My sony tv has sound but no picture and red light keeps blinking

Those blinks [flashes] are fault indication (Error Codes). From the number of blinks occur at one time switch ON, you can get an idea about the faulty circuit section inside it. This will make repair easy. These are called blinking codes. Make sure about the exact number of blinking of the standby/power LED, by switching On & OFF the set, for at least two times. Count it carefully. If you wish to get some details, check the site linked here. It has details about blinking codes, and fault locating procedure, to many popular brand TVs and other devices. https://elektrotricks.blogspot.com/
http://electronicshelponline.blogspot.com/
Type in the brand name of your device [exclude the model number] at the search box at the right column to get gathered related posts.
Blinking codes details to many popular brand TVs are given. If blinks continue without any pause, the main board is faulty.
Counting of number of blinks to Philips TVs is entirely different to that of other brand TVs. It is not a direct count procedure. The site have details about how to count the number of LED blinks [Fault Codes] to Philips brand TVs are given; along with details of the faulty circuit location