how can i fix it?

The problem you are describing appears to be a vertical circuit problem. You could have bad solder connections on the vertical output IC. You can inspect the PC board around the vertical IC to find out if that is where the issue lies. Call a technician to fix it for you if you can't do it yourself.
Here you are a technician website www.tvrepairjacksonvillefl.com
To know how much your repair costs, I would advise you to contact different repairers and dealers to compare the prices. This is because the cost will vary from one place to another

abel
August 2012