Hello Tazmania, welcome, that happens to the Sonys of that made when the main source is burned, they have a double integrated MX transistor that is shorted, a resistance burns and stops walking, eye the horizontal transistor, only remains walking the standby source and does what you describe from the LED flashing

from here you can download the diagram
https://www.manualslib.com/manual/686916/Sony-Kv-36fs10.html#product-TRINITRON KV-38FX250
Tobias greetings