KDL-46S504 won't come on; green light for 4-5 seconds then red standby light comes on and blinks 3 times, stops, then continues the blinking 3 times, etc,etc

SOURCE: Monitor shutting off with blinking standby light.

Very expensive to fix.You hve a bad ysus board.Nec will re-build theboards as a set 1000.00 plus

SOURCE: 42 in SONY LCD flat screen has red light blinking and won't turn on

Does the red light blink in a discernible pattern? How many times does it flash or blink?

SOURCE: standby light flashes 3 times

A 3 flash pattern indicates that either the lamp is not seated correctly or that the lamp door is not latched properly. It can also be a fault with the switches that sense whether the lamp is seated or the door is latched. Try reseating the lamp and relatching the lamp door

SOURCE: Sony KDF-E50A10 No Picture

4 times blink error shows that any FAN is not running in TV as there are 4 fans in this TV.
Please check fan connectors and make sure all are plugged securely.

SOURCE: Sony Bravia KDL 46", no picture, standby light blinks 4 times

Since the TV is still receiving power, the problem is going to be with the TV's mainboard.  After you unplugged the TV and plugged it back in, you said the power light went out again, so I assume the standby light wasn't flashing again?  The flashing standby light is indicating an error code so my suggestion is to contact Sony for service options regardless if there is a warranty or not because service is the only solution to this situation.  Don't forget to provide them the error code or 4 flashes repeating.