3 blinks of Standby/power LED of Sony sets denotes a SMPS board [G-board] failure. . 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.
If blinks continue without any pause, the main board is faulty.
Search the site by type in the "brand name"
to your device, in the "Search box at the top right of the display window of the Homepage
" to get gathered related posts.