had a white HORIZONTAL LINE in the middle of the screen. If this line runs from left to right across the screen it's in Verticla deflection. If it runs from top to bottom, it's in Horizontal deflection. I am assuming the problem is a Vertical deflaecion problem. The repairs necessary are most likley to replace the vertical capacitors or the verticla deflection chip.
Good Luck
Ed
NC Electronic Mills, Wyo USA

Dear simon, Seems like a simple problem. In all likelihood, one of the Electrolytic Capacitors in the vertical Output stages has failed.It could also be a cold / dry solder, as symptoms seem to disappear when you tap the set. But, do not try anything thing at home. A proffessional Techie should fix it up in 15-20 mins. Definitely worth the spend.