I have sony triniton tv when i was turn on there is horizontal line on the center of screen this problem was never happen before

HI,
ur tv has problem with its vertical scanning side. vertical scanning output ic (integrated circuit ) may have some problem ( faulty or dry soldering in its leads). u can easily find out the vertical ic on ur tv. there will be four wire coming from the coil which is fitted on the picture tube neck, of which 2 will goto horizontal scanning section and the remaining two will go to vertical scanning section. just follow the two thin wire (normally in color green and yellow ). it will goto a socket on the main board. follow the track on the board. it will lead u to vertical scanning section. check for any dry soldering, if not , replace the ic.
ok